Advanced Pathophysiology Advanced Pathophysiology., Exams of Pathophysiology

Download Advanced Pathophysiology Advanced Pathophysiology. and more Exams Pathophysiology in PDF only on Docsity! Advanced Pathophysiology Absolute polycythemia - excessive red blood cell production; a physiologic response resulting from increased erythropoietin secretion in response to chronic hypoxia or as a symptom of polycythemia vera. Absorption atelectasis - see Atelectasis. Acid maltase deficiency (glycogen storage disease type II or Pompe disease) - an autosomal recessive metabolic disorder that damages muscle and nerve cells throughout the body by an accumulation of glycogen in the lysosome attributable to deficiency of the lysosomal acid a-glucosidase enzyme. The buildup of glycogen causes progressive muscle weakness (myopathy) throughout the body and affects various body tissues, particularly in the heart, skeletal muscles, liver, and nervous system. Acne - a common skin disease characterized by pimples on the face, chest, and back. It occurs when the pores of the skin become clogged with oil, dead skin cells, and bacteria. Acne conglobata - severe cystic acne characterized by cystic lesions, abscesses, communicating sinuses, and thickened, nodular scars; usually does not affect the face. Acne rosacea - a chronic form of dermatitis of the face in which the middle portion of the face appears red with small red lines caused by dilation of capillaries. Acne vulgaris - an inflammatory eruption of the sebaceous follicles usually occurring on the face, upper back, and chest that consists of blackheads, cysts, papules, and pustules. Noninflammatory acne - open comedones caused by the enlargement and dilation of a plug resulting from the accumulation of oil and dead skin cells inside the hair follicle and by closed comedones that form if the hair follicle pore remains closed; they appear as a tiny, sometimes pink bump in the skin. Acquired immunodeficiency syndrome (AIDS) - see Immune deficiency. Acquired sideroblastic anemia - see Anemia. ACTH deficiency - a condition characterized by decreased or absent production of adrenocorticotropic hormone (ACTH) by the pituitary gland, resulting in a reduction in the secretion of adrenal hormones and subsequent weight loss, lack of appetite, weakness, nausea, vomiting, and low blood pressure. Actinic keratosis - a condition in which a premalignant small, reddish, rough spot appears on skin chronically exposed to the sun. Acute chest syndrome - a syndrome occurring in association with sickle cell disease defined by a new infiltrate on chest radiograph; associated with one or more new symptoms: fever, cough, sputum production, dyspnea, or hypoxia. It occurs most commonly in the 2- to 4-year-old age group and declines in incidence with age. Acute colonic pseudo-obstruction (Ogilvie syndrome) - a massive dilation of the large bowel that occurs in critically ill patients and immobilized older adults. It is characterized by significant dilation of the cecum and absence of mechanical obstruction, and is related to excessive sympathetic motor input or decreased parasympathetic motor input. Acute confusional state (ACS) - a form of delirium caused by interference with the metabolic or other biochemical processes essential for normal brain functioning. Symptoms may include disturbances in cognition and levels of awareness, short-term memory deficit, retrograde and anterograde amnesia, and disturbances in orientation, accompanied by restlessness, apprehension, irritability, and apathy. The condition may be associated with an acute physiologic state, delirium, toxic psychosis, or acute brain syndrome. Acute coronary syndrome - a classification encompassing clinical presentations ranging from unstable angina through infarction. Acute cystitis - an inflammation of the bladder, which is the most common site of urinary tract infection. Acute epiglottitis - an infection that causes inflammation of the epiglottis and surrounding tissues and may lead to upper airway blockage. Acute gastritis - an inflammatory disorder of the gastric mucosa, usually caused by injury of the protective mucosal barrier by drugs, chemicals, or Helicobacter pylori infection. Acute glomerulonephritis - see Glomerulonephritis. Acute gouty arthritis - an abrupt pain of a joint, most often the great toe, which is swollen, hot, and shiny secondary to an attack of gout. Akinesia - slowness or loss of normal motor function resulting in impaired muscle movement. Akinetic mutism (AM) - a syndrome characterized by the inability to speak, loss of voluntary movement, and apparent loss of emotional feeling. It is related to lesions of the upper brainstem. Albright syndrome (Albright-McCune-Sternberg syndrome) - a syndrome characterized by polyostotic fibrous dysplasia, patchy dermal pigmentation, and endocrine dysfunction. Alcoholic cirrhosis - see Cirrhosis. Alcoholic fatty liver (steatosis) - the mildest form of alcoholic liver disease; can be caused by chronic ingestion of relatively small amounts of alcohol, may be asymptomatic, and is reversible with cessation of drinking. Alcoholic hepatitis (steatohepatitis) - a precursor of cirrhosis characterized by inflammation; degeneration and necrosis of hepatocytes; infiltration of neutrophils, macrophages, and lymphocytes; immunologic alterations; and lipid peroxidation. Algor mortis - postmortem reduction of body temperature. Alkaline reflux gastritis - inflammation of the stomach caused by reflux of bile and alkaline pancreatic secretions that contain proteolytic enzymes and disrupt the mucosal barrier in the remnant stomach. Allergic contact dermatitis - contact dermatitis attributable to allergic sensitization. Allodynia - a condition in which pain arises from a stimulus that would not normally be experienced as painful. Allostasis - long-term or chronic exaggerated responses to stress. Alogia - inability to speak because of mental deficiency, mental confusion, or aphasia. Alopecia - loss of hair. Alopecia areata - an autoimmune T-cell-mediated chronic inflammatory disease directed at hair follicles that results in baldness, usually in round patches. Alpha-thalassemia major - see Anemia. Alpha-thalassemia minor - see Anemia. Alzheimer disease (dementia of Alzheimer type [DAT], senile disease complex) - a degenerative disease characterized by amyloid plaques and fibrillary tangles in the cortex and atrophy and widened sulci in the frontal and temporal lobes. Amblyopia - poor vision caused by abnormal development of visual areas of the brain in response to abnormal visual stimulation during early development. Amenorrhea - lack of menstruation; most common causes (aside from pregnancy) are chromosomal abnormalities, hypothalamic dysfunction, polycystic ovarian syndrome, hyperprolactinemia, hypothyroidism, malnutrition, and ovarian failure. Amyotrophic lateral sclerosis (ALS) (sporadic motor system disease, sporadic motor neuron disease, motor neuron disease, Lou Gehrig disease) - a disease that breaks down tissues in the nervous system (a neurodegenerative disease); it is of unknown cause and affects the nerves responsible for movement. Anaphylactic shock - a state of shock caused by a severe allergic reaction that lowers blood pressure and results in urticaria, breathing difficulties, and possibly death. Anaphylactoid purpura (allergic purpura, Henoch-Schönlein purpura) - nonthrombocytopenic purpura attributable to immune hypersensitivity to foods, drugs, and insect bites. Anemia - hemoglobin concentration is less than normal because of a deficiency in red blood cells, a low level of hemoglobin in cells, or both; it manifests as pallor of the skin and mucous membranes, weakness, dizziness, easy fatigability, and drowsiness caused by oxygen deficiency. Congenital hemolytic anemias - Alpha-thalassemia major - thalassemia in which all four a chains of hemoglobin are defective, resulting in a fatal condition because oxygen cannot be released to the tissues. Alpha-thalassemia minor - thalassemia in which two a chains of hemoglobin are defective. Beta-thalassemia major (Cooley anemia) - thalassemia in which a-chain synthesis and ß-chain synthesis are uncoupled; ß-chain production is depressed moderately in the heterozygous form, beta-thalassemia minor, and severely in the homozygous form, beta-thalassemia major, resulting in erythrocytes that have a reduced amount of hemoglobin and accumulations of free a chains. Beta-thalassemia minor - see above. Glucose-6-phosphate dehydrogenase (G6PD) deficiency - an inherited condition that is asymptomatic in the absence of exposure to particular substances such as certain medicines, mothballs, or severe infections; with exposure the red blood cells undergo destruction, producing excessive bilirubin that overloads the liver and causes jaundice. Hemoglobin H disease - a form of alpha-thalassemia in which a hemoglobin H gene is expressed but cannot bind oxygen. Hereditary spherocytosis (congenital hemolytic anemia, congenital acholuric jaundice) - a defect in the cell membrane of red blood cells that causes thickened, fragile red blood cells that are susceptible to spontaneous hemolysis and results in chronic anemia, jaundice, fever, and abdominal pain. Sickle cell anemia (sickle cell disease [SCD]) - an inherited autosomal recessive disorder of the blood caused by abnormal hemoglobin that distorts red blood cells and makes them fragile and prone to rupture and can cause anemia, joint pain, fever, leg ulcers, and jaundice. Sickle cell-Hb C disease - a heterozygous form in which the child simultaneously inherits a hemoglobin C gene from another parent. Sickle cell-thalassemia disease - a heterozygous form in which the child simultaneously inherits a thalassemia gene from another parent. Sickle cell trait - an inherited condition in which an individual carries only one gene for sickle cell disease and is without symptoms. Thalassemia - a potentially fatal genetic disorder in which hemoglobin molecules are abnormal, resulting in severe anemia; enlarged heart, liver, and spleen; and skeletal deformation. Macrocytic anemia (megaloblastic anemia) - a condition characterized by erythrocytes that are larger than normal; associated with deficiency of vitamin B12 or folic acid caused by inadequate intake or insufficient absorption secondary to alcoholism or drugs that inhibit DNA replication. the most common form of autoimmune hemolytic anemia; caused by IgG that binds to erythrocytes at normal body temperature; often secondary to other diseases, especially lymphomas, chronic lymphocytic leukemia, other neoplastic disorders, or systemic lupus erythematosus (SLE). Anencephaly - anomaly in which the soft, bony component of the skull and much of the brain are missing. Angelman syndrome (happy puppet syndrome) - an inherited syndrome of jerky puppet like movements, frequent laughter, mental and motor retardation, peculiar open-mouthed facies, and seizures. Angina pectoris - chest pain caused by reduced cardiac blood flow and myocardial ischemia. Anhedonia - absence of pleasure from the performance of acts that would ordinarily be pleasurable. Ankylosing spondylitis (AS, spondyloarthritis) - chronic inflammation of the spine and sacroiliac joints with gradual fusion of the vertebrae that immobilizes the spine. Anorexia nervosa (AN) - a disorder with both psychologic and physiologic components that begins with dieting to lose weight and manifests into an inappropriate self-control behavior; continued restrictive eating may lead to starvation and eventually death. Anorgasmia (orgasmic dysfunction) - the inability of the woman to reach or achieve orgasm. Anuria - urine output less than 50?mL/day. Anxiety disorder - a group of disorders involving various manifestations of anxiety that are grouped together and include panic disorder, specific phobia, social phobia, obsessive-compulsive disorder (OCD), posttraumatic stress disorder (PTSD), acute stress disorder, generalized anxiety disorder (GAD), and anxiety disorders secondary to medical conditions or substance-induced or not otherwise specified. Aplastic anemia - see Anemia. Aplastic crisis - see Anemia. Appendicitis - inflammation of the appendix as a result of blockage of the opening from the appendix into the cecum; the appendix wall becomes infected and ruptures, allowing the infection to spread throughout the abdomen and cause pain, anorexia, fever, nausea, vomiting, and diarrhea. Apraxia - a disorder of voluntary movement consisting of impairment of the performance of skilled or purposeful movements; results from acquired cerebral disease. Arcus senilis - a gray to white ring at the periphery of the cornea; caused by deposits of cholesterol in the cornea or hyaline degeneration and occurs primarily in older persons. Areflexia - absence of reflexes. Arterial ischemic stroke (pediatric arterial ischemic stroke) - a rare disorder in children resulting from embolism, arteriopathy, or, rarely, sinovenous thrombosis and leading to a decreased flow of blood and oxygen to areas of the brain. Asbestosis - pulmonary inflammation and fibrosis resulting from inhalation of hydrous silicates of various metals in fibrous form. Aseptic meningitis - a form of inflammation of the meninges and subarachnoid space surrounding the brain and spinal cord without evidence of bacterial infection; may be associated with viral infection, systemic disease, or drugs. Aspiration pneumonitis - a condition caused by the abnormal entry of fluids, particulate matter, or secretions into the lower airways that can lead to chemical pneumonitis from entry of toxic material such as gastric acid, from bacterial infection, or by mechanical obstruction of the lower airways. Asthma - a chronic inflammatory disorder of the airways involving bronchial hyperresponsiveness and airway obstruction marked by periodic attacks of wheezing, shortness of breath, a tight feeling in the chest, and a cough that produces mucus because of an allergic reaction triggered by certain drugs, irritants, viral infection, exercise, or emotional stress. Asymptomatic bacteriuria - the presence of bacteria in the urine without evidence of infection. Ataxia-telangiectasia (AT) - see Immune deficiency. Ataxic cerebral palsy - a form of cerebral palsy associated with damage to the cerebellum and resulting in gait disturbances and instability; at birth the infant may have hypotonia, but develops stiffness of the trunk muscles later in infancy. Atelectasis - part of or an entire lung collapses and the alveoli deflate as a result of surgery, smoking, or blockage of a bronchiole. Absorption atelectasis - collapse of lung tissue resulting from gradual absorption of air from obstructed or hypoventilated alveoli or from inhalation of concentrated oxygen or anesthetic agents. Compression atelectasis - air pressure in the pleural space pushes against the already recoiled lung, causing compression atelectasis, and against the mediastinum, compressing and displacing the heart and great vessels. Surfactant impairment - decreased production or inactivation of surfactant, which is necessary to reduce surface tension in the alveoli and causes lung collapse during expiration; can occur because of premature birth, acute respiratory distress syndrome, anesthesia, or mechanical ventilation. Atherosclerosis - a type of arteriosclerosis in which the inflammatory changes of thickening and hardening of the walls of large- and medium-sized arteries are caused by an atheroma or plaque of lipids, cells, and connective tissue in the tunica intima. Atopic dermatitis (AD) (allergic dermatitis) - a chronic hereditary skin disease characterized by intense itching and inflamed skin that causes redness, swelling, cracking, crusting, and scaling. Atrial septal defect (ASD) - a congenital heart disease involving the interatrial septum of the heart that separates the right and left atria, which results in misdirected blood flow between the two sides of the heart. Atrioventricular canal (AVC) defect - a large hole is present in the center of the heart where the wall between the atria joins the wall between the ventricles, and the tricuspid and mitral valves are formed into a single large valve that crosses the defect. Atypical ductal hyperplasia (ADH) - abnormal proliferating cells in breast ducts. Atypical hyperplasia - increased number of cells with some variation in cellular structure but without sufficient qualitative or quantitative features of carcinoma. Atypical lobular hyperplasia (ALH) - abnormal proliferating cells in breast lobules. Autoimmune hemolytic anemia (AIHA) - see Anemia. Autoimmune neonatal thrombocytopenia - see Thrombocytopenia. Blepharitis - inflammation of the eyelids. B-lymphocyte deficiency - see Immune deficiency. Bradycardia - an abnormally low heart rate, which can cause a fall in cardiac output or can be a symptom of deterioration. Bradykinesia - decreased spontaneity and movement; a feature of extrapyramidal disorders, such as Parkinson disease. Brainstem gliomas - a group of tumors located in the brainstem that are usually classified as high grade and result in the sudden onset of symptoms including headaches, vomiting, and visual disturbances. Bronchial carcinoid tumor - an obstructing tumor of the trachea or large bronchi that may cause paraneoplastic symptoms. Bronchiectasis - dilation of the bronchi in response to obstruction, necrotizing pneumonias, cystic fibrosis, or Kartagener syndrome (a hereditary syndrome consisting of dextrocardia, bronchiectasis, and sinusitis). Bronchiolitis - inflammation of the bronchioles usually caused by viral infection. Bronchiolitis obliterans - partial or complete obliteration of bronchioles and some bronchi by granulation and fibrotic tissue masses. Bronchiolitis obliterans with organizing pneumonia (BOOP) - obstruction of the bronchioles and alveolar ducts by fibrous granulation tissue that is further complicated by the development of pneumonia. Bronchopulmonary dysplasia (BPD) - a condition most often found in premature infants in which chronic pulmonary insufficiency occurs because of long-term artificial pulmonary ventilation. Bruton agammaglobulinemia - see Immune deficiency. Bulbar palsy - a form of palsy resulting from impaired function of the cranial nerves from degeneration of the motor neurons of primarily the brainstem; manifested as weakness and wasting of the various bulbar muscles, resulting in difficulty articulating words (dysarthria) and difficulty swallowing (dysphagia); fluid regurgitation is a major symptom and can cause aspiration. Bullous pemphigoid (BP) - a more benign autoimmune disease than pemphigus vulgaris, with blistering of the subepidermal skin layer. Burkitt lymphoma - see Lymphoma. Burn shock - a phenomenon consisting of both a hypovolemic cardiovascular component and a cellular component; results from massive fluid losses from the circulating blood volume. Bursitis - a trauma or overuse injury that can cause painful inflammation in the bursal sacs. C1 deficiency - see Immune deficiency. C2 deficiency - see Immune deficiency. C3 deficiency - see Immune deficiency. C3 receptor deficiency - see Immune deficiency. C4 deficiency - see Immune deficiency. C9 deficiency - see Immune deficiency. Cachexia - illness and malnutrition seen in individuals with cancer that results in wasting and eventual death. Calculi or urinary stone (urolithiasis) - masses of crystals, protein, or other substances that are a common cause of urinary tract obstruction in adults. Candidiasis - a fungal infection caused by an overgrowth of normal Candida albicans found in the skin and mucous membranes of the mouth, respiratory tract, or vagina. Caplan syndrome - formation in coal workers of intrapulmonary nodules in pneumoconiosis that are histologically similar to subcutaneous rheumatoid nodules associated with rheumatoid arthritis. Carbuncles - a condition in which a bacterial infection of the hair follicle or sebaceous gland ducts becomes painful and discharges pus through various openings. Carcinoma - epithelial cell tumor. Carcinoma in situ (CIS) - preinvasive epithelial malignant tumors of glandular or squamous cell origin. Cardiogenic shock - a condition resulting from decreased cardiac output caused by heart disease in which the heart is unable to pump blood through the body, usually because of myocardial infarction. Cardiomyopathy(ies) - a diverse group of diseases primarily affecting the myocardium and resulting from tissue remodeling caused by myocardial and neurohumoral responses to ischemic and hypertensive alterations. Cavernous (congenital) hemangioma - a birthmark that is similar to the strawberry hemangioma but is more deeply rooted and may appear as a red-blue spongy mass of tissue filled with blood. Cellulitis - an infection of the dermis and subcutaneous tissue usually caused by Staphylococcus, CA- MRSA, or group B streptococci. Central core disease (CCD) - an autosomal dominant congenital myopathy characterized by hypotonia, delay of motor development in infancy, and nonprogressive or slowly progressive muscle weakness; on biopsy the central core of muscle fibers stains abnormally, myofibrils are abnormally compact, and there is virtual absence of mitochondria and sarcoplasmic reticulum; histochemically, the cores are devoid of oxidative enzyme, phosphorylase, and ATPase activity. Central precocious puberty - a condition in which puberty begins prematurely with normal changes in the hypothalamus- pituitary-gonad (HPG) axis and with premature development of secondary sexual characteristics and premature closure of the epiphysis of long bones, resulting in lifelong short stature. Centriacinar emphysema - see Emphysema. Cerebellar astrocytoma - brain tumor of the right or left cerebellar hemisphere that causes motor symptoms on the same side as the tumor. Cerebral palsy (CP) - a developmental brain injury that occurs before or shortly after birth and causes muscular impairment affecting motor function and also may alter speech and learning abilities. inflammation of the pancreas resulting from repeated exacerbations of acute pancreatitis that lead to chronic changes; associated with obstruction from gallstones, autoimmune disease, gene mutations, smoking, occupational chemical exposure, and obesity. Chronic pyelonephritis - persistent or recurrent infection of the kidney leading to scarring. Chronic relapsing thrombotic thrombocytopenic purpura (TTP) - see Thrombocytopenia. Chronic venous insufficiency (CVI) - persistent ambulatory lower extremity venous hypertension. Cirrhosis - degeneration of liver tissue resulting in fibrosis with nodule and scar formation that compromises liver function. Alcoholic cirrhosis - destructive inflammation of the liver caused by the toxic effects of alcohol metabolism, immunologic processes, lipid peroxidation, and malnutrition. Biliary cirrhosis - a form of alcoholic cirrhosis in which damage and inflammation leading to cirrhosis begin in bile canaliculi and bile ducts, rather than in the hepatocytes. Primary biliary cirrhosis - a T-lymphocyte- and antibody-mediated destruction of the small intrahepatic bile ducts. Cloacal exstrophy - family of congenital anomalies with two exstrophied bladder units separated by an exstrophied segment of intestine, which is usually cecum, receiving the ileum superiorly and continuing distally to a blind ending microcolon. Clubfoot - describes a range of foot deformities in which the foot turns inward and downward. Cluster headache - one of a group of rare disorders referred to as trigeminal autonomic cephalagia; they occur in clusters (up to eight attacks per day) on one side of the head primarily, with pain that is severe, stabbing, and throbbing. Coal worker pneumoconiosis (coal miner lung, black lung) - mild to severe pneumoconiosis (pulmonary fibrosis) caused by coal dust (coal, silica, quartz) deposits in the lung; symptoms initially present as a productive cough and wheezing, but may advance to chronic bronchitis and emphysema. Coarctation of the aorta (COA) - a condition in which the aorta narrows in the area where the ductus arteriosus inserts; narrowing usually occurs preductal in children and postductal in adults. Cold agglutinin autoimmune hemolytic anemia - see Anemia. Cold hemolysin autoimmune hemolytic anemia (paroxysmal cold hemoglobinuria) - see Anemia. Combined T- and B-lymphocyte deficiency - see Immune deficiency. Common variable immune deficiency - see Immune deficiency. Communicating (extraventricular) hydrocephalus - a disorder in which the cerebrospinal fluid pathways are intact but cerebrospinal fluid absorption is impaired. Community-acquired pneumonia (CAP) - a major cause of morbidity and mortality in children, particularly in developing countries. Complement deficiency - see Immune deficiency. Complete precocious puberty - refers to the early onset and progression of all pubertal features (i.e., thelarche, pubarche, and menarche). Complex febrile seizure - seizures with characteristic features similar to those of simple febrile seizure with a longer duration and focal characteristics; occur more than once in a 24-hour period. Complex regional pain syndrome (CRPS) - diffuse persistent pain usually in an extremity often associated with vasomotor disturbances, trophic changes, and limitation or immobility of joints; frequently follows a local injury. Compression atelectasis - see Atelectasis. Compressive syndrome (sensorimotor syndrome; crush syndrome) - a shocklike state that follows release of a limb (or limbs) or the trunk and pelvis after a prolonged period of compression, such as by a heavy weight; characterized by suppression of renal function, probably the result of damage to the renal tubules by myoglobin from the damaged muscles. Congenital adrenal hyperplasia - a group of autosomal recessively inherited disorders associated with a deficiency of one of the enzymes involved in cortisol biosynthesis, resulting in elevation of ACTH levels and overproduction and accumulation of cortisol precursors proximal to the block; androgens are produced in excess, causing virilization. The most common disorder is the 21-hydroxylase deficiency, caused by mutation in the cytochrome P450 21-hydroxylase gene (CYP21) on chromosome 6p. Congenital aganglionic megacolon (Hirschsprung disease) - a congenital defect in which the nerves that innervate the anus through the wall of the bowel are absent, resulting in enlargement of the bowel superior to the point where the nerves are missing and a subsequent decrease in peristalsis that results in chronic constipation. Congenital hydrocephalus - excessive accumulation of cerebrospinal fluid present at birth and characterized by increased intracranial pressure (ICP). This increase may be caused by a blockage within the ventricular system in which the CSF flows, an imbalance in the production of CSF, or a reduced reabsorption of CSF that results in ventricular enlargement and increased ICP. Congenital hypothyroidism - lack of secretion of thyroid hormone. Congenital (infantile) nephrotic syndrome (Finnish type) - a very rare form of nephrotic syndrome caused by a defect in a kidney protein resulting in excessive amounts of protein excreted in the urine. Congestive splenomegaly - enlargement of the spleen accompanied by ascites, portal hypertension, and esophageal varices; most commonly seen in those with hepatic cirrhosis. Consumptive thrombohemorrhagic disorders - heterogeneous group of conditions that demonstrate the entire range of hemorrhagic and thrombotic pathologic conditions. Contact dermatitis - an allergic response to an environmental antigen binding to specific carrier proteins contained in an individual's skin. Contrecoup injury - brain injury resulting from the brain hitting the inside of the skull on the side opposite the site of blunt force trauma. Cor pulmonale - right-sided heart failure caused by prolonged pulmonary hypertension. Coronary artery disease (CAD) - narrowing of the lumen of one or more of the coronary arteries, usually attributable to atherosclerosis, leading to myocardial ischemia; can cause congestive heart failure, angina pectoris, or myocardial infarction. Craniopharyngioma - a brain tumor that develops in the pituitary gland and most often affects children, causing headache, seizure, diabetes insipidus, early onset of puberty, and delayed growth. Craniosynostosis (craniostenosis) (see Syndromic craniosynostosis) - diseases having in common the triad of symptoms of polyuria, weight loss, and significant glucosuria. Diabetes insipidus - a disease caused by a deficiency in or resistance to antidiuretic hormone that is characterized by excretion of large amounts of dilute urine because of a decrease in water reabsorption in the kidney. Gestational diabetes mellitus (GDM) - carbohydrate intolerance of variable severity with onset during pregnancy. Type 1 diabetes mellitus - a disorder of carbohydrate metabolism characterized by a decrease in insulin production, resulting in hyperglycemia, ketoacidosis, and eventually renal failure and coronary artery disease. Type 2 diabetes mellitus - a condition of glucose intolerance that normally appears first in adulthood and is exacerbated by obesity and an inactive lifestyle. Maturity-onset diabetes of youth (MODY) - a non-insulin-requiring diabetes in lean individuals typically younger than 25 with evidence of autosomal dominant inheritance. Diabetic nephropathy - a progressive kidney disease caused by diabetes-induced angiopathy of capillaries in the glomeruli that causes nodular glomerulosclerosis. Diabetic neuropathy - combined sensory and motor disorder often seen in older diabetic patients as a result of microvascular injury involving small blood vessels that supply nerves. Diabetic retinopathy - damage to the retina caused by an overaccumulation of glucose or fructose that damages the blood vessels in the retina; in advanced stages, lack of oxygen in the retina causes fragile blood vessels to grow along the retina and in the vitreous fluid of the eye that may bleed and cause blurred vision. Diaper dermatitis - a type of dermatitis characterized by inflammation of the skin in the diaper area in infants caused by exposure of the skin to feces and urine. Diastolic heart failure - a condition in which heart contractions are normal but the ventricle does not relax completely; therefore less blood enters the heart. Diffuse brain injury (diffuse axonal injury) - injury to neuronal axons in many areas of the brain caused by stretching and shearing forces received during brain injury. DiGeorge syndrome - see Immune deficiency. Dilated cardiomyopathy (congestive cardiomyopathy) - a condition in which all four chambers of the heart are enlarged and weakened, resulting in progressive congestive heart failure and the need for heart transplantation. Discoid (cutaneous) lupus erythematosus (DLE) - see Lupus erythematosus. Dislocation - the temporary displacement of a bone from its normal position in a joint. Disorders of desire (hypoactive sexual desire, decreased libido) - the most common sexual dysfunction in women; prevalence increases with age and may be a biologic manifestation of depression, alcohol or other substance abuse, prolactin-secreting pituitary tumors, or testosterone deficiency. Disseminated intravascular coagulation (DIC) - an acquired clinical syndrome characterized by widespread activation of coagulation resulting in formation of fibrin clots in medium and small vessels (microvasculature) throughout the body. Distal intestinal obstruction syndrome (DIOS) - a syndrome seen in cystic fibrosis secondary to impaction with feces and inspissated mucus. Diverticulitis - inflammation of the herniations or saclike outpouchings of mucosa through the muscle layers of the colon wall. Diverticulosis - the presence of multiple bulging sacs pushing outward from the wall of the large intestine that may become infected and rupture, causing abdominal pain, tenderness, and fever. Down syndrome - trisomy or translocation of chromosome 21, resulting in intellectual disability; distinctive facial appearance with a low nasal bridge, epicanthal folds, protruding tongue, and flat, low-set ears; poor muscle tone (hypotonia); and short stature. Congenital heart defects, reduced ability to resist respiratory tract infections, and increased risk for leukemia are common. Drug-induced hemolytic anemia - see Anemia. Duchenne muscular dystrophy (DMD) - an X-linked genetic disorder in which fat and fibrous tissue infiltrate and weaken muscle tissues such as in the legs and pelvis, lungs, and heart; usually results in death before adulthood. Dumping syndrome - rapid emptying of hypertonic chyme from a surgically created residual stomach causing nausea, vomiting, bleeding, and diarrhea about 20 minutes after a meal. Duodenal ulcer - most common type of peptic ulcer; usually associated with altered mucosal defenses, rapid gastric emptying, elevated serum gastrin levels, or acid production stimulated by smoking. Dysfunctional uterine bleeding (DUB) - heavy or irregular bleeding in the absence of organic disease, such as submucous fibroids, endometrial polyps, blood dyscrasias, pregnancy, infection, or systemic disease. Dyskinetic cerebral palsy - extreme difficulty in fine motor coordination and purposeful movements resulting from injury to the basal ganglia or thalamus. Dysphoric mood - mood of general dissatisfaction, restlessness, depression, and anxiety; a feeling of unpleasantness or discomfort. Dysplasia (atypical hyperplasia) - abnormal changes in the size, shape, and organization of mature cells; considered a form of atypical hyperplasia. Dyspraxia - the partial inability to perform purposeful or skilled motor acts in the absence of paralysis, sensory loss, abnormal posture and tone, abnormal involuntary movement, incoordination, or inattentiveness. Dysrhythmias (arrhythmias) - disturbances of cardiac rhythm and the most common complication of acute MI. Dyssynergia - development of lesions in the upper motor neurons of the brain and spinal cord; results in loss of coordinated neuromuscular contraction and overactive or hyperreflexive bladder function. Eczema - most common inflammatory disorder of the skin; generally characterized by pruritus, lesions with indistinct borders, and epidermal changes. Eisenmenger syndrome - a progressively developing condition in which a congenital heart defect such as ventricular septal defect is left untreated and causes a reversed right-to-left shunt secondary to increased pressures on the right side of the heart because of pulmonary hypertension. Embryonic tumor - a tumor originating in the gestational period that contains predominantly immature blast cells that cannot differentiate into mature functional cells. Emphysema - pulmonary inflammation resulting in increased work of breathing or physiologic dead space and abnormal permanent enlargement of gas-exchange airways (acini) accompanied by destruction of alveolar walls without obvious fibrosis. Fanconi anemia - see Anemia. Fetal alcohol syndrome (FAS) - a syndrome of altered prenatal growth and morphogenesis that occurs in infants born to women who were chronically alcoholic during pregnancy; it includes maxillary hypoplasia, prominence of the forehead and mandible, short palpebral fissures, microphthalmia, epicanthal folds, severe growth retardation, intellectual disability, and microcephaly. Fibromyalgia - a condition in which muscles, tendons, and joints are painful, stiff, and tender; often accompanied by restless sleep, fatigue, anxiety, depression, and disturbances in bowel function. Fibrosarcoma - a malignant tumor of fibrous connective tissue that usually is derived from immature proliferating fibroblasts. Fibrous dysplasia (FD) - a genetic disorder in which tumor-like growths or lesions form in one or more bones and replace the medullary bone with fibrous tissue, resulting in expansion and weakening of the bone. Florid hyperplasia - rapid and unexpected cell growth in the lining of the breast ducts. Focal segmental glomerulosclerosis (FSGS) - a condition in which glomerular capillaries with thickened basement membranes and increased mesangial matrix collapse in segments. Usually presents as nephrotic syndrome. Frontotemporal dementia (FTD) (Pick disease) - progressive circumscribed cerebral atrophy; a rare type of cerebrodegenerative disorder manifested primarily as dementia, in which there is striking atrophy of portions of the frontal and temporal lobes. FSH deficiency - a condition characterized by decreased or absent production of follicle-stimulating hormone (FSH), resulting in a decline in spermatogenesis/oogenesis and associated infertility. Furuncles - a staphylococcal infection produces painful pus-filled inflamed hair follicles and involves surrounding skin and subcutaneous tissue. Fusiform aneurysm (giant aneurysm) - a large aneurysm that stretches to affect the entire circumference of the arterial wall. Galactorrhea (inappropriate lactation) - a condition in which milk-like fluid is secreted from the breast because of hormonal alterations that are not associated with childbirth or nursing. Ganglioneuroblastoma - an embryonal aggressive tumor of intermediate cellular differentiation that originates outside the CNS in the developing sympathetic nervous system. Ganglioneuroma - a benign neoplasm composed of mature ganglionic neurons scattered within a stroma of neurofibrils and collagenous fibers. Gangliosidosis - any disease characterized by abnormal accumulation of specific gangliosides within the nervous system (e.g., Tay-Sachs disease). Gastroesophageal reflux disease (GERD) - the reflux of acid and pepsin from the stomach to the esophagus that causes esophagitis. General adaptation syndrome (GAS) - the sum of all nonspecific reactions of the body to prolonged systemic stress, comprising alarm, resistance, and exhaustion. Generalized anxiety disorder (GAD) - an anxiety disorder characterized by an excessively anxious mood lasting at least 1 month that interferes with daily functioning and may be accompanied by jitteriness, sweating, feelings of catastrophe concerning one's family or self, and irritability. Generalized neuropathy - a functional disturbance or pathologic change in the cell body of one type of peripheral neuron. Genital herpes - a sexually transmitted viral infection that is caused primarily by herpes simplex virus type 2 and is characterized by painful lesions in the genital and anal regions. Gestational diabetes mellitus (GDM) - see Diabetes. GH deficiency - a condition characterized by decreased or absent production of growth hormone (GH), resulting in a decline in insulin-like growth factor 1 and dwarfism if the deficiency is prepubertal. Glaucoma - a disease of the eye characterized by increased intraocular pressure, excavation, and atrophy of the optic nerve; produces defects in the field of vision and eventual blindness. Glomerulonephritis - inflammation of the renal glomeruli that may not produce symptoms or may present with hematuria and proteinuria. Acute glomerulonephritis - an inflammatory disease of both kidneys predominantly affecting children from ages 2 to 12. Acute poststreptococcal glomerulonephritis (PSGN) - a kidney disease secondary to infection with Streptococci in which bacterial antigens complex with antibodies in the blood, deposit in the kidneys, and initiate an immune complex-mediated hypersensitivity reaction. Chronic glomerulonephritis - a slowly progressive glomerulonephritis most often associated with other systemic disease, including diabetes, malaria, hepatitis, or systemic lupus erythematosus, that generally leads to irreversible renal failure. Membranoproliferative glomerulonephritis (MPGN) - a chronic, slowly progressive glomerulonephritis in which the glomeruli are enlarged as a result of proliferation of mesangial cells and irregular thickening of the capillary walls, which narrows the capillary lumina. Membranous glomerulonephritis - a slowly progressive disease of unknown origin or that occurs secondary to autoimmune conditions, infections, specific drugs, or malignant tumors that is caused by immune complexes formed from the binding of antibodies to antigens of the glomerular basement membrane (GBM) or antigens transported from the systemic circulation and implanted in the GBM. Membranous nephropathy (membranous glomerulonephritis) - membranous nephropathy is caused by subepithelial deposition of antibodies (IgG4 subclass) to antigens (M-type phospholipase A2 receptor [PLA2R] protein) located on glomerular podocytes and activation of complement-mediated inflammation with injury and release of inflammatory mediators by mesangial and epithelial cells, resulting in increased membrane permeability, thickening of the glomerular membrane, and ultimately glomerular sclerosis. Mesangial proliferative glomerulonephritis - deposition of immune complexes in the mesangium with mesangial cell proliferation and expansion reducing blood flow and altering filtration membrane permeability with development of hematuria, proteinuria, hypertension, and uremia (nephritic syndrome); associated with IgA nephropathy, lupus nephritis, or early diabetic nephropathy. Rapidly progressive (crescentic) glomerulonephritis (RPGN) (subacute or extracapillary glomerulonephritis) - develops over days to weeks, primarily affects adults in their fifties and sixties, and may be idiopathic or associated with a proliferative glomerular disease (diffuse proliferation of extracapillary cells), such as lupus or poststreptococcal glomerulonephritis. Glucose-6-phosphate dehydrogenase (G6PD) deficiency - see Anemia. Gluten-sensitive enteropathy (celiac sprue) - a condition characterized by mucosal inflammation and villous atrophy in the gastrointestinal tract formed in response to a genetic predisposition for an immune response to gluten and similar proteins. Gonorrhea - a condition in which platelets aggregate within the kidney's small blood vessels, resulting in reduced blood flow to the kidney and subsequent kidney failure and destruction of the red blood cells; occurs usually after exposure to Shiga-like toxin from a strain of E. coli. Hemophilia A (classic hemophilia) - a genetic disorder in which a mutation in factor VIII causes prolonged clotting time, decreased formation of thromboplastin, and diminished conversion of prothrombin. Hemophilia B (Christmas disease) - a genetic disorder similar to hemophilia A in terms of symptoms but with a mutation in the factor IX gene. Hemophilia C (factor XI deficiency) - a genetic disorder characterized by a deficiency in factor XI, resulting in a mild form of hemophilia. Hemorrhagic stroke (spontaneous intracranial hemorrhage) - stroke usually caused by hypertension that results in bleeding in the brain and typically increases intracranial pressure and may lead to death. Henoch-Schönlein purpura nephritis - inflammation of the blood vessels causing bleeding into the skin, mucous membranes, internal organs, and other tissues; pain and inflammation in the joints; abdominal pain; gastrointestinal bleeding; inflammation of the kidneys; subcutaneous edema; encephalopathy; and inflammation of the testis. Heparin-induced thrombocytopenia (HIT) - see Thrombocytopenia. Hepatic encephalopathy - a condition that is usually caused by liver cirrhosis and portal hypertension in which toxins produced by the gut pass into the systemic circulation and damage brain cells, resulting in impaired cognition, tremor, and a decreased level of consciousness. Hepatitis B virus - one of six types of hepatitis virus that cause liver infection; it is most commonly sexually transmitted. Hepatocellular carcinoma (hepatocarcinoma; HCC) - primary carcinoma of the liver developing in hepatocytes. Hepatopulmonary syndrome - intrapulmonary vasodilation, intrapulmonary shunting, and hypoxia and portopulmonary hypertension (pulmonary vasoconstriction and vascular remodeling) are common respiratory complications of advanced liver disease and portal hypertension. Hepatorenal syndrome (HRS) - acute renal failure occurs because of a decrease in renal blood flow secondary to liver disease. Hereditary angioedema - an inherited, autosomal dominant disease characterized by episodic appearance of nonpitting edema, most often affecting the limbs, but capable of involving other parts of the body, including mucosal surfaces such as those of the intestine (causing abdominal pain) or respiratory tract (causing asphyxia); associated with deficiency of inhibitor of the first component of complement pathway (C1 esterase inhibitor). Hereditary hemochromatosis (HH) - autosomal recessive chronic liver disease caused by excessive intestinal absorption of elemental iron; characterized by elevated serum iron saturation, transferrin, and ferritin levels; improves with phlebotomy; increased risk of developing cirrhosis, liver cancer, and liver failure. Hereditary sideroblastic anemia - see Anemia. Hereditary spherocytosis - see Anemia. Hiatal hernia - an anatomic abnormality in which the esophageal hiatus is larger than normal, causing part of the stomach to protrude through the diaphragm and up into the esophagus or chest. High altitude cerebral edema (HACE) - an increase in severity of symptoms or signs of neurologic dysfunction, such as ataxia or altered consciousness, related to high altitude. High altitude pulmonary edema (HAPE) - a noncardiogenic pulmonary edema associated with pulmonary hypertension and elevated capillary pressure related to high altitude illness. Hirsutism - abnormal growth and distribution of androgen-sensitive hair growth on the face, body, and pubic area in a male pattern that occurs in women. Hodgkin lymphoma (HL) - see Lymphoma. Hormonal hyperplasia - growth of cellular layers chiefly in estrogen-dependent organs, such as the uterus and breast. After ovulation, for example, estrogen stimulates the endometrium to grow and thicken for reception of the fertilized ovum. Huntington disease (HD) - an autosomal dominant disease causing a progressive increase in involuntary, jerky, dyskinetic movements; mental deterioration; and premature death. Hyaline membrane disease (HMD) - a type of respiratory distress syndrome of the newborn in which there is formation of a hyaline-like membrane lining the terminal respiratory passages; extensive atelectasis is attributed to lack of surfactant. Hydrocele - a collection of fluid within the tunica vaginalis that is the most common cause of scrotal swelling. Hydrocephalus ex vacuo - hydrocephalus attributable to loss or atrophy of brain tissue; less commonly associated with raised intracranial pressure and dilation of the cerebral ventricles. Hydrops fetalis - edema formation in the fetal subcutaneous tissue because of an enzyme deficiency or any one of several other disorders. Hyperosmolar hyperglycemic nonketotic syndrome (HHNKS) - a complication seen in diabetes mellitus in which very marked hyperglycemia occurs, causing osmotic shifts in water in brain cells, and resulting in coma. It can be fatal or lead to permanent neurologic damage. Hypersensitive pneumonitis (extrinsic allergic alveolitis) - an allergic, inflammatory disease of the lungs caused by inhalation of organic particles or fumes. Hypertrophic cardiomyopathy - a genetic disorder caused by various mutations that thicken the heart muscle, possibly leading to obstruction of blood flow and heart dysfunction; this is a common cause of sudden death in young athletes. Hypogammaglobulinemia - see Immune deficiency. Hypoplastic anemia - see Anemia. Hypoplastic left heart syndrome (HLHS) - a condition in which the left side of the heart, including the aorta, aortic valve, left ventricle, and mitral valve, is underdeveloped and blood returning from the lungs flows through an opening in the atrial septum and the right ventricle pumps the blood into the pulmonary artery and then into the aorta. Hypospadias - a birth defect in which the urethral opening is abnormally placed, opening anywhere from the tip of the glans penis, to the shaft, or to the junction of the penis and scrotum or perineum in males; usually opens in the vagina in females. Hypotonia - forms of SCID characterized by an inability of lymphocytes and macrophages to present antigen because of defects in class I (MHC class I deficiency) or class II (MHC class II deficiency) MHC antigen expression. IL-7 receptor deficiency - a form of SCID resulting from mutations in the IL-7 receptor, which is necessary for maturation of T cells. JAK3 deficiency - a form of SCID resulting from mutations in JAK3, which encodes an enzyme (a tyrosine kinase) associated with the receptor for IL-2. Purine nucleoside phosphorylase (PNP) deficiency - a form of SCID resulting from a mutation in the enzyme PNP. RAG-1 and RAG-2 deficiencies - autosomal recessive mutations in recombination-activating gene (RAG-1 or RAG-2) enzymes that are necessary for genetic rearrangement of antibody and T-cell receptor variable regions. Reticular dysgenesis - the most severe form of SCID in which a common stem cell for all white blood cells is absent; therefore T cells, B cells, and phagocytic cells never develop. Wiskott-Aldrich syndrome (WAS) - an X-linked recessive trait resulting in chronic eczema with chronic suppurative otitis media, anemia, thrombocytopenic purpura, poor antibody response to polysaccharide antigens, and dysfunctions of cell-mediated immunity. X-linked SCID - a form of SCID with arrested maturation of T and natural killer (NK) cells and the production of immature B cells as a result of a defect in the IL-2 receptor gamma chain (IL-2R?), which is shared with many other cytokine receptors. Complement deficiency - a group of conditions in which specific proteins of the complement system are absent or suboptimal, resulting in diminished complement activity. These include: C1 deficiency - a deficiency of the first component of the classical pathway. C2 deficiency - a deficiency with an increased risk for recurrent respiratory tract infections with encapsulated bacteria and a systemic lupus erythematosus-like syndrome that may be complicated by kidney disease (glomerulonephritis). C3 deficiency - the most severe complement defect; an associated deficit of C3b, which is a major opsonin, results in a risk for recurrent life-threatening infections with encapsulated bacteria. C3 receptor deficiency - deficiencies in the complement receptor for C3 result in recurrent bacterial infections, particularly of the skin. C4 deficiency - results in an increased risk for recurrent respiratory tract infections with encapsulated bacteria and a systemic lupus erythematosus-like syndrome that may be complicated by kidney disease (glomerulonephritis). C9 deficiency - the most common terminal pathway defect and generally asymptomatic. Factor H deficiency - a deficiency of complement factor H resulting in increased destruction of C3 and a secondary C3 deficiency. Factor I deficiency - a deficiency of complement factor I resulting in increased destruction of C3 and a secondary C3 deficiency. Mannose-binding lectin (MBL) deficiency - a defect of the lectin pathway of complement activation resulting in an increased risk of infection with microorganisms that have polysaccharide capsules rich in mannose. Properdin deficiency - an X-linked defect in the alternative pathway of complement activation resulting in recurrent meningococcal infections. Phagocytic deficiency - a group of conditions in which phagocytes are diminished, resulting in increased bacterial infections. These include: Chediak-Higashi syndrome - a lethal, progressive, autosomal recessive, systemic disorder associated with oculocutaneous albinism, massive leukocyte inclusions (giant lysosomes), histiocytic infiltration of multiple body organs, development of pancytopenia, hepatosplenomegaly, and recurrent or persistent bacterial infections. Chronic granulomatous disease (CGD) - both X-linked and autosomal forms of mutations of the NADPH oxidase complex, resulting in diminished production of hydrogen peroxide and other oxygen products necessary for the bactericidal activity of myeloperoxidase. Cyclic neutropenia - an autosomal dominant mutation in the ELA2 gene resulting in periods of neutropenia lasting a few days to weeks. Severe congenital neutropenia - inadequate numbers of neutrophils resulting in a variety of recurrent and severe bacterial infections beginning early in life. Secondary immune deficiencies - Acquired immunodeficiency syndrome (AIDS) - an epidemic, transmissible retroviral disease caused by infection with the human immunodeficiency virus (HIV), resulting in destruction of T-helper cells, suppression of both antibody and cellular immune responses, and development of life-threatening infections with opportunistic organisms. Agranulocytosis - complete absence of granulocytes in the blood is usually secondary to arrested hematopoiesis in the bone marrow or massive cell destruction in the circulation. Qualitative leukocyte disorder - a group of conditions with various disruptions of leukocyte function. Quantitative leukocyte disorder - a group of conditions, frequently associated with infections and leukemias, with decreased production of leukocytes in the bone marrow or accelerated destruction of leukocytes in the circulation. Transient hypogammaglobulinemia of infancy - a period at 6 to 8 months when the newborn may not have produced adequate amounts of antibody to replace maternal antibody; in some infants this may lead to a period of increased susceptibility to infections. T-lymphocyte deficiency - a group of disorders in which T-cell development is defective, resulting in lower levels of cellular immunity. Diminished T-helper cell function may also decrease the production of antibody. These include: Chronic mucocutaneous candidiasis - a primary defect of T-lymphocyte response to a specific infectious agent, the yeast C. albicans. DiGeorge syndrome - a genetic disorder caused by deletion of a piece of chromosome 22 that results in cardiac defects, abnormal facies, thymic aplasia, cleft palate, and hypocalcemia. Immune thrombocytopenic purpura (ITP) - see Thrombocytopenia. Imperforate anus - a congenital defect in which the anal opening is absent because of the presence of a membranous septum or complete absence of the anal canal. Impetigo - Lactase deficiency - a condition in which insufficient lactase is present in the small intestine to digest lactose, resulting in lactose intolerance characterized by diarrhea, bloating, and gas in response to exposure to lactose. Lactose intolerance - a condition caused by lactase deficiency in which lactose is not metabolized, making it impossible for the small intestine to absorb it and causing excessive gas production and diarrhea when exposed to lactose-containing foods. Lambert-Eaton myasthenic syndrome - a generalized disorder of neuromuscular transmission caused by a defect in the release of acetylcholine from the presynaptic nerve terminals; often associated with small cell carcinoma of the lung, particularly in elderly men with a long history of cigarette smoking; weakness tends to affect solely axial muscles, girdle muscles, and less often the limb muscles; autonomic disturbances, dry mouth, and impotence are common; the deep tendon reflexes are unelicitable; caused by loss of voltage-sensitive calcium channels located on the presynaptic motor nerve terminal. Laryngomalacia - a congenital anomaly caused by a developmental delay in the laryngeal cartilage and supporting structures of the larynx that causes the cartilage to be floppy and fold in on itself during inspiration, producing high-pitched, coarse, and low-pitched sounds. Left heart failure (congestive heart failure) - inability of the left ventricle to maintain its circulatory load, with a corresponding rise in pressure in the pulmonary circulation usually with pulmonary congestion and ultimately pulmonary edema. Legg-Calvé-Perthes disease - blood supply to the head of the femur near the hip joint is interrupted, resulting in osteonecrosis of the corresponding epiphysis. Lennox-Gastaut syndrome - a generalized myoclonic epilepsy that occurs in children between 1 and 5 years of age as a result of various cerebral afflictions such as perinatal hypoxia, hemorrhage, encephalitis, and metabolic disorders of the brain; it is characterized by mental retardation, personality disorders, and generalized tonic seizures. Leukemia - a clonal malignant disorder of leukocytes in the bone marrow and usually, but not always of the blood; uncontrolled proliferation of malignant leukocytes, causing an overcrowding of bone marrow and decreased production and function of normal hematopoietic cells. Acute leukemia - characterized by undifferentiated or immature cells, usually a blast cell, and the onset of disease is abrupt and rapid. Acute lymphoblastic/lymphocytic leukemia (ALL) - excessive production and proliferation of malignant and immature white blood cells (lymphoblasts) in the bone marrow that progresses rapidly if left untreated. Acute myelogenous leukemia (AML) - excessive number of immature myeloid cells (myeloblasts) in the blood and bone marrow, overcrowding the marrow and decreasing the function of other cells. Chronic leukemia - Slow-growing cancer with many immature lymphocytes in the blood and bone marrow; the predominant cell is more differentiated but does not function normally. Chronic lymphocytic leukemia (CLL) - malignant transformation and progressive accumulation in the marrow of monoclonal B lymphocytes; rarely are CLL malignancies of T-cell origin. Chronic myelogenous leukemia (CML) - production of heterogeneous myeloid cells in the bone marrow, the majority of which express the Philadelphia chromosome; CML is considered a myeloproliferative disorder. Leukocytosis - a leukocyte count that is higher than normal. LH deficiency - a condition characterized by decreased or absent production of luteinizing hormone (LH), resulting in a decline in sex steroid production in testes/ovaries and associated infertility. Lichen planus - a recurrent rash of small, flat-topped bumps and rough scaly patches appearing on the skin, in the lining of the mouth, and in the vagina in response to inflammation or an allergy to a specific medication. Localized scleroderma (morphea) - rare and idiopathic sclerosis of the skin, usually with childhood onset. Locked-in syndrome - quadriplegia and mutism with intact consciousness and preservation of some eye movements; usually results from a vascular lesion of the anterior pons. Lupus erythematosus - any of a group of autoimmune connective tissue disorders that commonly produce red scaly lesions and are accompanied by fever, malaise, myalgia, fatigue, and weight loss. Discoid (cutaneous) lupus erythematosus (DLE) - lupus erythematosus limited to the skin; can progress to systemic lupus erythematosus (SLE). Systematic lupus erythematosus (SLE) - a chronic, multisystem, inflammatory disease; is one of the most common, complex, and serious of the autoimmune disorders. Lyme disease (borreliosis) - tick-borne spirochete bacterial infection that is characterized by a rash in the area of the bite, headache, neck stiffness, chills, fever, myalgia, arthralgia, malaise, fatigue, and possible development of arthritis in large joints. Lymphadenopathy - an alteration of lymphoid function characterized by enlarged lymph nodes. Lymphoblastic lymphoma (LL) - see Lymphoma. Lymphogranuloma venereum (LGV) - a sexually transmitted bacterial infection that enters the body through breaks in the skin or across the epithelial cell layer of mucous membranes and primarily targets the lymphatics and lymph nodes. Lymphoma - Diverse group of neoplasms arising from cell proliferation in lymphoid tissue. B-cell neoplasm - a group of lymphomas including myelomas that originate from B cells at various stages of differentiation; previously part of non-Hodgkin lymphoma. Burkitt lymphoma - an aggressive malignancy of the B lymphocytes characterized by a large osteolytic lesion in the facial bones and associated with Epstein-Barr virus infection. Hodgkin lymphoma (HL) - a neoplasm of lymphoid tissue that progresses from one group of lymph nodes to another; the lymph nodes, spleen, and liver become enlarged with the presence of Reed-Sternberg cells and is often accompanied by anemia, fever, and eventually death if not treated at an early stage; also referred to as Hodgkin disease. Lymphoblastic lymphoma (LL) - a progressive neoplasm arising in the thymus; most are of T-cell origin; a variant of acute lymphoblastic leukemia; common cause of non-Hodgkin lymphoma (NHL) in children. Lymphoplasmacytic lymphoma - also called Waldenström macroglobulinemia. Mucosa-associated lymphoid tissue (MALT) lymphoma - a low-grade B-cell lymphoma linked to infection with H. pylori. Mycosis fungoides - most common cutaneous T-cell lymphoma; present as focal or widespread erythematous patches or plaques, follicular papules, comedone-like lesions, and tumors. NK-cell neoplasm - Mesothelioma - a type of cancer that is usually associated with previous exposure to asbestos, which affects the pleura, the lining of the abdominal cavity, the pericardium, and most internal organ coverings. Metabolic acidosis - a condition in which the concentration of non-carbonic acids increases or bicarbonate (base) is lost from the extracellular fluid or cannot be regenerated by the kidney. Metabolic syndrome - a condition of unknown cause that presents with symptoms of insulin resistance, obesity, hypertension, dyslipidemia, and systemic inflammation. Metatarsus adductus - a foot deformity in which the front half of the foot bends inward, possibly because of the infant's position in the uterus. Methicillin-resistant Staphylococcus aureus (MRSA) - an infection that carries the extrachromosomal gene mecA for resistance to methicillin and has less sensitivity to inhibition by antibiotics. MHC class I deficiency - see Immune deficiency. MHC class II deficiency - see Immune deficiency. Microcephaly - a defect in which failure of normal brain growth causes delayed skull growth and production of a small head. Microcytic-hypochromic anemia - see Anemia. Microscopic colitis - a relatively common cause of diarrhea; occurs primarily in females and older adults. Migraine headache - a headache that usually begins in the temporal region unilaterally after vascular changes of cranial arteries and may cause irritability, nausea, vomiting, constipation or diarrhea, and photophobia. Mild concussion (mild traumatic brain injury) - temporary axonal disturbances without the loss of consciousness in response to a violent blow, jarring, shaking, or other closed-head injury. Miliaria - a skin disease caused by partially obstructed sweat glands that results in small and itchy rashes usually located in skinfolds and on areas of the body that may rub against clothing, such as the back, chest, and stomach. Minimal change nephropathy (MCN) - the foot processes of the renal capillary basement membrane are fused and deformed because of a T-cell disorder that reduces the anion component of the basement membrane and allows proteins to leak into the renal tubule. Minimally conscious state (MCS) - a condition in which a severely brain-damaged patient is capable of deliberate behavior distinguishable from unconscious reflexive actions. Mitral valve prolapse syndrome - the mitral valve cannot close properly because of one or both flaps being too large, possibly resulting in mitral valve regurgitation. Mixed precocious puberty - development of some secondary sex characteristics of the opposite sex (virilization of a girl or feminization of a boy); usually evident at birth and rare in older children. Molluscum contagiosum - a viral infection of the skin occurring in young children that affects the body, arms, and legs; it is spread through direct contact, saliva, or shared articles of clothing and is considered a sexually transmitted disease in adults, affecting the genitals, lower abdomen, buttocks, and inner thighs. Monoclonal gammopathy of undetermined significance (MGUS) - production of monoclonal antibodies by noncancerous plasma cells that accumulate in the blood. Motility diarrhea - diarrhea caused by excessive motility decreases transit time, mucosal surface contact, and fluid absorption secondary to resection of the small intestine (short bowel syndrome), surgical bypass of an area of the intestine, fistula formation between loops of intestine, irritable bowel syndrome- diarrhea predominant, diabetic neuropathy, hyperthyroidism, and laxative abuse. Moyamoya disease - an abnormality of the blood vessels that supply the frontal region of the brain in which vessels constrict or become completely occluded, resulting in diminished blood flow. The body attempts to compensate by growing new vessels at the base of the brain, which appear as a puff of smoke on angiography. Mucoepidermoid carcinoma - a tumor of the main or lobar bronchi lumen that may extend into the peribronchial tissue. Mucolipidosis (ML) - accumulation of both carbohydrates and lipids. Mucopolysaccharidosis - carbohydrate excess disorders. Mucopurulent cervicitis (MPC) - inflammation of the cervix with purulent endocervical exudate that may be asymptomatic or cause abnormal vaginal discharge and vaginal bleeding. Mucosa-associated lymphoid tissue (MALT) lymphoma - see Lymphoma. Multiple myeloma (MM) - most common and most aggressive plasma cell tumor; a clonal plasma cell cancer characterized by the slow proliferation of malignant cells as tumor cells form masses in the bone marrow that usually result in destruction of the bone; most secrete large amounts of monoclonal proteins that resemble intact immunoglobulins. Multiple organ dysfunction syndrome (MODS) - progressive disease often involving the ultimate failure of two or more organ systems after a severe illness or injury; disease process is initiated and perpetuated by uncontrolled systemic inflammatory and stress responses and is characterized by a hypermetabolic and hyperdynamic state that persists as organ dysfunction develops. Multiple papilloma (diffuse papillomatosis) - a minimum of five papillomas within a localized segment of breast tissue. Multiple sclerosis (MS) - chronic demyelinating disease of the central nervous system that causes inflammation and scarring of myelin sheaths. Muscular dystrophy - a general term for a number of hereditary, progressive degenerative disorders affecting skeletal muscles, and often other organ systems. Myasthenia gravis - neuromuscular disorder caused by an autoimmune response in which antibodies to acetylcholine receptors impair neuromuscular transmission. Mycosis fungoides - see Lymphoma. Myelodysplastic syndrome (MDS) - a group of hematologic conditions characterized by ineffective production of blood cells, resulting in anemia that requires chronic blood transfusion. Myoadenylate deaminase deficiency (MDD) - a genetic disorder in which an enzyme deficiency prevents the conversion of adenosine monophosphate (AMP) to inosine monophosphate, resulting in increased AMP loss and the inability to synthesize adenosine triphosphate for energy. Myocardial infarction - a heart condition of sudden onset in which muscle tissue dies because of a lack of blood flow, resulting in varying degrees of chest pain or discomfort, weakness, sweating, nausea and vomiting, and possibly loss of consciousness. excretion of more than 500?mL/day of urine concurrent with renal failure; although adequate volume of urine is excreted, renal tubules have impaired reabsorption and concentration and dilution function so that filtration is defective, resulting in accumulation of uremic toxins in the blood. Nonossifying fibroma (fibrous cortical deficit) - a benign fibrous tissue tumor forms in the metaphysis of any of the long bones but usually occurs in the thigh and shin bones in children and adolescents. Nonpuerperal hyperprolactinemia - the presence of excessive amounts of prolactin (the pituitary hormone that stimulates milk production) in the blood not related to pregnancy or childbirth; most common cause of galactorrhea. Nonsyndromic craniosynostosis (see Craniosynostosis) - the premature closure of one or more of the cranial sutures during the first 18 to 20 months of an infant's life, but an isolated defect unrelated to syndrome. Normocytic-normochromic anemia (NNA) - see Anemia. Obesity hypoventilation syndrome (pickwickian syndrome) - a condition of severely overweight individuals related to the inability to breathe rapidly or deeply enough to maintain adequate blood oxygen levels; characterized by obstructive sleep apnea, somnolence, hypoventilation, erythrocytosis, and heart failure. Obsessive-compulsive disorder (OCD) - an anxiety disorder characterized by obsessive thoughts and repetitive compulsive actions, such as cleaning, checking, or counting. Obstructive jaundice - jaundice related to extrahepatic or intrahepatic obstruction. Obstructive pulmonary disease - airway obstruction that is worse with expiration so that more force or more time is required to expire a given volume of air and emptying of the lungs is slowed; characterized by shortness of breath (dyspnea) and wheezing. Obstructive sleep apnea syndrome (OSAS) - a disorder of sleep characterized by airway obstruction and episodes of apnea accompanied by snoring. Obstructive uropathy - the blockage of urine flow, often by ureteral or kidney stones, resulting in the reflux of urine and subsequent injury to kidneys. Onychomycosis - a fungal infection of the fingernails or toenails that causes thickening, roughness, and splitting of the nails. Oophoritis - inflammation of the ovaries. Open pneumothorax (communicating pneumothorax) - see Pneumothorax. Optic glioma - tumor originating from glial cells in the brain that affects the optic nerve; commonly seen in children with neurofibromatosis. Organic brain syndrome - a constellation of physical brain disorders with psychologic or behavioral signs and symptoms and grouped according to symptoms rather than etiology. Orthopnea - shortness of breath (dyspnea) that occurs when an individual lies flat and is common in individuals with heart failure. Orthostatic (postural) hypotension - a sudden drop in blood pressure when a person assumes a standing position, resulting in dizziness, lightheadedness, blurred vision, and temporary loss of consciousness. Osmotic diarrhea - nonabsorbable substance in the intestine draws water into the lumen by osmosis, resulting in large-volume diarrhea; caused by drinking solutions with excessive sugars, salt, or vitamin C; maldigestion syndromes. Osteoarthritis (OA) - inflammatory degenerative joint disease in which synthesis and degradation of the articular cartilage in the movable joints are altered, resulting in wearing and destruction of cartilage. Osteochondrosis (Osgood-Schlatter disease) - a condition in children that results from the tendons pulling on the epiphysis of long bones, causing pain just below the knee, irritation and swelling, and possibly abnormal bone growth. Osteogenesis imperfecta (brittle bone disease) - a genetic disease in which collagen production is deficient, making the bones abnormally fragile and causing recurring fractures with only minimal trauma, deformity of long bones, a bluish coloration of the sclerae, and often the development of otosclerosis. Osteoid osteoma - a benign tumor in one of the bones of the lower extremities that is painful and is characterized by vascularized connective tissue and osteoid material that is surrounded by a large zone of thickened bone. Osteomalacia - a disease in which vitamin D or calcium deficiency or excessive renal phosphate loss causes a softening of the bones with accompanying pain and weakness. Osteomyelitis - a bacterial infection of the bone and bone marrow that occurs through open fractures, penetrating wounds, surgical operations, or by infiltration of the bloodstream; causes pain, high fever, and formation of an abscess at the site of infection. Osteoporosis - a disease in which the bones become porous and weakened, making bones easily fracture and slow to heal. Overactive bladder syndrome (OAB) - a chronic syndrome of overactivity of the detrusor muscle; characterized by urgency with involuntary detrusor contractions during the bladder filling phase. Oxygen toxicity - an iatrogenic inflammatory condition caused by prolonged exposure to high concentrations of supplemental oxygen resulting from damage to alveolocapillary membranes, disruption of surfactant production, and interstitial and alveolar edema; caused by oxygen free radicals. Paget disease of bone (PDB or osteitis deformans) - a bone disorder in which excessive bone remodeling causes enlarged, deformed bones that can weaken the bone integrity and result in bone pain, arthritis, deformities, or fractures. Painful bladder syndrome/interstitial cystitis (PBS/IC) (see Cystitis) - a condition occurring in women ages 20 to 40 years who have symptoms of cystitis, such as frequency, urgency, dysuria, and nocturia, for more than 6 weeks' duration; usually related to bacterial infection. Nonbacterial infectious cystitis - cystitis with negative urine cultures and no other known etiology; most common in immunocompromised individuals and related to viral, mycobacterial, chlamydial, or fungal infection. Noninfectious cystitis - cystitis without evidence of infection; usually autoimmune or related to exposure to radiation or chemotherapy treatment for pelvic or urogenital cancers. Panacinar emphysema - see Emphysema. Pancreatic insufficiency - a condition in which the pancreas does not secrete enough hormones and digestive enzymes for normal digestion to occur, resulting in malabsorption, malnutrition, vitamin deficiencies, and weight loss. Pancreatitis - inflammation of the pancreas, usually resulting in abdominal pain. Panhypopituitarism - a condition in which the secretion of all anterior pituitary hormones is inadequate or absent; caused by a variety of disorders that result in destruction or loss of function of all or most of the anterior pituitary gland. Pes planus (flatfoot) - a condition in which the arch of the foot never develops or it collapses and contacts the ground. Peyronie disease (bent nail syndrome) - a condition in which fibrous plaques grow in the soft tissue of the penis because of injury of the internal cavity of the penis that is accompanied by bleeding and scar tissue formation at the tunica albuginea of the corpora cavernosa. Phagocytic deficiency - see Immune deficiency. Phenylketonuria (PKU) - a genetic disorder in which the body lacks the enzyme necessary to metabolize the amino acid phenylalanine to tyrosine, resulting in accumulation of phenylalanine and subsequent brain damage and progressive mental retardation. Pheochromocytoma - a tumor of the adrenal medulla that causes the chromaffin cells to secrete increased amounts of epinephrine or norepinephrine. Phimosis - the foreskin of the penis of an uncircumcised male cannot be fully retracted. Pick disease - progressive atrophy of the cerebral convolutions in a limited area (lobe) of the brain, with clinical manifestations and course similar to those of Alzheimer disease. Pityriasis rosea - a skin disorder, thought to be caused by a virus, in which patches of ovular pink rash appear primarily on the trunk and extremities. Plaque psoriasis - see Psoriasis. Pneumoconiosis - a chronic disease of the lungs typically seen in miners, sandblasters, and metal grinders that is caused by repeated inhalation of dust particles, including iron oxides, silicates, and carbonates, that collect in the lungs and become sites for the formation of fibrous nodules that eventually replace lung tissue. Pneumonia - an infection of one or both lungs caused by a bacterium, virus, fungus, or other organism that enters the body through respiratory passages and causes high fever, chills, chest pain, difficulty breathing, cough with sputum, and possibly bluish skin from insufficiently oxygenated blood. Pneumothorax - the collapse of a lung and subsequent escape of air into the pleural cavity between the lung and the chest wall that is caused by trauma, environmental factors, or spontaneous occurrence and results in a sudden pain in the chest. Iatrogenic pneumothorax - the presence of air or gas in the pleural space caused by a rupture in the visceral pleura (which surrounds the lungs) or the parietal pleura and chest wall; is most commonly caused by transthoracic needle aspiration. Open pneumothorax (communicating pneumothorax) - spontaneous and traumatic pneumothorax in which air pressure in the pleural space equals barometric pressure because air that is drawn into the pleural space during inspiration (through the damaged chest wall and parietal pleura or through the lungs and damaged visceral pleura) is forced out during expiration. Primary (spontaneous) pneumothorax - occurs unexpectedly in healthy individuals (usually men) between ages 20 and 40 years; is most often caused by the spontaneous rupture of blebs on the visceral pleura. Secondary (traumatic) pneumothorax - spontaneous or secondary pneumothorax beginning with sudden pleural pain, tachypnea, and possibly mild dyspnea. Tension pneumothorax - the site of pleural rupture acts as a one-way valve, permitting air to enter on inspiration, but preventing its escape by closing during expiration and leading to air pressure in the pneumothorax exceeding barometric pressure. Polycystic ovary syndrome (PCOS) - a hormonal condition in which multiple ovarian cysts form because of elevated levels of androgens, resulting in hirsutism, obesity, menstrual abnormalities, infertility, and enlarged ovaries. Polycythemia vera - a chronic, progressive disease that is characterized by overgrowth of the bone marrow, excessive red blood cell production, and an enlarged spleen and causes headache, inability to concentrate, and pain in the fingers and toes. Pompe disease - see Acid maltase deficiency. Port-wine (nevus flammeus) stain - a birthmark caused by superficial and deep dilated capillaries in the skin that produce a reddish to purplish discoloration of the skin, usually on the face, but can occur anywhere on the body. Postconcussive syndrome - physical and personality changes that may occur after concussion of the brain, including amnesia, headache, dizziness, tinnitus, irritability, fatigability, sweating, heart palpitations, insomnia, and difficulty concentrating. Posthemorrhagic anemia - see Anemia. Postobstructive pulmonary edema (POPE) (negative pressure pulmonary edema) - a rare life-threatening complication that can occur after relief of upper airway obstruction (e.g., postextubation laryngospasm after anesthesia induction, epiglottitis, laryngeal tumor, or obstructive tonsils). Postrenal acute kidney injury - rare complication of urinary tract obstruction that affects the kidneys bilaterally (e.g., bilateral ureteral obstruction, bladder outlet obstruction-prostatic hypertrophy, tumors or neurogenic bladder, and urethral obstruction); obstruction causes an increase in intraluminal pressure upstream from the site of obstruction. Postthrombotic syndrome (PTS) - a syndrome that follows a vascular thrombosis, such as persistent edema. Posttraumatic stress disorder (PTSD) - a psychologic disorder that may develop in individuals who have experienced or witnessed traumatic events; is characterized by recurrent flashbacks of the traumatic event, nightmares, irritability, anxiety, fatigue, forgetfulness, and social withdrawal. Potter syndrome - a syndrome of renal agenesis with hypoplastic lungs and associated neonatal respiratory distress, hemodynamic instability, acidosis, cyanosis, edema, and characteristic (Potter) facies; death usually occurs from respiratory insufficiency, which develops before uremia. Poverty of content - a disorder, also called poverty of speech content, that is characterized by disorganized speech that conveys little information and may be vague or contain repetitive or obscure phrases. Prader-Willi syndrome - a rare genetic disorder caused by gene deletions on paternal chromosome 15 that result in short stature, hypotonia, small hands and feet, obesity, mild to moderate mental retardation, and hypogonadism. Precocious puberty - a condition in which a boy or girl undergoes the changes associated with puberty at an unexpectedly early age; often caused by a pathologic process that increases the secretion of estrogens or androgens. Premenstrual dysphoric disorder (PMDD) - recurrence in the luteal phase of the menstrual cycle of distressing physical, psychologic, or behavioral changes that impair interpersonal relationships or interfere with usual activities. Premenstrual syndrome (PMS) - a group of symptoms that occur in many women from 2 to 14 days before menstruation begins, including abdominal bloating, breast tenderness, headache, fatigue, irritability, depression, and emotional distress. Protein S deficiency - a disorder characterized by a lack of anticoagulant activity and an increased tendency to form blood clots because of decreased degradation of factor Va and factor VIIIa. Pseudothrombocytopenia - see Thrombocytopenia. Psoriasis - a noncontagious autoimmune skin disorder in which the skin becomes scaly and inflamed when cells in the outer layer of skin reproduce faster than normal and accumulate as plaques on the skin surface. Erythrodermic (exfoliative) psoriasis - widespread red, scaling lesions that cover a large body surface area; often accompanied by itching or pain associated with constitutional symptoms (fever, chills, fatigue) and skin infections. Guttate psoriasis - sudden appearance of small papules on the trunk and extremities, occasionally after a streptococcal respiratory tract infection in children. Inverse psoriasis - rare development of large, smooth, dry, and deep red lesions in skinfolds (i.e., axilla or groin). Plaque psoriasis - most common form of psoriasis; begins with well-demarcated, thick, silvery, scaly erythematosus inflammatory lesions with epidermal hyperproliferation and the presence of activated T lymphocytes that may become mild, moderate, or severe, depending on the size, distribution, and inflammation of the lesions. Pustular psoriasis - blisters of noninfectious pus that develop over areas of plaque psoriasis. Pulmonary artery hypertension (PAH) - increased blood pressure in the pulmonary artery attributable to vasoconstriction that may eventually lead to fibrosis, increased workload, hypertrophy of the right ventricle, and right heart failure; etiology may be idiopathic, familial, or associated with other diseases. Pulmonary embolism (PE) - dislodgement of a blood clot from its site of origin and embolization to the arterial blood supply of one of the lungs, resulting in shortness of breath and difficulty breathing, rapid breathing that is painful, cough, and (in severe cases) hypotension, shock, loss of consciousness, and death. Pulmonary stenosis - a condition in which the opening into the pulmonary artery from the right ventricle narrows. Pure red cell aplasia (PRCA) - an acquired or congenital condition in which the bone marrow lacks red blood cell precursors even though megakaryocytes and white blood cell precursors are usually present at normal levels. Purine nucleoside phosphorylase (PNP) deficiency - see Immune deficiency. Pustular psoriasis - see Psoriasis. Pyloric stenosis - a congenital abnormality in which the pylorus is narrow, resulting in poor feeding, weight loss, and progressively worsening vomiting. Pyramidal/spastic cerebral palsy - palsy resulting from damage or defects in the brain's corticospinal pathways (upper motor neuron) in either one or both hemispheres. Qualitative leukocyte disorder - see Immune deficiency. Quantitative leukocyte disorder - see Immune deficiency. RAG-1/RAG-2 deficiencies - see Immune deficiency. Rapidly progressive (crescentic) glomerulonephritis (RPGN) - see Glomerulonephritis. Raynaud disease - a condition in which the blood vessels spasm because of inadequate blood supply, resulting in discoloration of the fingers and/or toes after exposure to changes in temperature or emotional events. Raynaud phenomenon - a condition caused by the temperature-dependent deposition of immune complexes in the capillary beds of the peripheral circulation, which blocks the circulation and causes localized pallor and numbness, followed by cyanosis and eventually gangrene if the circulation is not restored. Rectocele - a condition caused by childbirth or hysterectomy in which the region between the rectum and vagina bulges toward the vagina, resulting in a sense of pressure or protrusion within the vagina, the feeling of incomplete emptying of the rectum, difficulty passing stool, discomfort or pain during evacuation or intercourse, constipation, vaginal bleeding, fecal incontinence, prolapse of the bulge through the opening of the vagina, or rectal prolapse through the anus. Refeeding syndrome - metabolic disturbances that occur upon initiating parenteral or enteral nutritional therapy to individuals who are severely malnourished; starvation results in movement of phosphate, magnesium, and potassium ions out of the cells and into the plasma and refeeding increases insulin levels and stimulates movement of glucose and these ions back into the cells, resulting in dangerously low levels in the plasma (hypophosphatemia, hypomagnesemia, hypokalemia, hyponatremia, hypocalcemia, and vitamin deficiency) and other potentially fatal metabolic complications. Relative polycythemia - a relative increase in the number of red blood cells caused by loss of the fluid portion of the blood. Renal agenesis - only one functional kidney is present at birth. Renal calculi (nephrolithiasis) - also called urinary stones (urolithiasis); masses of crystals, protein, or other substances that can be located in the kidneys, ureters, and urinary bladder and are a common cause of urinary tract obstruction in adults. Renal cell carcinoma (RCC) - the most common renal neoplasm (approximately 80% of all renal neoplasms). Renal dysplasia - abnormal tissue development in one or both kidneys. Respiratory acidosis - occurs when there is alveolar hypoventilation. Carbon dioxide is retained, increasing [H+] (as H2CO3), thus decreasing the ratio of to PCO2 and producing acidosis. Respiratory alkalosis - occurs when there is alveolar hyperventilation and decreased concentration of plasma carbon dioxide (termed hypocapnia), thus increasing the ratio of to PCO2 (H2CO3). Respiratory distress syndrome (RDS) of the newborn - a condition, also known as hyaline membrane disease (HMD), that is a type of respiratory distress in newborns, most often in prematurely born infants, those born by cesarean section, or those having a diabetic mother; the immature lungs do not produce enough surfactant to retain air so the air spaces empty completely and collapse after exhalation. Reticular dysgenesis - see Immune deficiency. Retinoblastoma - an autosomal dominant or sporadic disorder in which a malignant tumor forms in the retina of one or both eyes; typically found in infants. Reversible sideroblastic anemia - see Anemia. Rhabdomyolysis - Secondary amenorrhea - menstruation begins at puberty but then is subsequently suppressed for three or more cycles or for 6 months in women who previously menstruated. Secondary dysmenorrhea - altered menstruation because of inflammation, infection, tumor, or anatomic factors. Secondary generalization - the process by which a simple partial seizure involving one hemisphere becomes a generalized seizure involving the second hemisphere. Secondary hyperparathyroidism - a condition of elevated levels of parathyroid hormone resulting from disease such as renal failure in which parathyroid hormone concentration is elevated in response to vitamin D deficiency. Secondary hypertension - a condition of elevated blood pressure that is associated with other conditions, primarily with renal disease by a renin-dependent mechanism or a fluid volume-dependent mechanism. Secondary hypothermia - depressed body temperature as a consequence of a serious systemic disorder, for example, endocrine disorders. Secondary (acquired) immune deficiency - see Immune deficiency. Secondary MODS - the result of an excessive inflammatory reaction, after a latent period following the initial injury, in organs distant from the site of the original injury. It is postulated that the resulting organ trauma is caused by the host response to a second insult rather than being a direct result of the primary injury. Secondary (traumatic) pneumothorax - see Pneumothorax. Secondary septic arthritis - a bacterial infection in the joints, causing them to become inflamed and the bacteria to proliferate. Secondary syphilis - the most contagious stage of syphilis infection; characterized by a skin rash that appears on the trunk and extremities 1 to 6 months after the primary infection and possibly mucous patches on the genitals or inside the mouth. Selective IgA deficiency - see Immune deficiency. Sepsis - severe physiologic stress typically caused by an infection; its complications result from activation of biochemical and physiologic cascades that lead to the formation or activation of cytokines and other mediators that produce vasodilation, increased capillary permeability, maldistribution of blood flow, and cardiovascular and cellular dysfunction. Septic shock - a condition caused by systemic infection that results in decreased tissue perfusion and oxygenation and can lead to multiple organ dysfunction syndrome and death. Serum sickness - a form of hypersensitivity caused by injection of soluble antigen such as antiserum, which activates a type III hypersensitivity response (formation of soluble circulating antigen-antibody [IgG or IgM] complexes) that activates the complement system. Severe combined immune deficiency (SCID) - see Immune deficiency. Severe congenital neutropenia - see Immune deficiency. Shock - a condition in which the circulatory system is unable to provide adequate circulation to the body tissues because of inadequate pumping by the heart, a reduction in blood volume, or a reduction in blood pressure; it results in slowing of vital functions and possibly death. Short bowel syndrome - a group of malabsorption conditions resulting from massive resection of the small bowel, the degree and kind of malabsorption depending on the site and extent of the resection; it is characterized by diarrhea, steatorrhea, and malnutrition. Sickle cell anemia - see Anemia. Sickle cell disease (SCD) - see Anemia. Sickle cell-Hb C disease - see Anemia. Sickle cell-thalassemia disease - see Anemia. Sickle cell trait - see Anemia. Sideroblastic anemia (SA) - see Anemia. Silicosis - inflammation of the lung resulting from the inhalation of free silica (silicon dioxide) and silica-containing compounds, which occurs in mining and related industries. Simple febrile seizure - benign and most common form of childhood seizure. Simple fibroadenoma - benign solid tumors composed of both fibrous and glandular tissue. Sliding hiatal hernia - the most common type of hernia, occurring when the proximal portion of the stomach moves into the thoracic cavity through the esophageal hiatus, an opening in the diaphragm for the esophagus and vagus nerves. Small cell lung carcinoma (SCLS) - the most common type of neuroendocrine lung tumor; mostly arise from the central part of the lung. Smallpox (variola) - an infectious viral disease that is caused by a poxvirus and result in high fever, aches, and widespread eruption of large sores that leave scars. Smoldering myeloma - a condition in which abnormal plasma cells produce a monoclonal protein, but no symptoms or complications of myeloma are present and may not be present for several years. Solitary plasmacytoma - a solitary tumor of malignant plasma cells that may result in a single lytic bone lesion or may be in the tissues (extramedullary plasmacytoma). Spina bifida occulta - the mildest form of congenital disorder of incomplete closure of the embryonic neural tube; the outer part of some vertebrae may not be completely closed, but the defect is not apparent to the unaided eye and usually causes no serious neurologic dysfunctions. Spinal stenosis - narrowing of the spinal canal as a result of congenital anomaly or spinal degeneration, resulting in pain, paresthesias, and neurogenic claudication. Spondylolisthesis - forward displacement of one of the lower lumbar vertebrae over the vertebra below it or over the sacrum. Sprain - a ligament tear, which occurs most commonly in the wrist, ankle, elbow, and knee joints. Squamous cell carcinoma (SCC) - a tumor of the epidermis and the second most common human cancer. a fatal autosomal recessive lysosomal storage disorder in which the lysosomal enzyme hexosaminidase A (HexA) is deficient, leading to accumulation of gangliosides in the brain and nerve tissue, mental retardation, convulsions, blindness, and premature death. T-cell neoplasm - see Lymphoma. Tension pneumothorax - see Pneumothorax. Tertiary syphilis - the most severe stage of syphilis, which can begin as early as 1 year after the initial infection but can take up to 10 years to manifest and is characterized by gummas-soft, tumor-like growths found in the skin and mucous membranes and often in the skeleton-joint deformity, neurosyphilis, and cardiovascular syphilis. Tethered cord syndrome - a group of neurologic disorders related to malformation of the spinal cord in which the cord becomes abnormally attached or tethered as a result of scar tissue that develops as the cord transcends the vertebral canal with growth; tethering may decrease blood flow. Tetralogy of Fallot - a congenital condition that is characterized by four malformations including ventricular septal defect, misplacement of the origin of the aorta, narrowing of the pulmonary artery, and enlargement of the right ventricle. Thalassemia - see Anemia. Thromboangiitis obliterans (Buerger disease) - inflammation of the medium-sized arteries and veins because of thrombotic occlusion, resulting in ischemia and gangrene. Thrombocythemia - a chronic disorder of sustained megakaryocyte proliferation that increases the number of circulating platelets and results in megakaryocytic hyperplasia, splenomegaly, and complications by hemorrhagic and thrombotic episodes. Thrombocytopenia - a reduced number of circulating platelets. Acute idiopathic thrombotic thrombocytopenic purpura - a form of thrombocytopenic purpura (TTP) characterized by thrombotic microangiopathy in which platelets aggregate and cause occlusion of arterioles and capillaries within the microcirculation, leading to increased platelet consumption and organ ischemia. Autoimmune neonatal thrombocytopenia - destruction of platelets in a fetus/neonate by antiplatelet antibodies produced in the mother against her own platelet antigens (autoimmune) that are shared with the child, and the antibodies are transported across the placenta and destroy the child's platelets. Chronic relapsing thrombotic thrombocytopenic purpura - a rare familial form of TTP characterized by recurring episodes of thrombocytopenia; usually seen in children. Heparin-induced thrombocytopenia (HIT) - a form of drug-induced thrombocytopenia caused by IgG antibodies against the heparin- platelet factor 4 complex leading to platelet activation and thrombocytopenia. Idiopathic thrombocytopenic purpura (ITP) (autoimmune or primary thrombocytopenic purpura) - the most common cause of thrombocytopenia, secondary to increased immune-mediated platelet destruction; can be acute or chronic. Immune thrombocytopenic purpura (ITP) - a condition in which the number of platelets in the blood is reduced by the production of antibodies against platelets, resulting in ecchymoses and hemorrhage from mucous membranes, anemia, and extreme weakness. Neonatal alloimmune thrombocytopenic purpura (NATP) - a condition in which fetal platelets have an antigen from the father that is absent in the mother, and the mother forms antibodies that cross the placenta and destroy the fetal platelets. Pseudothrombocytopenia - an artificially low platelet count in anticoagulated blood caused by cooling of the blood and autoagglutination of platelets. Thrombotic thrombocytopenic purpura (TTP) - altered blood coagulation caused by an enzymatic deficiency that is characterized by a reduced number of platelets in the blood, the formation of blood clots in tissue arterioles and capillaries, and neurologic damage. Thrombophilia - genetic or acquired abnormality of the coagulation system with an increased risk for thrombosis. Thrombotic thrombocytopenic purpura (TTP) - see Thrombocytopenia. Thrush - a yeast infection of the mouth and throat that presents as creamy white curdlike patches on the tongue, inside the mouth, and on the back of the throat and that is commonly associated with yeast infection of the esophagus. Thyrotoxicosis - excessive concentrations of thyroid hormones in the body that are marked by increased metabolic rate, heat intolerance, goiter, reproductive disorders, excessive sweating, and other alterations in systemic function. Tinea capitis - fungal infections of the skin classified according to their location on the body. Tinea corporis (ringworm) - a fungal infection of the scalp; much more common in children than in adults. Tinea infection - one of a group of fungal skin infections that include athlete's foot, folliculitis, jock itch, ringworm, and pityriasis versicolor. Tinea pedis - chronic, superficial fungal infection of the skin of the foot common in adults. Tinea unguium - a fungal infection of the nails. Tinnitus - a condition in which the person hears ringing, buzzing, or other sounds without an external cause. T-lymphocyte deficiency - see Immune deficiency. Tophaceous gout - a form of purine metabolism disorder characterized by formation of chalky deposits of sodium biurate under the skin and in the joints. Toxic epidermal necrolysis (TEN) - a rare adverse reaction to certain drugs in which a large portion of the skin becomes intensely red, may develop blisters, and exfoliates. Toxoplasmosis - a protazoan infection that is the most common opportunistic infection and occurs in one-third of persons with HIV. Tracheomalacia (tracheobronchomalacia) - a congenital or acquired condition characterized by weakness of the tracheal support cartilage, resulting in tracheal collapse when increased airflow is needed. Trachoma (granular conjunctivitis or Egyptian ophthalmia) - a contagious, chronic inflammation of the mucous membranes of the eyes, caused by Chlamydia trachomatis. Transcortical dysphasia (transcortical sensory dysphasia, mixed transcortical dysphasia, isolated speech center) - Ureterohydronephrosis - dilation of both the ureter and the pelvicaliceal system. Ureteropelvic junction (UPJ) obstruction - an impediment to the drainage of urine from the kidney, usually attributable to partial or intermittent blockage of the renal collecting system at the junction of the renal pelvis and ureter. Urethral atresia - congenital absence or closure of a normal body opening or tubular structure; congenital imperforation of the urethra. Urothelial (transitional cell) carcinoma - the most common bladder malignancy, appearing on the inner lining of the bladder. Urticaria - hives; a dermal (skin) manifestation of type I allergic reactions. Usual ductal hyperplasia (UDH) - description of normal hyperplasia of cells that line the ducts in the normal breast; additional layers of benign cells are present, but with normal cellular structure and arrangement. Uterine prolapse - descent or herniation of the uterus into or beyond the vagina because of weakness of the pelvic musculature, ligaments, and fascia or obstetric trauma and lacerations sustained during labor and delivery. Vacuolar myelopathy - HIV-induced loss of myelin and spongy degeneration of the spinal cord that may cause spastic paraparesis, sensory ataxia in lower limbs, and unsteady gait. Vaginismus - a form of sexual dysfunction that is caused by a psychologic disorder or vaginal inflammation in which the muscles at the entrance to vagina contract and prevent sexual intercourse. Vaginitis - infection of the vagina usually caused by a fungus that may cause itching or burning and a discharge. Vaginosis - vaginal irritation without white blood cells or other indication of infection. Varicocele - a painful condition in which the veins in the scrotum that develop in the spermatic cord enlarge, and if the valves that regulate blood flow from these veins become dysfunctional, blood does not leave the testis, thereby causing swelling in the veins above and behind the testis. Varicose bronchiectasis - a condition in which the bronchi become large and balloon-like. Venous angioma - abnormal veins, usually near the ventricular wall, that form as a congenital anomaly. Venous stasis ulcer - a condition affecting the lower leg in which leaky valves, obstructions, or regurgitation in veins impairs blood flow back to the heart, resulting in pooling of blood in the lower leg and subsequent tissue damage. Ventricular septal defect (VSD) - a congenital malformation in which the wall between the left and right ventricles has a hole that allows blood to travel between the left and right ventricles, potentially leading to congestive heart failure. Vesicoureteral reflux (VUR) - reflux of urine from the bladder into the ureter. Vestibular nystagmus - involuntary rapid movement of the eyeball that is due to disturbance of the vestibular system; eye movements are rhythmic, with slow and fast components. Vitiligo - an autoimmune-related loss of melanocytes resulting in the depigmentation of patches of skin. von Willebrand disease - an inherited disease in which the von Willebrand factor proteins that are made in the blood vessel walls and function to control platelet activity are abnormal or absent, resulting in a tendency to hemorrhage. Vulvodynia - also referred to as vulvitis, vestibulitis, or vulvovestibulitis; chronic pain and inflammation of the vulva or vestibule, or both. Waldenström macroglobulinemia - see Lymphoma. Wallerian degeneration - the degeneration of a nerve fiber that has been separated from its nutritive center by injury or disease; characterized by segmentation of the myelin and resulting in atrophy and destruction of the axon. Warm autoimmune hemolytic anemia - see Anemia. Wilms tumor - see Nephroblastoma. Wilson disease - a genetic disease in which the ability to metabolize copper is impaired, resulting in an accumulation of copper deposits in organs such as the brain, liver, and kidneys and subsequent organ dysfunction and failure. Wiskott-Aldrich syndrome (WAS) - see Immune deficiency. Xanthelasma - a planar xanthoma involving the eyelid(s). X-linked hyper-IgM syndrome - see Immune deficiency. X-linked SCID - see Immune deficiency. Zika virus - a single-stranded RNA virus from the Flaviviridae family, genus Flavivirus, that is predominantly transmitted through bites from infected mosquitos; infection during pregnancy has been associated with severe fetal infection and associated CNS abnormalities. Zollinger-Ellison syndrome - the association of atypical, intractable, sometimes fulminating peptic ulcers with extreme gastric hyperacidity and benign or malignant gastrinomas in the pancreas.