Ver el código de «Eponyms (F-L)»

==F==

===Fabricius, bursa of===
In birds, thymus-like gland that is an outgrowth of the cloaca and site for B cell maturation. 

===Fabry's disease===
X-linked recessive sphingolipidosis (sulfatidose) alpha-galactosidase deficiency resulting in increased globosides, reddish-purple skin rash, kidney and heart failure, peripheral neuropathy, pain in lower extremities (acroparesthesias). Accounts for 1:117,000 live births; most common clinical features are telangiectases and corneal dystrophy; can be treated with biweekly infusions of recombinant human alpha-galactosidase A. 

===factor V Leiden===
Arg(506)-&gt;Gln mutation, results in resistance to cleavage by activated protein C (an anticoagulant) leading to hypercoagulability. Found in 20% of patients with venous thromboembolism, 6% of U.S. population. 

===Fahr's disease===
Neurodegenerative syndrome associated with symmetric intracerebral calcifications in basal ganglia, associated with cognitive and movement disorders including spastic paralysis, athetosis. 

===Fallot, tetralogy of===
1. ventricular septal defect; 2. infundibular, valvar, or supravalvar pulmonic stenosis; 3. an anteriorly displaced aorta that receives blood from both ventricles; 4. right ventricular hypertrophy. 

===Fathergi’s Sign===
*Abdomen more tender with sitting up
*Associated with muscle strain

===Fanconi-Bickel syndrome===
Type XI glycogen storage disease, hepatic glycogenosis with renal Fanconi syndrome; caused by defect in GLUT-2 transporter. Characterized by proximal renal tubular dysfunction, impaired glucose and galactose utilization, liver and kidney glycogen accumulation. Presents as failure to thrive in first year with hepatomegaly and kidney enlargement. 

===Fanconi's anemia===
Autosomal recessive disorder characterized by progressive bone marrow failure at age 5-7, congenital malformations (frequently defects in thumbs or forearms, kidneys, GI, skin); 20% develop cancer (primarily AML but also in skin, GI, GU). Can be diagnosed by increased sensitivity of FA cells to bifunctional alkylating agents (e.g. diepoxybutane or mitomycin C). 

===Fanconi's syndrome===
Generalized dysfunction of proximal renal tubule leading to glycosuria, hyperphosphaturia, hypophasphatemia, aminoaciduria, and systemic acidosis; may be associated with outdated tetracyclines. 

===Farber's disease===
A lysosomal storage disease or sphingolipidosis from ceraminidase deficiency leading to painful and progressively deformed joints, subcutaneous nodules, granulomas, fatal in early life. 

===farmer's lung===
Hypersensitivity pneumonitis from exposure to antigens of microorganisms which colonize equipment used in farming, including from moldy hay, grain, silage (e.g. thermophilic actinomycetes, fungus such as Aspergillus umbrosus). 

===farmer's skin===
Cutis rhomboidalis nuchae. 

===Fay sign===
In carotid arteritis, pressure along the carotid causing pain to spread in distal branches of external carotid to jaw, ear, and temple. 

===Fechtner syndrome===
Alport's syndrome with leukocyte inclusions and macrothrombocytopenia; associated with mutations in nonmuscle myosin heavy chain-9. 

===Felty's syndrome===
Rheumatoid arthritis, splenomegaly, and neutropenia, and also leg ulcers; associated with HLA-DR4. 

===Ferguson's reflex===
Stimulation of the cervix leading to contraction of the uterus through oxytocin release. 

===fetor hepaticus===
"Musty" or "sweet odor" from the formation of mercaptans by the action of GI bacteria on the sulfur-containing amino acid methionine and shunting of splanchnic blood from the portal into the system circulation (portosystemic shunting). 

===fifth disease===
Erythema infectiosum, associated with parvovirus B19 infection, characterized by "slapped cheeks" and erythematous lacy eruption on the trunk and extremities. 

===Filatov-Dukes's disease===
Fourth disease, historically felt to be a separate form of rubella and then felt to be a non-entity but perhaps now is Staph scarlet fever Lancet 357:299 (2001); alternatively misdiagnosed cases of rubella or scarlet fever. 

===Finkelstein's test===
In de Quervain's tenosynovitis, dorsal thumb pain when the wrist is deviated in an ulnar fashion and the thumb is flexed across the palm. 

===first disease===
Measles, also known as rubeola, caused by paramyxovirus, described in 1627. 

===Fisher grading scale===
Grading system for subarachnoid hemorrhage. Grade 1, no bleed; grade 2, &lt;1 mm thick; grade 3 localized clot and/or layer &gt;1 mm, high risk of vasospasm; grade 4, any thickness with intraventricular hemorrhage or parenchymal extension 

===Fisher's syndrome===
See Miller Fisher syndrome. 

===Fitzgerald factor===
High molecular weight kininogen; in intrinsic phase of coagulation, part of complex between factor XII, prekallikrein, and subendothelial collagen; facilitates conversion of XII to XIIa. Deficiency not associated with bleeding. 

===Fitz-Hugh-Curtis syndrome===
Associated with spread of gonococci or chlamydia: perihepatitis manifested by right upper quadrant or bilateral upper abdominal pain, tenderness, and occasionally by a hepatic friction rib. 

===Flatbush diabetes===
GAD antibody negative diabetes in adult black patients with diabetic ketoacidosis and increased frequency of human leukocyte antigen DR3 and DR4. 

===Fletcher factor===
Prekallikrein. In intrinsic phase of coagulation, converts XII to XIIa. Deficiency results in elevated PTT but with no clinical bleeding . 

===Foix-Alajouanine disease===
Angiodysgenetic necrotizing myelopathy, venous angiomatous malformation of the spinal cord and overlying meninges associated with ischemic damage and worsening neurologic symptoms in lumbosacral cord. 

===Foley catheter===
A catheter with a balloon at the tip; inflated balloon aids in retention of catheter in e.g. bladder. Developed by Frederic Foley (1891-1966) in the 1930s. 

===Følling's disease===
Phenylketonuria. Følling, a Norwegian physician who described PKU in 1934. 

===Fontan procedure===
For treating tricuspid atresia, pulmonary atresia, or hypoplastic left heart syndrome, procedure developed in 1968 whereby IVC is connected to pulmonary artery; long term complications include arrhythmias and protein losing enteropathy because of edema in liver and small bowel. 

===Forbes disease===
Glycogen storage disease type III; see Cori's disease. 

===Forbes-Albright syndrome===
Galactorrhea-amenorrhea caused by a pituitary adenoma. 

===Fordyce's spots===
Ectopic sebaceous glands seen in healthy mouth; may be confused with Koplik's spots which has an erythematous halo by comparison. 

===Forrester classification===
In myocardial infarction, class I, PWP&lt;18 and CI&gt;2.2 L/min/m2, 2% mortality; class II, PWP&gt;18 and CI&gt;2.2, 10% mortality; class III, CI&lt;2.2 and PWP&lt;18, 12% mortality; class IV, PWP&gt;18 and CI&lt;2.2, 54% mortality. 

===Forscheimer spots===
In 20% of rubella, small, red macules on the soft palate that may later expand and coalesce; not pathognomonic since they may also appear in scarlet fever, roseola, mono. 

===Forsmann antibodies===
Antibody that may be found in normal individuals and can cause false positive heterophile antibody test; guinea pig kidney cells contain Forsmann antigens; see Paul-Bunnell-Davidsohn test. 

===Foster Kennedy syndrome===
Optic atrophy, contralateral papilledema, and anosmia; may be associated with olfactory groove meningioma. Described by Robert Foster Kennedy, though first described by Gowers. 

===Fothergill's sign===
In rectus sheath hematomas, tender mass that does not cross the midline and remains palpable when patient tenses the rectus muscle (bluish discoloration not usually seen until 3 or 4 days). 

===Fournier's gangrene===
Necrotizing infection of the perineal and genital fascia. 

===fourth disease===
Filatov-Dukes's disease, also known as Staphylococcal scarlet fever, caused by Staph. aureus epidermolytic toxin, described in 1900. 

===Foville's syndrome===
Dorsal pontine injury giving rise to lateral gaze palsy, ipsilateral facial palsy, contralateral hemiparesis. 

===Fowler's syndrome===
Idiopathic voiding dysfunction and urinary retention. 

===Fox-Fordyce disease===
Chronic, pruritic, papular eruption occurring in areas with apocrine glands, affecting mainly women. 

===Fox's sign===
In hemorrhagic pancreatitis, ecchymosis of the inguinal ligament due to blood tracking from the retroperitoneum and collecting at the inguinal ligament. 

===Fränkel's sign===
In scurvy, dense zone of provisional calcification at the margins of the growth plate (white line); see also Trummerfeld zone. 

===Franklin's disease===
Gamma heavy chain disease, a rare B cell lymphoproliferative disease characterized by lymphadenopathy, fever, anemia, malaise, hepatosplenomegaly, and weakness, most distinctive symptom palatal edema. 

===Frank's sign===
Earlobe crease, associated with coronary artery disease (N Engl J Med. 1973;289:327-8). 

===Frasier syndrome===
Female external genitalia in 46 XY patients, late renal failure, streak gonads, and high risk of gonadoblastoma; associated with mutation in WT1 gene. 

===Fregoli syndrome===
Delusionalbelief that a single person can assume the identity of different people through disguise; after Italian actor Fregoli; see also Capgras syndrome. 

===Freiberg disease===
Osteochondrosis of second metatarsal head; associated with avascular necrosis of metatarsal head; most patients are female. 

===Frey syndrome===
Gustatory sweating or auriculotemporal syndrome seen in the context of parotid surgery; ipsilateral forehead becoming drenched with sweat. Attributed to aberrant neuronal regeneration resulting in parasympathetic cholinergic innervation of cutaneous sympathetic receptors. 

===Friedman curve===
Graph of dilatation of cervix v. fetal descent during active labor. 

===Friedreich's ataxia===
A spinocerebellar degeneration, autosomal recessive form manifesting at around 11 years, less common autosomal dominant form around 20 years. Initial symptoms: gait ataxia, hand clumsiness, dysarthria, deep tendon reflexes absent (extensor plantar present), joint position and vibratory sense impaired, sometimes loss of pain and temperature, paralysis over course of 20 years. High incidence of diabetes and hypertrophic cardiomyopathy (dilated less common) and arrhythmias. 

===Friedreich's foot===
Seen in Friedreich's ataxia, pes cavus with hammer toe. 

===Friedreich's sign===
Exaggerated y descent in patients with increased venous pressure, associated with an S3; also associated with constrictive pericarditis. 

===Froin's syndrome===
Spinal block from tumor or inflammatory conditions, etc. causing increased protein in CSF, resulting in xanthochromia and increased coagulability in CSF. Described by Georges Froin, a French physician born 1874. 

===Froment's sign===
For diagnosis of ulnar nerve lesion; caused by flexor pollicus longus (median nerve) which comes into action when the patient attempts to grip a flat object between the thumb and the hand and causes flexion at the interphalangeal joint (rather than extension, as would be seen with normal use of the adductor pollicus). 

===Fuch's corneal dystrophy===
Most common indication for corneal transplantation, a progressive bilateral condition with corneal edema from dysfunction of the corneal endothelium. Occurs in 5% of people over age of 40. 

===Fukuyama congenital muscular dystrophy===
Congenital muscular dystrophy in combination with cortical dysgenesis (micropolygyria); autosomal recessive disorder, more common in Japan. Due to mutation in fukutin. 

==G==

===Gaisböck's syndrome===
Stress polycythemia, combination of modest elevation in hematocrit and normal red cell mass; unknown etiology, tends to be seen in middle-aged males, who smoke and are overweight and hypertensive. Described in 1905. 

===Galeazzi fracture===
Fracture of the radius at the junction of the middle and distal thirds accompanied by disruption of the distal radioulnar joint. 

===Galen, great vein of===
Great cerebral vein. 

===Gallavardin dissociation===
In aortic stenosis, high-velocity jet within the aortic root resulting in radiation of murmur upward to 2nd right intercostal space (in older patients, becomes harsh, noisy, and impure), whereas the murmur over apex is pure and often musical, mimicking mitral regurgitation. 

===Galloway-Mowat syndrome===
Autosomal recessive disorder characterized by early onset nephrotic syndrome, microcephaly, and hiatal hernia. 

===gamekeeper's thumb===
Injury to ulnar collateral ligament of the thumb. 

===Gandy-Gamna nodules===
In congestive splenomegaly, organization of focal hemorrhages giving rise to foci of fibrosis containing deposits of iron and calcium salts encrusted on connective tissue and elastic fibers. 

===Ganser syndrome===
A dissociative disorder characterized by giving nonsensical or approximate answers to questions; syndrome occurs most frequently in prisoners where it may represent an effort to obtain leniency. Described in 1898 by German psychiatrist Sigbert Ganser. 

===Garcin syndrome===
Extensive unilateral cranial palsies associated with malignancy in nasopharynx or skull base. 

===Gardner-Diamond syndrome===
Also known as psychogenic purpura; painful ecchymoses at site of trauma followed by progressive edema and erythema; associated with psychiatric disorders. Lesions have been likened to "religious stigmata." Initial mechanism felt to be autoerythrocyte sensitization with purpura following intradermal injection of patient's own RBC stroma. Initially described in 1955. 

===Gardner's syndrome===
Familial adenomatous polyposis with extraintestinal manifestations: 1. sebaceous cysts, 2. osteomas (particularly of the mandible, skull, and long bones), 3. desmoid tumors; mutation in adenomatous polyposis coli (APC) gene in 5q. Increasingly appreciated that FAP patients generally have extraintestinal manifestations. 

===Gardos channel===
Potassium-selective channel controlled by cytosolic calcium concentrations, one of two channels involved in red cell shrinkage playing a role in sickling; local tissue acidosis and deoxygenation-induced influx of calcium activate the Gardos channel resulting in shrinkage; clotrimazole potent blocker of this channel. 

===Garland's triad===
In sarcoidosis, triad of bilateral hilar lymphadenopathy, right paratracheal lymphadenopathy on chest radiograph. 

===Garré, sclerosing osteomyelitis of===
A chronic type of osteomyelitis where there is extensive new bone formation that obscures much of the underlying osseous structure; most commonly seen in the jaw in response to e.g. a dental infection. 

===gastrinoma triangle===
A triangle where more than 90% of extrapancreatic gastrinomas are located bordered by 1. 3rd portion of duodenum, 2. cystic duct, 3. pancreatic neck. 

===Gaucher's disease===
Most common lysosomal storage disease, autosomal recessive sphingolipidosis, from mutations in glucocerebrosidase gene on 1q21 (also known as acid beta-glucosidase). Enzyme cleaves glucose residue from ceramide. Type I, chronic non-neuropathic form, splenic and skeletal involvement; can be treated with infusions of macrophage-targeted human placental glucocerebrosidase, alglucerase (Ceredase), use described in 1991. Type II, acute infantile, most children die by age 2. Type III, chronic neuropathic form. 

===Gelineau's disease===
Narcolepsy. 

===Geraldi, fossa of===
Name of the fossa between the testicle and epididymis. 

===Gerbode defect===
Ventricular septal defect communicating directly between the left ventricle and right atrium. 

===Gerhardt's sign===
In aortic regurgitation, pulsation of the spleen in the presence of splenomegaly; see also Sailer's sign. 

===German measles===
Rubella. 

===Gerota's fascia===
Fascia surrounding the kidney. 

===Gerstmann syndrome===
Finger agnosia, agraphia, right-left disorientation, and dyscalculia. Associated with lesions in the dominant, parietal lobe. 

===Gerstmann-Straussler-Scheinker syndrome===
Slowly progressive cerebellar ataxia, beginning in 50-60s; due to mutation in prion gene. 

===Geschwind syndrome===
Personality syndrome in temporal lobe epilepsy characterized by viscosity, circumstantiality, hypergraphia (writing and drawing), and hyperreligiosity (Arch Gen Psychiatry 1975;32:1580). 

===Ghon lesion===
Primary area of tuberculosis infection. 

===Gianotti-Crosti syndrome===
Reactive exanthem, first described in association with hepatitis B infection (papular acrodermatitis of childhood, papular eruption on face and limbs); also associated with EBV, CMV infection. 

===Gibbs-Donnan effect===
Effect of charged particles on one side of a membrane on the distribution of other charged particles, when the former cannot diffuse through the membrane but the latter can. 

===Gilbert's syndrome===
With the exception of hemolytic anemias, most common cause of mild unconjugated hyperbilirubinemia from mild decrease in glucoronyltransferase activity, responds to phenobarbital, affects up to 7% of population. 

===Girdlestone procedure===
Femoral head ostectomy, resulting in fusion of hip in straight leg position. Used for treatment of septic hip arthritis and osteomyelitis, e.g. historically from tuberculosis. 

===Gitelman's syndrome===
Variant of Bartter's syndrome where patients have hypomagnesemia and hypocalciuria due to mutations in thiazide-sensitive sodium-chloride transporter. 

===Glanzmann's thrombasthenia===
Inherited disorder of platelet function where Gp IIb/IIIa receptor for fibrinogen missing. 

===Glasgow coma scale===
Scale for assessing state of consciousness, initially described for head trauma; three components, best eye response, best verbal response, best motor response. Scale ranges from 3 (deep coma or death) to 15 (fully awake). Scale published in 1974 by Graham Teasdale and Bryan J. Jennett at University of Glasgow. 

===Glauber's salt===
Sodium sulfate, laxative. 

===Gleason score===
Prostate cancers stratified into 5 grades on basis of glandular patterns and degree of differentiation; grade 1 most differentiated and grade 5 no glandular differentiation; primary score and secondary score (for second most common histology) added together for score; therefore most differentiated tumor score of 2. 

===Gleich syndrome===
Episodic angioedema with eosinophilia characterized by recurrent episodes of angioedema, urticaria, pruritus, fever, weight gain, elevated IgM, leukocytosis, and marked eosinophilia; blood eosinophilia parallels disease activity (N Engl J Med 1984;310:1621); no end-organ involvement or cardiac damage unlike other eosinophilc syndromes. 

===Glenn shunt===
For treatment of hypoplastic left heart syndrome. Unidirectional: SVC to right pulmonary artery anastomosis with ligation of the proximal RPA and cardiac end of the SVC. Bidirectional: SVC to right pulmonary artery anastomosis with flow to both the RPA and LPA. 

===Glisson's capsule===
Liver capsule. 

===Goetz sign===
In patent ductus arteriosus, jet of unopacified blood from aorta into opacified blood of pulmonary artery. 

===Goldblatt kidney===
Atrophic kidney from vasoconstriction of renal artery; results in hypertension. 

===Goldenhar syndrome===
Hemifacial microsomia or oculoauriculovertebral dysplasia, characterized by unilateral deformity of the external ear and small ipsilateral half of the face with epibulbar lipodermoid and vertebral abnormalities; autosomal dominant. 

===Goldie-Coldman hypothesis===
Malignant cells likely to acquire spontaneous resistance to cytotoxic drugs as they progressively grow and divide, even without any exposure to those drugs. 

===Golgi apparatus===
Membranous cell structure that processes proteins synthesized in the endoplasmic reticulum. 

===Goltz syndrome===
Focal dermal hypoplasia, X-linked dominant disease characterized by patchy dermal hypoplasia, herniation of fat into the dermis, dystrophic nails, sparse, brittle hair; due to mutation in PORCN, which affect regulation of Wnt signaling. 

===Gonda's maneuver===
Extensor plantar response by flicking the little toe suggesting upper motor neuron defect. 

===Goodell's sign===
Softening of cervix associated with pregnancy that occurs at around 8th week. 

===Goodpasture's syndrome===
Glomerulonephritis characterized by linear deposits of antibody along the glomerular basement membrane, antibodies interact with alveolar wall, leading to pulmonary hemorrhage and pulmonary fibrosis. Goodpasture antigen resides in the noncollagenous portion of the alpha3 chain of collagen type IV; high prevalence of DRW15/DQW6, also see iron-deficiency anemia. 

===Good's syndrome===
Immunodeficiency, hypogammaglobulinemia associated with thymoma (mainly thymoma of spindle cell type); associated with recurrent pulmonary infections; described by Good in 1954. 

===Goodsall's rule===
Anal fistulae course in a straight path anteriorly and take a curved path posteriorly. 

===Gordon's maneuver===
Extensor plantar response by squeezing the calf muscle suggesting upper motor neuron defect. 

===Gordon's syndrome===
Type 2 pseudohypoaldosteronism associated with volume expansion, hypertension, and otherwise normal renal function; felt be to be due to enhanced distal chloride reabsorption. 

===Gorham-Stout disease===
Non-malignant osteolysis from intraosseous proliferation of vascular tissue; also known as vanishing or disappearing bone disease; IL-6 v. PDGF signaling felt to have pathogenic role. 

===Gorlin-Goltz syndrome===
Focal dermal hypoplasia characterized by widespread lesions of dermal hypoplasia with herniation of adipose tissue, streaks of pigmentary disturbance following lines of Blaschko, and severe absence deformities of bone, mental retardation, defects of optic nerve. 

===Gorlin's syndrome===
Increased incidence of basal cell carcinoma, medulloblastoma, and rhabdomyosarcoma; attributed to heterozygous mutation in Patched, a negatively acting component of the Hedgehog receptor. 

===Gottron's papules===
In dermatomyositis, scaling erythematous eruption or dark red patches over the knuckles, elbows, knees; may mimic psoriasis. 

===Gower's maneuver===
In Duchenne's muscular dystrophy, patient using hands to help himself get up. 

===Graafian follicle===
Small fluid-filled sac in ovary containing maturing egg; described by Regnier de Graaf (1641-1673), Dutch physician. 

===Gradenigo's syndrome===
Thrombosis of inferior petrosal sinus producing ipsilateral facial pain, lateral rectus muscle weakness. 

===Grafenberg spot===
Erogenous area in anterior vaginal wall. 

===Graham patch===
Piece of omentum used for repairing perforations. 

===Graham Steell murmur===
Early diastolic murmur of pulmonic regurgitation secondary to pulmonary hypertension, best heard in left 2nd interspace, may be indistinguishable from murmur of aortic regurgitation; occurs in 12% of patients with tricuspid regurgitation; described by Graham Steell. 

===Graham-Little syndrome===
End-stage lichen planus of the scalp resulting in scarring alopecia of the scalp. 

===Graves's disease===
Hyperthyroidism with diffuse goiter, ophthalmopathy, dermopathy from thyroid-stimulating immunoglobulin. 

===Grawitz tumor===
Renal cell carcinoma. 

===Gregg effect===
Augmentation of left ventricular systolic performance with increase in coronary flow and perfusion pressure. 

===Greig cephalopolydactyly syndrome===
Rare autosomal dominant developmental disorder characterized by craniofacial abnormalities and post-axial and pre-axial polydactyly as well as syndactyly of hands and feet from mutation in GLI3. See also Pallister-Hall syndrome. 

===Grey Turner's sign===
Blue-black discoloration around the flanks, e.g. in acute hemorrhagic pancreatitis (1-2%) and other causes of retroperitoneal hemorrhage. Named after English surgeon George Grey Turner. See also Cullen's sign. 

===Griffith's point===
Watershed area in splenic flexure; see also Sudeck's point. 

===Griffith's sign===
In thyrotoxicosis, lag of the lower lids during elevation of the globes. 

===Griscelli syndrome===
Primary immunodeficiency syndrome associated with partial "albinism"; presents similarly to Chédiak-Higashi syndrome but without the giant intracytoplasmic inclusions. From defect in exocytosis of cytolytic granules; due to mutation in RAB27A, a member of the RabGTPase family or mutation in myosin-Va. 

===Grover's disease===
Transient acantholytic dermatosis; most common in males over 40, sudden onset of pruritus across trunk, neck, and proximal limbs; a polymorphic, pruritic, papulovesicular dermatosis characterized histologically by acantholysis. 

===Guam disease===
Guam amyotrophic lateral sclerosis-parkinsonism-dementia linked to a plant excitant neurotoxin found in cycad plant eaten by Chamorro people, toxin believed to be excitotoxin beta-N-methylamino-L-alanine, a low-potency convulsant (Science 1987;237:517-22). 

===Guillain-Barré syndrome===
Acute idiopathic polyneuropathy that may follow minor infective illnesses, inoculations, or surgical procedures (suggested association with C. jejuni) resulting in immunologically-mediated demyelination and progressive weakness. 

===Gull's disease===
Myxedema. 

===Gunn's sign===
Tapering of veins on either side of AV crossing in hypertensive retinopathy (grade 3); see also Salus's sign and Bonnet's sign. 

===Gunther's disease===
Autosomal recessive congenital erythropoietic porphyria from decreased URO synthase activity, hemolytic anemia, cutaneous lesions characterized by mutilating photodermatitis. 

===Guthrie test===
For diagnosis of phenylketonuria, a bacterial assay for presence of high levels of phenylalanine in patient's serum; high phenylalanine allows for growth of bacteria in the presence of an inhibitor. Developed by Guthrie in 1962. 

===Guyon's tunnel===
Ulnar tunnel. 

==H==
===Haab's striae===
Lines in Desçemet's membrane; associated with congenital glaucoma. 

===Haff disease===
Unexplained rhabdomyolysis in people who have eaten fish in the 24 hours before onset of symptoms; first described in the summer and fall of 1924 when physicians near the Haff shores along the Baltic coast recognized an outbreak; attributed to an unidentified toxin. 

===Hageman factor===
Factor XII, named after patient John Hageman. Interestingly, patient died of a pulmonary embolism after traumatic left hip fracture. Deficiency not associated with bleeding, but may increase risk of thrombosis. 

===Hailey-Hailey disease===
Familial benign pemphigus; described by Hailey brothers in 1939. From mutation in calcium pump, ATP2C1. 

===Hajdu-Cheney syndrome===
Extremely rare syndrome with excessive bone resorption, leading to osteoporosis; affects the outermost bones of the fingers and toes. 

===Hakim-Adams syndrome===
Normal pressure hydrocephalus. 

===Haldane effect===
Deoxygenated hemoglobin having a greater affinity for CO2 than oxygenated hemoglobin. 

===Hallermann-Streiff syndrome===
Autosomal recessive syndrome with bird-like facies with hypoplastic mandible and beaked nose, proportionate dwarfism, hypotrichosis, microphthalmia, and congenital cataract. 

===Hallervorden-Spatz disease===
Autosomal recessive juvenile-onset generalized neuroaxonal dystrophy characterized by progressive movement alterations such as dystonia, tardive dyskinesia, rigidity, choreoathetosis, pyramidal signs, mental retardation, and iron accumulation in the brain; associated with mutation in pantothenate kinase 2. Hallervorden, Nazi pathologist involved in Aktion T-4 adult euthanasia program. 

===Hamburger shift===
In red blood cells, the conversion of carbon dioxide ultimately to bicarbonate, which diffuses out in exchange for chloride ions diffusing in. 

===Hamman-Rich syndrome===
Acute interstitial pneumonia, a rare fulminant form of lung injury that presents acutely (days to weeks from onset of symptoms). Most commonly occurs in previously healthy individuals, characterized by a temporally uniform lesion which reflects an episode of acute lung injury at a single point in time (different from usual interstitial pneumonia where lesions are different age); path shows diffuse alveolar damage (a nonspecific reaction pattern). 

===Hamman's sign===
Mediastinal crunch or precordial crackles synchronous with the heart beat, not with respiration. Best heard in the left lateral position. Associated with mediastinal emphysema (pseudomediastinum), seen with Boerhaave's syndrome. 

===Hampton's hump===
In pulmonary embolism or infarction, a wedge-shaped infiltrate that abuts the pleura; often associated with a small pleura effusion that is usually exudative and may be hemorrhagic; not specific. 

===Hampton's line===
Radiolucent collar of granulation tissue across the base of a gastric ulcer. 

===Ham's test===
For diagnosing paroxysmal nocturnal hemoglobinuria, increased sensitivity of PNH-affected RBCs to lysis by complement; introduced in late 1930s. 

===Hand-Schüller-Christian triad===
In multifocal Langerhans' cell histiocytosis, triad of calvarial bone defects, diabetes insipidus, and exophthalmos. 

===hangman's fracture===
Fracture of pars interarticularis of C2 vertebra, often from hyperextension injury. 

===Hannington-Kiff sign===
Ipsilateral loss of the adductor reflex with preservation of patellar reflex in strangulated obturator hernia. 

===Hansel's stain===
Special stain used to detect eosinophiluria in the urine sediment. 

===Hansen's disease===
Leprosy. 

===Hardy-Weinberg equilibrium===
p^2 + 2pq + q^2 for describing the frequency of these genotypes; sexual reproduction doesn't cause a constant reduction in genetic variation in each generation but remains constant. 

===harlequin syndrome===
Localized autonomic syndrome of heat or exercised-induced flushing and sweating limited to one side of the face with impairment of sweating and flushing on the contralateral side; possible link with Holmes-Adie syndrome. 

===Harrison's groove===
Site at lower margin of thorax where diaphragm attaches to the ribs. Groove more prominent in rickets due to lack of calcium necessary to harden site of attachment. 

===Hartmann's procedure===
Proximal colostomy followed by stapled-off colon or rectum that is left in the peritoneal cavity. 

===Hartnup disease===
An autosomal recessive disorder in which there is a reduction of small-intestinal and renal transport of certain neutral amino acids, including (Trp, a precursor of niacin), causing elevated amino acid excretion in urine and feces; characterized by failure to thrive, photosensitivity, ataxia; from mutation in SLC6A19. 

===Hashimoto-Pritzker disease===
Pure cutaneous form of Langerhans cell histiocytosis. 

===Hashimoto's encephalopathy===
Neurologic complication of Hashimoto's thyroiditis, mainly in people euthyroid, associated with a vasculitic condition with stroke-like episodes and cognitive impairment and diffuse progressive picture with dementia, seizures, movement disorders, psychosis, and sometimes delirium. 

===Hashimoto's thyroiditis===
Goitrous chronic autoimmune thyroiditis; in areas with sufficient iodine, elevated TSH is often viewed as evidence of chronic autoimmune thyroiditis as well as antithyroid antibodies; antithyroglobulin antibodies in 60% of patients and antithyroid microsomal antibodies in 95%. Described in 1920. 

===Hassall's corpuscles===
Spherical or ovoid bodies found in the medulla of the thymus, composed of concentric arrays of epithelial cells around central area of degenerated cells. Numbers increase until puberty, then decreases. 

===Hatchcock's sign===
Upward pressure applied to the angle of the mandible (ramus) produces tenderness with mumps but no tenderness with adenitis. 

===Haw River syndrome===
Variant of dentalorubral-pallidoluysian atrophy (DRPLA) (ataxia and rigidity accompanied by choreoathetosis, myoclonic epilepsy, and dementia) but without the myoclonic epilepsy; described in ancestors born in Haw River, North Carolina; caused by same expanded CTG-B37 repeat as in DRPLA. 

===Hawkin's sign===
In shoulder impingement, with the arm in a throwing position and flexed forward about 30 degress, forcibly internally rotate the humerus; pain suggests impingement of the supraspinatus tendon against the coracoacromial ligament. 

===Hawthorne effect===
The effect (usually positive or beneficial) of being under study upon the persons being studied; their knowledge of the study often influences behavior. Named after city in Illinois; site of a Western Electric plant. 

===Heberden's nodes===
Characteristic in women, but not in men, represent prominent osteophytes at the distal interphalangeal joints in osteoarthritis (enlargements of tubercles at the articular extremities of the distal phalanges). 

===Hecht-Beals syndrome===
Trismus-pseudocamptodactyly syndrome, inability to open mouth fully and problems with wrist dorsiflexion, producing involuntary flexion contracture of distal and proximal interphalangeal joints. Associated with mutation in MYH8. 

===Heck's disease===
Oral focal epithelial hyperplasia associated with HPV 13, 32 infection. 

===Heerfordt-Waldenström syndrome===
Sarcoidosis associated with fever, parotid enlargement, anterior uveitis, and facial nerve palsy. 

===Hegar's sign===
Softening of the uterus at the junction between the cervix and the fundus during the first trimester of pregnancy. 

===Heimlich maneuver===
Abdominal thrust maneuver for clearing airway (blocked by foreign object, e.g. food) described in 1974 by Henry Heimlich . 

===Heineke-Mikulicz pyloroplasty===
Longitudinal incision through all layers of the pylorus, sewed closed in a transverse direction to make the pylorus nonfunctional (used after truncal vagotomy). 

===Heiner syndrome===
Cow milk allergy associated with pulmonary infiltrates, pulmonary hemosiderosis, anemia, recurrent pneumonia and failure to thrive. 

===Heinz bodies===
Seen in unstable hemoglobin and oxidant stress; precipitates of denatured hemoglobin on red blood cells; only visible when blood is supravital stained (crystal violet); not seen on routine blood smears. 

===Heister, spiral valves of===
Found in the neck of the gallbladder, where tiny folds of mucosal epithelium coalesce to form these valves, may assist in retaining bile between meals. 

===HELLP syndrome===
Hemolysis, elevated liver function tests, and low platelets; microangiopathic process seen in third trimester of pregnancy; seen in 20% of preeclampsia. 

===hemoglobin Bart's===
Four gamma globin chains, seen in hydrops fetalis (alpha thalassemia), very high oxygen affinity. 

===hemoglobin Constant Spring===
Particularly common structural variant with alpha thalassemia in Asia, contains mutation which abolishes normal translation termination codon, so extra 31 residues read until another in-frame termination codon comes up. 

===hemoglobin Gower===
Embryonic, primitive hemoglobin. Gower 1, zeta2 episilon2; Gower 2, alpha2 epsilon2. 

===hemoglobin Lepore===
No beta chain; delta chain by delta-beta hybrid. 

===hemoglobin Portland===
Zeta2gamma2, primitive embryonic hemoglobin, can be seen more prominently in e.g. hemoglobin Bart hydrops fetalis. 

===HEMPAS===
Hereditary Erythrocyte Multinuclearity and Positive Acidified Serum test, also known as congenital dyserythropoietic anemia type II. A congenital anemia characterized by multinucleated red cell precursors and hemolysis of red blood cells of the patient with autologous serum during Ham's test. 

===Henle, loop of===
Section of nephron between proximal and distal tubule located in the medulla and involved in reabsorbing 25-35% of filtered NaCl and reaborbing NaCl in excess of water. 

===Henle's layer===
The outer layer of cells of the inner root sheath of a hair follicle, lying between the outer root sheath and Huxley's layer. 

===Henoch-Schönlein purpura===
Systemic vasculitis with deposition of immune complexes containing IgA in skin and kidney, occurring mainly in in young children. Characterized by purpuric rash, colicky abdominal pain (presumably due to focal hemorrhages into the GI tract), polyarthralgia, and acute glomerulonephritis. May occur following infection with group A streptococci, viral infections; majority of cases, unknown cause. 

===Hering, canals of===
At the fringes of the portal tract, from the joining of bile canaliculi. 

===Hering-Breuer reflex===
Reflex mediated by stretch receptor in smooth muscle of airways responsible for apnea, i.e. decreased breathing frequency, as a result of lung inflation. 

===Hering's nerve===
Carotid sinus nerve, CN IX, carries information to the vasomotor center in the brainstem. 

===Herlitz syndrome===
Epidermolysis bullosa lethalis; mutation that prevents the folding of laminin 5. Described by Gillis Herlitz, Swedish pediatrician, born 1902. 

===Hermansky-Pudlak syndrome===
Autosomal recessive syndrome from defect in AP-3 adaptor complex beta3A subunit or HPS1; characterized by idiopathic pulmonary fibrosis, oculocutaneous albinism, a platelet storage pool deficiency, and ceroid lipofuscinosis from defects of multiple cytoplasmic organelles: melanosomes, platelet dense granules and lysosomes. 

===Herring bodies===
Neurosecretory granules consisting of either vasopressin or oxytocin in neurohypophysis. 

===Hers disease===
Type VI glycogen storage disease, deficiency in liver phosphorylase; presents as hepatomegaly and growth retardation; hypoglycemic, hyperlipidemia, and hyperketosis usually mild if present; hepatomegaly and growth retardation improve with age and usually disppear at puberty. 

===Heschl's gyrus===
Primary auditory cerebral cortex, transverse temporal gyrus. 

===Hess test===
See Rumpel-Leede sign; a test for capillary fragility by applying pressure with blood pressure cuff and counting petechiae; noticed phenomenon while treating children with scurvy. 

===Hesselbach's triangle===
Where direct inguinal hernias occur, bound by the inguinal ligament, inferior epigastric artery, and rectus abdominus muscle. 

===Heyde's syndrome===
Association between bleeding from gastrointestinal angiodysplasia and severe aortic stenosis which may resolve with aortic valve replacement. May also be explained by acquired type IIA von Willebrand's disease. First described by Heyde in N Engl J Med 1958;259:196. 

===Hibernian fever, familial===
TNF Receptor-1 Associated Periodic Syndrome (TRAPS), autosomal dominant. From mutation in TNFR1. Characterized by recurrent fevers, myalgias, conjunctivitis, periorbital edema, abdominal pain, arthritis, rash (single or multiple erythematous patches that spread distally down an extremity). 

===Hickam's dictum===
A "patient can have as many diseases as they damn well please", attributed to John Hickam, a faculty member at Duke University in the 1950's, and was later chairman of medicine at Indiana University; see also Occam's razor. 

===Hickey-Hare test===
In evaluating hypernatremia, 5% NaCl infused at a rate of 0.05 mL/kg/min followed by measurements of urine volume and urine osmolality. 

===Hill's sign===
In aortic regurgitation, refers to popliteal cuff systolic pressure exceeding brachial cuff pressure by more than 60 mm Hg. 

===Hill-Sachs lesion===
Posterolateral humeral head indentation fracture from anterior shoulder dislocation; from humeral head impinging against glenoid of shoulder joint. 

===Hinton test===
Test for diagnosing syphilis using a precipitin of glycerol, cholesterol, and beef heart extract; developed in 1927. 

===Hippocratic fingers===
Clubbing. 

===Hippocratica, facies===
The mask of death following peritonitis, i.e. as a result of vomiting and hypotension, anxious face with hollow cheeks and dim eyes. 

===Hirano bodies===
In Alzheimer's disease, intracytoplasmic proximal dendritic eosinophilic inclusions consisting of actin. 

===Hirata disease===
Insulin autoimmune syndrome with hypoglycemia associated with insulin autoantibodies. Third leading cause of spontaneous hypoglycemia in Japan; rare in Western countries. 

===Hirschberg test===
Corneal light reflex test. 

===Hirschsprung's disease===
Congenital aganglionic megacolon; colonic dilatation proximal to an aganglionic, contracted distal colon and rectum; caused by gestational failure of neural crest cells to migrate to distal colon. Autosomal dominant form associated with mutations of the RET gene, autosomal recessive form associated with mutations of the endothelin-B-receptor gene. 

===Hitzig zones===
In tabes dorsalis from syphilis, regions of reduced sensation found in central face, nipples, ulnar forearms, and peroneal legs, leading to painless ulcers and joint damage. 

===Hodgkin's disease===
Lymphoma characterized by arising in a single node or chain of nodes, spreading in anatomically contiguous nodes. Reed-Sternberg cells are one hallmark. 

===Hoesch test===
Diagnostic test for urinary porphobilinogen for porphyria; see also Watson-Schwartz reaction. 

===Hoffmann's sign===
Involuntary flexion of the digits when tapping or striking over the palmar digital aspects of the 2nd, 3rd, and 4th digits in upper motor neuron defect. 

===Hoffman's syndrome===
In hypothyroidism, diffuse muscle hypertrophy, accompanied by stiffness, weakness, painful muscle cramps, associated with elevated muscle enzymes. 

===Hoigne reaction===
Pseudoanaphylactic reaction, complication associated with intramuscular procaine penicillin, occurs in 1/1000 patients; characterized by tachycardia, elevated blood pressure, fear of imminent death, violent combativeness, unusual taste sensation, auditory or visual disturbances; rarely lasts longer than 30 min. Felt to be due to inadvertent intracapillary infusion of the procaine component resulting in microembolization. 

===Hollenhorst plaques===
Cholesterol emboli visible as small bright flecks lodged in arterial bifurcations in retina. 

===Holmes tremor===
Symptomatic tremor caused by lesions in the brainstem, cerebellum, or thalamus; postural and/or action in nature and worsen during movement and markedly increase during goal-directed movements; affect predominantly proximal limbs, low frequency;. Also known as rubral or midbrain tremor. 

===Holmes-Adie syndrome===
Most frequently occurs in young women, large, often irregular pupils, unilateral at onset as well as segmental palsy and segmental spontaneous movement of the iris, delayed constriction in response to near vision, delayed redilation after near vision, impaired accommodation, absent light reflex, and absent deep tendon reflexes. May be caused by degeneration of ciliary ganglion from viral or bacterial infection, followed by aberrant reinnervation of the pupilloconstrictor muscles. 

===Holmes's heart===
Single ventricle with normally-related great arteries. 

===Holter monitor===
Continuous ambulatory EKG monitoring; first described by Montana physician Normal Holter in 1949 (Science 1961;134:1214-1220). 

===Holt-Oram syndrome===
Autosomal dominant syndrome, dysplasia of the upper limbs and atrial septal defect, reduction anomalies of the upper limbs, heart-hand syndrome from mutation in TBX5. 

===Homans's sign===
In deep venous thrombosis, pain and tenderness on compression of the calf muscles (by either squeezing the calf muscles or forced dorsiflexion of the foot). 

===Homer-Wright pseudorosettes===
In neuroblastoma, tumor cells arranged about a central space filled with fibrillar extensions of the cells. 

===honeymooner's palsy===
Radial nerve palsy from compression of nerve between middle third of the humerus between the brachoradialis and forearm extensor muscles. 

===Hoover's sign===
A modification in the movement of the costal margins during respiration, caused by a flattening of the diaphragm; suggestive of empyema or other intrathoracic condition causing a change in the contour of the diaphragm. 

===Hoover's sign===
In hysterical, non-organic weakness, patient does not push down into your hand with contralateral extremity when you ask patient to lift weak extremity. 

===Hopkins syndrome===
Poliomyelitis-like illness associated with acute asthma in childhood. 

===Horner's syndrome===
Enophthalmos, ptosis, miosis, and anhidrosis, unilateral from lesion affecting sympathetic innervation of eye. If present since infancy, the ipsilateral iris is lighter and blue (heterochromia iridis); topical 4% cocaine will dilate normal pupil but not a desympathectomized pupil. Associated with Pancoast tumor, due to involvement of paravertebral sympathetic chain and the inferior cervical ganglion. 

===Horton's cephalalgia===
Cluster headache; also known as histaminic cephalalgia. 

===Horton's disease===
Temporal arteritis. 

===Hounsfield unit===
Scale named after inventor of computed tomography and Nobel prize winner, Sir Godfrey N. Hounsfield (1919-2004), water 0 H, -1024 H for air to 3000-4000 H for bone, relative scale. 

===Houston, valve of===
Rectal valves: superior, middle, and inferior. 

===Howell-Evans syndrome===
Inherited tylosis (keratoderma of palms and soles), strongly associated with esophageal squamous cell carcinoma. 

===Howell-Jolly body===
In asplenia or malfunctional spleen, nuclear remnants on red blood cells as small, round, darkly-stained nuclear fragments; no special stains necessary; larger than Pappenheimer bodies. 

===Howship-Romberg sign===
Pain along the inner aspect of the thigh; seen with an obturator hernia due to nerve compression. 

===Howship's lacunae===
Resorption pits on bone formed by osteoclasts. 

===Hughes syndrome===
Antiphospholipid antibody syndrome; described in 1983 by Graham Hughes (Clin Exp Dermatol 1984;9:535). 

===Hughes-Stovin syndrome===
Multiple pulmonary artery aneurysms with peripheral venous thrombosis. 

===Humphrey's ligament===
Anterior meniscofemoral ligament. 

===Hunner's ulcer===
In 10% of interstitial cystitis, lesions that involve all layers of the bladder wall and appear as brownish-red patches on the bladder mucosa. 

===Hunter's ligament===
Round ligament of uterus. 

===Hunter's syndrome===
Mucopolysaccharidosis (II), iduronate sulfatase deficiency, X-linked, affecting degradation of dermatan sulfate and heparan sulfate, resulting in physical deformity and mental retardation, no corneal clouding. 

===Huntington's disease===
Autosomal dominant neurodegenerative disease from expanded CAG trinucleotide repeat 4p16.3 associated with chorea initially as restlessness, psychiatric symptoms, and dementia; Westphal variant, atypical variant where there is progressive rigidity and akinesia with little or no chorea. 

===Hurler's syndrome===
Autosomal recessive mucopolysaccharidosis type I caused by deficiency of alpha-L-iduronidase, with consequent accumulations of the mucopolysaccharides heparan sulfate and dermatan sulfate in the heart, brain, liver, and other organs; progressive deterioration, hepatosplenomegaly, dwarfism, gargoyle-like facies, stubby fingers, corneal clouding, progressive mental retardation, and death by age 10. 

===Hurler-Scheie syndrome===
Mucopolysaccharidosis I caused by deficiency of alpha-L-iduronidase (severe form is Hurler's syndrome), have same problems as Hurler's syndrome but progression is lower, mild or no mental retardation, and death in teens or 20s. 

===Hurst's disease===
Acute hemorrhagic leukoencephalitis, a fulminant form of acute disseminated encephalomyelitis. 

===Hürthle cells===
In Hashimoto's thyroiditis, deeply stained colloid or clusters of cells having an abundant, brightly eosinophilic granular cytoplasm, thought to represent a degenerated state of the follicular epithelium. 

===Hutchinson freckle===
Lentigo maligna, a nonfamilial precursor to lentigo maligna melanoma. 

===Hutchinson pupil===
Dilated and unreactive pupil on side of intracranial lesion, from compression of ipsilateral oculomotor nerve; also seen in uncal herniation. Named after Sir Jonathan Hutchinson (1828-1913). 

===Hutchinson-Gilford syndrome===
Also known as progeria, a condition where there is normal development in the first year followed by gross retardation of growth, with a senile appearance characterized by dry wrinkled skin, total alopecia, and bird-like facies; genetics unclear. 

===Hutchinson's sign===
In herpes zoster ophthalmicus, vesicular rash at nasal tip indicating involvement of the external nasal branch of CN V; associated with increased incidence of ocular involvement. 

===Hutchinson's sign===
Pigment in the paronychial area suggesting melanoma. 

===Hutchinson's teeth===
A sign of congenital syphilis, teeth that are smaller and more widely spaced than normal; notched biting surfaces. 

===Hutchinson's triad===
Congenital syphilis manifesting late at around 2 years old with triad of interstitial keratitis, notched incisors, and eighth nerve deafness. 

===Huxley's layer===
A layer of the inner root sheath of a hair follicle, lying between Henle's layer and the inner sheath cuticle. 

==I==
===I-cell disease===
Lysosomal storage disorder, from deficiency of ability to phosphorylate mannose, causing an incorrect targeting of potential lysosomal enzymes to extracellular sites instead of lysosomes, characterized by skeletal abnormalities, restricted joint movement, coarse facial features, severe pscyhomotor impairment, death by 8 y.o. 

===Imerslund-Grasbeck syndrome===
Juvenile megaloblastic anemia, an autosomal recessive condition involving mutation in cubulin, receptor that binds IF-B12 complex; also associated with proteinuria. 

===Irish's node===
Left axillary adenopathy associated with metastatic disease, e.g. gastric cancer. 

===Isaacs's syndrome===
Neuromyotonia; continuous muscle stiffness, rippling muscle movements (myokymia), delayed relaxation following muscle contraction believed to be due to autoantibodies to presynaptic potassium channels. 

===Ishihara plates===
Pseudoisochromatic plates (plates with color dots for numbers) for testing color vision. Described by Shinobu Ishihara, Japanese ophthalmologist (1879-1963). 

===Ishikawa's sign===
In cystic adventitial disease of the popliteal artery, disappearance of foot pulses on knee flexion or after exercise in patients. 

===itai-itai disease===
Bone disease from cadmium toxicity, characterized by multiple fractures, mixed pattern of osteoporosis and osteomalacia, and renal damage. Means "ouch-ouch" in Japanese, cadmium toxicity noted in exposed individuals living in Jinzu river basin in Japan who used river water contaminated with cadmium for irrigating rice fields. 

===Ito cells===
Vitamin A fat-storage cells, of mesenchymal origin found in the space of Disse; during development of cirrhosis, they become activated, transform into fibroblast-like cells. 

===Ivor Lewis procedure===
Esophagectomy through right thoracotomy and intrathoracic esophagogastric anastomosis; described in 1946 by Ivor Lewis. 

==J==
===Jaccoud's arthritis===
In systemic lupus erythematosus (SLE), ulnar deviation of the fingers, swan neck deformities, and subluxations, initially reversible since not joint problem per se but can become fixed over time. 

===jacksonian march===
In simple partial seizures, clonic movements of a single muscle group spreading to involve contiguous regions of the motor cortex. 

===Jackson-Weiss syndrome===
Craniosynostoses as well as limb defects, broad great toes. Due to mutations in FGFR2. 

===Jacobsen syndrome===
Congenital condition from deletion in 11q (especially FLI1 gene), characterized by learning disabilities, heart defects, and thrombocytopenia; see also Paris-Trousseau syndrome. 

===Jacquemier's sign===
Early sign of pregnancy characterized by purplish coloration of vagina. 

===Jadassohn, nevus sebaceus of===
Circumscribed hamartoma involving skin with a preponderance of sebaceous glands. Usually seen at birth or in early childhood. Described by Jadassohn in 1895. 

===Jamaican vomiting sickness===
Poisoning from hypoglycin A in unripe ackee fruit. Hypoglycin A is potent hypoglycemic agent that decreases rate of fatty-acid beta oxidation probably by inhibition of acyl dehydrogenase flavin-dependent oxidation. Causes liver damage indistinguishable from Reye's syndrome. 

===James fibers===
Tracts of atrial tissue running from the atria and inserting into the low AV node; functional significance not well established, controversial if associated with abnormal AV conduction. 

===Janeway lesions===
In infective endocarditis, nonpainful, small, erythematous or hemorrhagic macules or nodules of palms or soles. More common in acute bacterial endocarditis, but may occur in subacute bacterial endocarditis. 

===Jansen metaphyseal chondrodysplasia===
An autosomal dominant form of dwarfism resulting from an activating mutation in the parathyroid hormone receptor, premature ossification from acceleration of the transition from proliferative to hypertrophic chondrocytes. 

===Jansky-Bielschowsky disease===
Late infantile neuronal ceroid lipofuscinosis, CLN2 disorder generally characterized by visual loss, epilepsy, and psychomotor deterioration. Due to mutation in TPP1 gene. 

===Jarisch-Herxheimer reaction===
Sudden fevers, rigors, and persistent hypotension following antimicrobial treatment of louse-borne relapsing fever (spirochete Borrelia recurrentis infection) or syphilis; treatment with anti-TNF-alpha Fab before penicillin suppresses this reaction (NEJM 335:311). 

===Jatene's arterial switch===
For treating transposition of great vessels, pulmonary artery and aorta are transected above valves and switched, and coronary arteries are moved from old aortic root to new aorta (former pulmonary root). 

===Jefferson fracture===
Fracture of C1 at more than one site; rarely associated with neurological deficits because of size of spinal canal at this level. 

===Jendrassik maneuver===
For increasing sensitivity of deep tendon reflexes, have patient clasp hands together or grab wrists tightly while checking reflexes. Described by Hungarian physician Erno Jendrassik (1858-1921). 

===Jerusalem syndrome===
Psychosis affecting visitors to Jerusalem whereby afflicted develop psychotic religious delusions; affects a handful of visitors each year. 

===Jervell-Lange-Nielsen syndrome===
Long QT syndrome with congenital deafness, autosomal recessive. 

===Job's syndrome===
Hyperimmunoglobulin E syndrome. Immune deficiency where neutrophils fail to respond to chemotactic stimuli, associated with high levels of IgE; patients susceptible to cold staphylococcal abscesses. Associated with mutation in STAT3 in autosomal dominant version. 

===Jod-Basedow phenomenon===
Thyroid hyperfunction induced by excess iodine ingestion in patients with various thyroid disorders; "jod" is German for iodine; K. A. Von Basedow. 

===Joffroy sign===
In thyrotoxicosis, absence of forehead wrinkling with upward gaze and head tilted down, in setting of exophthalmos. Also, disorder of the arithmetic faculty in the early stages of organic brain disease. 

===Johanson-Blizzard syndrome===
Syndrome of nasal alar hypoplasia, hypothyroidism, pancreatic achylia, and congenital deafness; due to defect in UBR1 gene. 

===John Thomas sign===
Positive sign when penis inclined to side of the disorder radiographically (e.g., fractured hip); 70% sens 67% specific for John Thomas sign in hip fracture, Med J. Aust. 1998;169:670. Also known as Throckmorton sign. 

===Johnson-McMillin syndrome===
Autosomal dominant neuroectodermal syndrome characterized by anosmia, hypogonadotropic hypogonadism associated with conductive deafness, alopecia, congenital heart defects. 

===Jolly test===
In myasthenia gravis, a sequence of repetitive nerve stimulation (RNS) studies specifically designed to look for neuromuscular junction disease. A positive test is a &gt;10% decremental response with 3 Hz repetitive stimulation, 50-80% sensitive. After Friedrich Jolly, German neurologist, 1844-1904. 

===Jones criteria===
For diagnosing rheumatic fever, major criteria: carditis, polyarthritis, chorea, erythema marginatum, and subcutaneous nodules. minor criteria: arthralgia, fever, elevated ESR, CRP, prolonged PR. In setting of antecedent group A streptococcal infection, two major or one major and 2 minor suggests RF. Throat cultures negative by the time rheumatic fever appears. Described by Jones in 1944. 

===Jones's fracture===
Fracture at the base of the fifth metatarsal diaphysis. 

===Joubert syndrome===
Autosomal recessive disorder consisting of cerebellar hypoplasia, hypotonia, developmental delay, abnormal respiratory patterns, and abnormal eye movements. On brain imaging, see "molar tooth" sign. 

===Jumping Frenchmen of Maine syndrome===
Unusually extreme startle reaction that occurs in selected populations with reactions including echolalia, echopraxia; first described in French Canadian lumberjacks in the Moosehead Lake Region of Maine in the late 19th century; also described as latah in Malaysia. 

==K==
===kabuki syndrome===
Congenital mental retardation syndrome; postnatal dwarfism, a peculiar facies with long palpebral fissures, eversion of lateral third of the lower eyelids (reminiscent of the make-up of actors of Kabuki, a Japanese theatrical form), a broad and depressed nasal tip, large earlobes, a cleft or high-arched palate, scoliosis, short fifth finger, persistence of fingerpads, radiographic abnormalities of the vertebrae, hands, and hip joints, and recurrent otitis media in infancy; also known as Niikawa-Kuroki syndrome. 

===Kahler's disease===
Multiple myeloma. 

===Kallmann's syndrome===
Anosmia and hypogonadotropic hypogonadism stemming from failure of LHRH-expressing neurons to migrate. 

===Kanavel's sign===
Four signs of tenosynovitis: 1. affected finger held in slight flexion; 2. pain over volar aspect of affected finger tendon upon palpation; 3. swelling of affected finger; 4. pain on passive extension of affected finger. 

===Kandinsky-Clerambault's syndrome===
Alienation from or loss of one's own mental processes which are attributed to somebody else, combined with delusions of external influences, such as stealing or insertion of thoughts, described independently by Russian psychiatrist Victor Khrisanfovich Kandinsky (1849–1889) and French psychiatrist Gaëtan Gatian de Clerambault (1872–1934) . 

===Kaplan-Meier curve===
Curve that estimates the probability of survival of a defined group at a designated time interval (conditional probability) based on a non-parametric survival function. 

===Kaposi's sarcoma===
Low-grade vascular tumor associated with HHV-8, four forms, classic (older men of Mediterranean or Jewish extraction), African, organ transplant-associated, and AIDS; differential for skin lesions includes bacillary angiomatosis from Bartonella. 

===Kartagener's syndrome===
A triad of sinusitis, bronchiectasis, and situs inversus; also associated with ciliary dysfunction. Associated with mutation in DNAI1 and DNAH5, which encode proteins in dynein arm. Described by Manes Kartagener, Swiss physician, 1897-1975. 

===Kasabach-Merritt syndrome===
Capillary hemangioma or hemangioendothelioma associated with thrombocytopenic purpura and extensive and progressively enlarging vascular malformations which may involve large portions of their extremities; bleeding commonly develops in the first year of life, secondary to chronic DIC triggered by stagnant blood flow through the tortuous abnormal vessels; anemia caused by red cell damage as blood passes through deformed vessels of the tumor. 

===Kasai procedure===
For treating biliary atresia, hepatoportoenterostomy, with biliary drainage created from small intestine. 

===Kashin-Beck disease===
Deforming arthritis associated with selenium deficiency, identified in an area of China and Tibet where soil is extremely low in selenium; iodine deficiency risk factor. 

===Katayama fever===
Acute schistosomiasis, after Katayama valley in Japan where S. japonicum endemic; seen in travelers but not in native people because of exposure in utero. Symptoms of prostration, fever, sweats, myalgia, and diarrhea. 

===Kawasaki's disease===
Acute febrile illness of infants and children, characterized by cutaneous and mucosal erythema and edema with subsequent desquamation, cervical lymphadenitis, and complicated by coronary artery aneurysms (20%); associated with antiendothelial antibodies. 

===Kayser-Fleischer rings===
A greenish yellow pigmented ring encircling the cornea just within the corneoscleral margin, seen in hepatolenticular degeneration, due to copper deposited in Desçemet's membrane (posterior limiting layer of cornea); seen in Wilson's disease (with neurologic involvement) and other cholestatic hepatic diseases. 

===Kearns-Sayre syndrome===
A mitochondrial disease with progressive ophthalmoplegia, retinal pigmentation degeneration, heart block; caused by various mitochondrial DNA mutations. 

===Kegel exercises===
Exercises for strengthening pelvic muscles in order to increase urethral closure mechanism in urinary incontinence. 

===Kehr's sign===
Pain in the left shoulder associated with splenic rupture. 

===Kell blood group system===
Red blood cell antigen, named after Mrs. Kelleher, pregnant woman in whom anti-K was discovered by Coombs in 1946; function of antigens in this system are unknown. 

===Kellgren's arthritis===
Severe form of primary osteoarthritis, erosive osteoarthritis, associated with severe osteoporosis of hands. 

===Kelly's sign===
Visible peristalsis of the ureter in response to squeezing or retraction; used to identify the ureter during surgery. 

===Kennedy syndrome===
X-linked spinobulbar muscular atrophy; from CAG repeat expansion encoding androgen receptor; leads to distal limb amyotrophy, bulbar signs, fasiculations prominent, androgen insensitivity with gynecomastia, testicular atrophy, and oligospermia. 

===Kenny-Caffey syndrome===
Skeletal disorder with osteosclerosis and recurrent bacterial infections. Associated with mutation in tubulin-specific chaperone E. Mutation in same gene associated with Sanjad-Sakati syndrome. 

===Kent, bundle of===
AV bypass accessory tract in Wolff-Parkinson-White syndrome that directly connects atrial and ventricular myocardium. 

===Kerandel's hyperesthesia===
In African trypanosomiasis, excruciating pain after minor soft-tissue injury, e.g. in palms and ulnar region. 

===Kerckring's valves===
Plicae circulares, found in lining of small intestine. 

===Kerley A lines===
In pulmonary edema, thin nonbranching lines several inches in length, radiating from hila, and not following the course of vessels or airways, attributed to thickening of connective tissue sheets which contain communicating perivenous and bronchoarterial lymphatics. 

===Kerley B lines===
In pulmonary edema, transverse lines 1-3 cm in length and 1-2 mm in width, arranged in a horizontal stepladder pattern, 0.5-1 cm apart along the lower lateral lung margins, extending to the pleura; lines visible in this area because pulmonary lobules are well-developed in this area and lines reflect thickening of, or fluid in, lymphatic vessels in interlobular septa; also seen in lymphangitic spread of malignancies. 

===Kerley C lines===
In pulmonary edema, fine interlacing lines throughout the lung base producing a spider web appearance; controversial if unique lines v. crossing lines. 

===Kernig sign===
In meningeal irritation (as in meningitis), flexion of patient's leg at both hip and knee and then straightening of knee associated with pain and increased resistance to extending knee. 

===Kernohan notch===
Focal impression against the cerebral peduncle; pressure against notch seen in uncal herniation. 

===Kerr incision===
Low transverse uterine incision for caesarian section. 

===Keshan disease===
Endemic cardiomyopathy in China associated with selenium deficiency. 

===Keutel syndrome===
Malformation syndrome characterized by multiple pulmonary stenoses, neural hearing loss, short terminal phalanges, and calcifications and/or ossification of the cartilage in ears, nose larynx, trachea, and ribs; due to mutation in gene encoding human matrix Gla protein. 

===Kew Gardens spotted fever===
Rickettsialpox due to Rickettsia akari, from Kew Gardens, New York. 

===Kidd blood group system===
Named after Mrs. Kidd, pregnant woman in whom anti-Jka was discovered by Allen in 1951; antigens in this system are located on a red cell urea transporter. 

===Kienböck disease===
Osteonecrosis of the carpal lunate that most commonly affects men between ages 20-40; sometimes history of trauma; may lead to end-stage arthritis of wrist with progression. 

===Kiesselbach's plexus===
Vascular plexus on the anterior nasal septum, bleeding from this plexus associated with most common form of epistaxis. 

===Kikuchi's disease===
Histiocytic necrotizing lymphadenitis, characterized by cervical lymphadenopathy with tenderness, fever, and night sweats; tends to occur in young women; histology can be confused with lymphoma. 

===Killian-Jamieson area===
Region between oblique and transvere fibers of the cricopharyngeus muscle; potential area for muscular dehisence and Zenker's diverticulum. 

===Killip class===
Described in 1967, in myocardial infarction, class I, no heart failure, 0.5% mortality; class II, S3 and/or basal lung crepitations, 2.2% mortality; class III, acute pulmonary edema, 19.2% mortality; class IV, cardiogenic shock, 61.3% mortality (mortality rates current). 

===Kimmelstiel-Wilson disease===
Intercapillary glomerulosclerosis from diabetes; lesion is PAS-positive material deposited at periphery of glomerular tufts. 

===Kimura's disease===
Chronic inflammatory condition with large subcutaneous masses on head or neck of Asian males associated with eosinophilia. 

===Kinsbourne syndrome===
Opsoclonus myoclonus, a rare movement disorder, associated with neuroblastoma and felt to be autoimmune in origin. 

===Klatskin tumors===
Tumors arising from the part of the common bile duct between the cystic duct junction and the confluence of the right and left hepatic ducts at the liver hilus; notable for their slow growing behavior, marked sclerosing characteristics, and the infrequent occurrence of distal metastases. 

===Kleihauer-Betke test===
Testing for the presence of fetal blood cells in maternal circulation. 

===Kleine-Levin syndrome===
A rare form of periodic hypersomnia, occurring in males aged 10 to 25 years, characterized by periods of ravenous binge eating alternating with prolonged sleep (as long as 18 hours), along with behavioral disturbances, impaired thought processes, and hallucinations; acute illness or fatigue may precede an episode, which may occur as often as several times a year; thought to be a disorder of hypothalamically mediated satiety. 

===Klein-Waardenburg syndrome===
See Waardenburg's syndrome type III. 

===Klinefelter syndrome===
XXY, first described in 1942 as constellation of enlarged breasts, sparse facial and body hair, small testes, long bone abnormality, and an inability to produce sperm; occurs in 1/500 to 1/1000 births. 

===Klinger disease===
Wegener's granulomatosis; first described by Heinz Klinger in 1931 as a medical student and then described by Friederic Wegener in 1936. 

===Klippel-Feil syndrome===
Congenital fusion of two or more cervical vertebrae, producing a low posterior hairline, decreased movement, and a short neck that displaces the head anteriorly and inferiorly. 

===Klippel-Trenaunay syndrome===
Congenital condition characterized by port-wine stain (cutaneous capillary hemangiomas), soft tissue and bony hypertrophy, and venous malformations and lymphatic abnormalities, usually limited to one limb. 

===Klippel-Trenaunay-Weber syndrome===
Association of Klippel-Trenaunay syndrome with AV fistula; affects Casey Martin, golfer in disability case brought to U.S. Supreme Court 2001 against PGA. 

===Klumpke's palsy===
Lower plexus palsy affecting C8-T1 nerve roots; may occur during birth trauma. 

===Klüver-Bucy syndrome===
Behavioral disorder from bilateral temporal lobe dysfunction, characterized by a flattening of emotions, increased oral tendencies, hypersexuality, compulsive tendency to react to every object, failed to recognize familiar objects. Observed in 1937 following experimental bilateral removal of temporal lobe (including amygdala and hippocampal formation) in monkeys. 

===Kniest dysplasia===
Autosomal dominant metatropic dwarfism associated with mutation in COL2A1. 

===Kobberling's syndrome===
Familial partial lipodystrophy affecting adipose tissue in extremities and normal adipose tissue elsewhere. 

===Kocher's incision===
Right subcostal incision for open cholecystectomy. 

===Kocher's maneuver===
Dissection of the duodenum from the right-sided peritoneal attachment to allow mobilization and visualization of the back of the duodenum and pancreas. 

===Kocher's maneuver===
For closed reduction of anterior shoulder dislocation, traction to the elbow with external rotation of the humerus and adduction of elbow towards chest; however not generally recommended because of association with neurovascular complications and proximal humerus fractures. 

===Kocher's test===
Compression of lateral lobes of thyroid causing stridor; associated with thyroid carcinoma, goiter, or thyroiditis. 

===Koch's bacillus===
Tuberculosis bacillus. 

===Koch's postulates===
Criteria for linking a specific microorganism to a disease 1. organism must be found in lesion of disease; 2. organism can be isolated in single colonies on a single medium; 3. inoculation of culture causes lesion in experimental animals; 4. organism can be recovered from lesions in these animals. 

===Koebner's phenomenon===
Referring to physical trauma (rubbing or scratching) as a major factor in eliciting psoriasis lesions; also depigmented, sharply demarcated papules in vitiligo following minor trauma; may also be seen in lichen planus. 

===Koeppe's nodules===
Projections into the pupil seen in sarcoidosis, tuberculosis, and other uveitides. 

===Köhler's disease===
Aseptic necrosis or osteochondrosis of the navicular bone. 

===Kohn, pores of===
Connections between lung alveoli. 

===Kojewnikoff syndrome===
Epilepsia partialis continua (simple partial status epilepticus). 

===Kommerell diverticulum===
Anomaly where left subclavian artery arises from this diverticulum on the aortic arch as the 4th branch and passes behind the esophagus to the left arm; can be rarely associated with dysphagia. 

===Koplik's spots===
Small, white spots (often on an reddened background) that occur on the inside of the cheeks early in the course of measles; considered to be pathognomonic exanthem in measles. See also Fordyce's spots. 

===Korotkoff sounds===
Sounds heard in between systolic and diastolic pressure; origin related to the spurt of blood passing under the cuff and meeting a static column of blood; I, first appearance of low-frequency tapping sounds; II, softer and longer sounds; III, crisper and louder sounds; IV, muffled and softer sounds; V, complete disappearance of sounds. 

===Korsakoff's syndrome===
From thiamine deficiency accompanying alcoholism: profound memory loss, mammillary bodies as well as portions of medial thalamus believed to be destroyed. 

===Kostmann syndrome===
Severe congenital neutropenia, associated with mutation in ELA2 (elastase). Characterized typically by a granulopoeisis impairment at the promyelocyte stage; risk of evolution to MDS or AML, responds to G-CSF. 

===Kounis syndrome===
Allergic or hypersensitivity reaction associated with acute coronary syndrome. 

===Krabbe's disease===
Autosomal recessive sphingolipidosis (sulfatidose), from beta-galactosidase deficiency, resulting in increased galactocerebrosides, mental retardation, blindness, deafness, paralysis, convulsions, total absence of myelin, globoid bodies in white matter of brain, fatal in early life. 

===Kraissl's lines===
Lines of skin tension, defined in living individuals (and e.g. correlate with wrinkle lines in face). Wounds made parallel to Kraissl's line are felt to heal better. See also Langer's lines. Described by Kraissl in 1951 (Plast Reconst Surg 8:1). 

===Krause's end-bulbs===
Sensory receptors for cold. 

===Krebs cycle===
Citric acid cycle or tricarboxylic acid cycle; central metabolic pathway that takes place in mitochondria involved in catabolism of carbohydrates and fat and generation of ATP; after Sir Krebs who proposed pathway in 1937. 

===Krukenberg's tumor===
Ovarian metastasis of stomach cancer; characterized by signet ring cancer cells. May also seen in malignancies from colon, breast, and other mucin-gland organs. 

===Kübler-Ross dying stages===
(1) Denial and isolation, (2) anger, (3) bargaining, (4) depression, (5) acceptance; described in 1969 by Elisabeth Kübler-Ross. 

===Kufs disease===
Adult neuronal ceroid lipofuscinosis, CLN4. 

===Kugelberg-Welander disease===
See under Wohlfart-Kugelberg-Welander disease. 

===Kulchitsky's cells===
Neuroendocrine argentaffin cells present along the bronchial epithelium, particularly in the fetus and neonate; small cell carcinoma has granules similar to Kulchitsky's cells; felt to be origin of carcinoid tumors. 

===Kupffer cells===
Phagocytic cells of the mononuclear phagocyte series found on the luminal surface of endothelial cells in hepatic sinusoids; they metabolize old red blood cells, digest hemoglobin. 

===Kussmaul-Maier disease===
Former name for polyarteritis nodosa. 

===Kussmaul's respiration===
Hyperpnea, associated with acidosis, especially diabetic ketoacidosis, but may also be seen in uremia. 

===Kussmaul's sign===
Jugular vein distension during inspiration (reversal of normal pattern of decreasing jugular venous pressure during inspiration); classically seen in constrictive pericarditis because of normal increase in venous return with increased abdominal pressure from diaphragmatic contraction leading to increase in right atrial pressure from non-complaint right ventricle. Most common contemporary cause is severe right-sided heart failure (JAMA 1996: 275:632). Sign absent generally in cardiac tamponade. 

===Kveim antigen===
Saline suspension of human sarcoid tissue prepared from spleen (or liver or lymph node) of an individual with active sarcoidosis; used in Kveim-Sitzbach test. 

===Kveim-Siltzbach test===
An intradermal test for the detection of sarcoidosis, done by injecting Kveim antigen and examining skin biopsies after 3 and 6 weeks; positive test, a noncaseating granulomatous reaction; sensitivity 35-88%, specificity 75-99% Morton A. Kveim, Norwegian dermatologist, born 1892. 

===Kyrle disease===
Chronic generalized dermatosis, formation of large papules with central keratin plugs; associated with diabetes mellitus and renal failure. 

==L==

===La Crosse encephalitis===
Transmitted by tree hole mosquito, Aedes trisereiatus and causes most common arboviral infection in children in N. America; hyponatremia and fever associated with worse outcome. Discovered in La Crosse, Wisconsin in 1963. 

===Lachman maneuver===
For diagnosing anterior cruciate ligament tear, pull on tibia in anterior direction with knee flexed at 20-25 degrees (if tibia slides anteriorly &gt;2 mm, positive). 

===Ladin's sign===
A sign of pregnancy, an area of elasticity on the anterior face of the uterus just above the cervix; felt on palpation through the vagina as early as the 5th or 6th week of pregnancy. 

===Lady Windermere syndrome===
Mycobacterium avium complex pulmonary disease described in fastidious elderly women in the dependent portion of the lingula or the right middle lobe due to proposed habitual voluntary suppression of cough leading to the development of nonspecific inflammatory processes in these poorly draining lung regions. Chest 1992;101:1605-9. 

===Laennec's cirrhosis===
In alcoholic cirrhosis, residual parenchymal nodules that protrude like "hobnails" from the surface of the liver. 

===Lafora's disease===
Progressive myoclonus epilepsy, autosomal recessive, onset teenage years, characterized by seizures and cumulative neurological deterioration, death usually within ten years of first symptoms; associated with intracellular inclusions (Lafora bodies); associated with mutation in gene EPM2A. 

===Laimer triangle===
Area defined by cricopharyngeus muscle and esophageal muscles. 

===Laki-Lorand factor===
Factor XIII. 

===Lambert, canals of===
Direct accessory bronchioalveolar connections. 

===Lambert-Eaton myasthenic syndrome===
Disease of neuromuscular junction associated with paraneoplastic process with proximal muscle weakness that improves with repetitive stimulation; associated with P/Q type presynaptic voltage-gated calcium channel antibodies; 70% have malignancy, usually small cell cancer. 

===Lambl's excrescences===
Small filiform or lamellar lesions on aortic valve leaflets, first described in 1856 . 

===Lance-Adams syndrome===
Post hypoxic monoclonus. 

===Lancisi's sign===
Giant V waves in tricuspid regurgitation. 

===Landau-Kleffner syndrome===
Acquired epileptic aphasia; childhood disorder characterized by auditory verbal agnosia, aphasia, and seizures. 

===Landolfi's sign===
In aortic regurgitation, systolic contraction and diastolic dilation of the pupil. 

===Landsteiner-Weiner blood group system===
After Landsteiner and Weiner who discovered this antigen system; injected Rhesus monkey red blood cells into guinea pigs producing an antibody thought to recognize the antigen D described by Levine in 1939. Later discovered that these antibodies did not recognize D but rather an antigen that is strongly expressed on Rh positive red cells and weakly expressed on Rh negative red blood cells; antigens located on an intercellular adhesion molecule for CD11/CD18. 

===Lane-Hamilton syndrome===
Association between idiopathic pulmonary hemosiderosis and celiac disease. 

===Langerhans cell===
Member of class of bone marrow-derived dendritic cells; antigen-presenting cell; differs from other histiocytes by being CD1a-positive. 

===Langerhans cell histiocytosis===
Encompasses histiocytosis-X, eosinophilic granuloma, Letterer-Siwe disease, and Hand-Schüller-Christian triad. 

===Langerhans granules===
See Birbeck granules. 

===Langer's lines===
Lines used for elective incisions, developed by Karl Langer, an anatomy professor, from cadavers in rigor mortis. Incisions made parallel to Langer's lines felt to heal better with less scarring. Believed to lie parallel to collagen fibers. By contrast, see Kraissl's lines. 

===Laplace's law===
Wall tension = pressure x radius. Explains colon perforation preferentially at the cecum because of the increased radius and resultant increased wall tension. 

===Laron dwarfism===
Autosomal recessive, dwarfism from growth hormone receptor defect leading to failure to produce IGF-1. 

===Lasègue's sign===
In lumbar root or sciatic nerve irritation, when patient is supine with hip flexed, dorsiflexion of ankle causing pain or muscle spasm in the posterior thigh. 

===Lassa fever===
Hemorrhagic fever caused by Lassa virus, first isolated in 1969 in Lassa, Nigeria, an arenavirus, spread through contact with secretions (e.g., urine) from infected rats; fatality 15-20% of hospitalized patients; can be treated with ribavirin. 

===Laterjet, nerve of===
Branch of vagus nerve thought to carry nerves specifically to antrum of stomach. 

===Launois-Bensaude syndrome===
See Madelung's disease. 

===Laurence-Moon syndrome===
Mental retardation, pigmentary retinopathy, hypogenitalism, and spastic paraplegia; distinct from Bardet-Biedl syndrome. 

===Lawrence-Seip syndrome===
Two forms: congenital lipodystrophy and acquired generalized lipodystrophy; general disappearance after birth (generally during childhood and may occur following infections); associated with acanthosis nigricans, excess body hair, enlargement of genitalia, diabetes. 

===Leber hereditary optic neuropathy===
Mitochondrial DNA disease, progressive bilateral loss of central vision, presents 15-35 y.o, associated with cardiac conduction defects and minor neurological manifestations. 

===Leeuwenhoek syndrome===
Respiratory myoclonus characterized by intermittent fits of involuntary spasms of the diaphragm and accessory muscles of respiration. Differentiated from hiccups because in hiccups the glottis is closed, while in respiratory myoclonus it is open causing air to rush in with each diaphragmatic contraction. Described by the microscopist Leeuwenhoek in 1723. 

===LeFort I fracture===
Transverse maxillary fracture above dental apices, which also traverses pterygoid plate; nasal complex stable. 

===LeFort II fracture===
Fracture through frontal process of maxilla, through orbital floor, and pterygoid plate; midface is mobile. 

===LeFort III fracture===
Complete craniofacial separation; different from LeFort II in that it extends through the nasofrontal suture and frontozygomatic sutures. 

===Legg-Calvé-Perthes disease===
Self-limiting hip disorder of children, 4-8 y.o. (M:F 8:1) involving vascular compromise of the capital femoral epiphysis and leading to aseptic necrosis. Also can affect small dogs. 

===Legionnaire's disease===
Pneumonia caused by Legionella species, aerobic gram-negative bacilli that do not grow on routine bacteriologic media; first identified in 1976 during outbreak at American Legion Convention in Philadelphia. 

===Legius syndrome===
Neurofibromatosis type 1-like syndrome, from autosomal dominant mutation in SPRED1, associated with café-au-lait macules, axillary freckling, and macrocephaly. Not associated with peripheral or central nervous system tumors typical of NF1. 

===Leigh's disease===
Autosomal recessive disorder from defects in mitochondrial pathway for converting pyruvate to ATP, leading to lactic acidemia, developmental problems, seizures, involvement of periaqueductal gray area, extraocular palsies, weakness, hypotonia, death within 1 to 2 years. 

===Leiner's disease===
Seborrheic erythroderma associated with diarrhea and failure to thrive and to generate C5a chemotactic factor. 

===Lemierre's syndrome===
Oropharyngeal infection (usually by anaerobe Fusobacterium necrophorum) complicated by internal jugular vein thrombosis and metastatic abscesses in lung, characterized by spiking fevers, tenderness of sternocleidomastoids. See ring enhancement with central lucency in internal jugular vein on CT. 

===Lenègre's disease===
Sclerodegenerative disease of conduction system, particularly of right bundle branch and left anterior fasicle in people over 50; associated with slow progression to complete heart block. Also known as Lev's disease. 

===Lenk's triad===
In retroperitoneal hemorrhage, flank pain, a palpable tender mass, and signs of internal bleeding (e.g. hematuria). 

===Lennox-Gastaut syndrome===
Childhood seizure disorder associated with multiple seizure types (including drop attacks, atypical absences general tonic clonic seizures, and myoclonus), slow generalized spike-and-slow-wave EEG, mental retardation, and resistant to standard anti-epileptic medications. 

===Leopold's maneuver===
At 28 weeks, four sequential palpations of gravid abdomen to determine the position of the fetus. 

===leprechaunism===
1 in 4 million births, associated with elfin-like facies, decreased subcutaneous. adipose tissue, acanthosis nigricans, and growth retardation, failure to thrive, and early death, insulin resistance. From defect in insulin receptor. Also known as Donohue syndrome. 

===Leriche's syndrome===
Aortoiliac occlusive disease producing distal ischemic symptoms and signs, e.g. pulseless femoral artery: (1) claudication of buttocks, (2) impotence, (3) atrophy of buttocks (seen with iliac occlusive disease). 

===Leri-Weill syndrome===
Dyschondrosteosis; a short stature syndrome characterized by mesomelic shortening of the forearms and lower legs and by bilateral Madelung deformity of the wrists. 

===Lesch-Nyhan syndrome===
X-linked disorder leading to absence of hypoxanthine guanine phosphoribosyl transferase (HGPRT, involved in salvage pathway in purine synthesis), associated with hyperuricemia, severe neurologic deficits with mental retardation, self-mutilation, and in some cases gouty arthritis. 

===Leser-Trélat sign===
Sudden appearance and rapid increase in the number and size of seborrheic keratoses with pruritus; associated with internal malignancy. 

===Letterer-Siwe disease===
Acute disseminated Langerhans cell histocytosis; associated with development of cutaneous lesions that resemble a seborrheic eruption secondary to infiltrations of Langerhans' histiocytes over the front and back of the trunk and on the scalp; concurrent hepatosplenomegaly, lymphadenopathy, pulmonary lesions, and eventually destructive osteolytic bone lesions. 

===LeVeen shunt===
For treating refractory ascites, peritoneovenous shunt connecting peritoneum and central venous system, compare with Denver shunt; LeVeen shunt uses disc valve in firm polypropylene casing. 

===Levine's sign===
When describing angina, use of clenched fist over sternum; described by Samuel A. Levine, U.S. cardiologist, 1891-1966. Levine sign itself 14% sensitive for cardiac pain (BMJ 1995;311:1660). 

===Levinthal paradox===
Magnitude of conformational search problem in protein folding; an unbiased search for all possible protein conformations would take a lifetime, yet proteins fold in microseconds to minutes. 

===Lev's disease===
Complete heart block from fibrosis or calcification extending from cardiac fibrous structures into the conduction system. Also known as Lenègre's disease. 

===Lewis blood group system===
Named after Mrs. Lewis, pregnant woman in whom anti-Lea was discovered by Mourant in 1946; function of antigens in this system are unknown. 

===Lewy bodies===
Eosinophilic intracytoplasmic bodies of alpha synuclein in neurons of substantia nigra and locus ceruleus present in Parkinson's disease. 

===Lewy body dementia===
Most common dementia associated with Parkinson's disease characterized by Lewy bodies found in brain stem and cortex. Visual hallucinations may be exacerbated by the treatment for parkinsonism. 

===Leydig cell tumors===
Testicular tumor derived from the stroma, may find Reinke crystals. 

===Lhermitte-Duclos disease===
Dysplastic cerebellar gangliocytoma; associated with germ line PTEN mutations; felt to be a part of multiple hamartoma syndrome or Cowden's syndrome. 

===Lhermitte's sign===
Sudden electric-like shocks extending down the spine on flexing the head; may result from posterior column lesion, toxic effects of radiation. Seen in 3% of multiple sclerosis. Also may be found in vitamin B6 toxicity, vitamin B12 deficiency. 

===Libman-Sacks disease===
In systemic lupus erythematosus, intense mitral and tricuspid valvulitis with development of small, sterile vegetations. 

===Lichtenberg's figures===
Branching pattern of cutaneous marks pathognomonic for lightning injury. 

===Liddle's syndrome===
Severe low renin hypertension, hypokalemia, and metabolic alkalosis that mimics hyperaldosteronism but found to have low aldosterone levels; due to constitutively activating autosomal dominant mutation in beta subunit of epithelial sodium channel. 

===Lieberkühn, crypts of===
Intestinal glands found between villi. 

===Li-Fraumeni syndrome===
Cancer predisposition syndrome from mutant p53 allele, predisposition toward breast carcinomas, sarcomas, leukemia, brain tumors, and adrenocortical carcinoma; half have tumors before age 30, 70% before age 90. Autosomal dominant. 

===Light's criteria===
For distinguishing transudate v. exudate in pleural fluid: if at least one of the criteria is present, fluid virtually always an exudate: (1) pleural fluid/serum protein ratio &gt; 0.5; (2) pleural fluid LDH/serum LDH ratio &gt; 0.6; (3) pleural fluid LDH &gt; 2/3 upper limit of normal serum LDH. Ann Intern Med 1972; 77:507. 

===Likoff's syndrome===
In young women (30s-50s), presence of chest pain with abnormal EKG but with normal coronary angiograms (N Engl J Med1967;276:1063). 

===Linton test===
Modification of Perthes test, elevation of leg with patient supine and tourniquet in place; if veins fail to drain, implies venous obstruction. 

===Lipschultz ulcer===
Vulvar ulcer. 

===Lisch nodules===
In type I neurofibromatosis, pigmented iris hamartomas. 

===Lisfranc fracture===
Fracture and dislocation involving the joints of the midfoot. Named after French surgeon Jacques Lisfranc de St. Martin, in Napoleon's army, for the amputation at this location. 

===Lisfranc joint===
Joint located just above the arch of the foot, between the tarsal and metatarsal bones. 

===Lisker's sign===
In thrombophlebitis or deep vein thrombosis, tenderness to percussion of the medial anterior tibial surface. 

===Lissauer's tract===
Small diameter primary sensory axons (presumably mediating pain and temperature senses) on their way into the dorsal horn. 

===Litten's sign===
Diaphragmatic movement seen on one side but not the other side in unilateral phrenic nerve palsy. 

===Little's disease===
Cerebral palsy; specifically congenital spastic diplegia; described by English surgeon Little in 1843. 

===Littre's hernia===
Hernia involving a Meckel's diverticulum. Compare with Amyand's hernia, De Garengoet's hernia. 

===Lloyd's sign===
In pyelonephritis or renal stone, percussion over loin eliciting tenderness. 

===Loeys-Dietz syndrome===
Classic triad of craniofacial abnormalities, aortic aneurysm, and bifid uvula; autosomal dominant syndrome associated with high risk for aortic dissection at an early age; due to mutation in TGFBR1 (type 1) or TGFBR2 (type 2); see also Marfan syndrome. 

===Löffler's cardiomyopathy===
A form of restrictive cardiomyopathy, associated with eosinophilia; endocarditis parietalis fibroplastica. 

===Löffler's syndrome===
Simple pulmonary eosinophilia, characterized by transient pulmonary lesions, eosinophilia in the blood, and a benign clinical course. Lungs show alveoli with thickened septa from infiltrate composed of eosinophils and occasional interspersed giant cells, but no vasculitis, fibrosis, or necrosis. Associated with ascaris and strongyloides. 

===Löfgren's syndrome===
Sarcoidosis associated with triad of erythema nodosum, bilateral hilar adenopathy, and polyarthritis; 10-15% of sarcoidosis present this way. 

===Looser's zones===
In osteomalacia, radiolucent narrow lines that lie either at right angles or obliquely to the cortical outlines of bones and often transect them; bilateral and symmetric, found at the axillary margins of the scapula, lower ribs, neck of the proximal femurs, and posterior regions of the proximal ulnas; related either to stress fractures or to mechanical erosion by penetrating nutrient arteries; also known as Milkman's fractures. 

===Lorenzo's oil===
After Lorenzo Odone, diagnosed with adrenoleukodystrophy in 1984, a formulation of triglycerides of monounsaturated oleic acid and erucic acid 4:1, felt to reduce very long chain fatty acids to normal levels in ALD. 

===Lou Gehrig's disease===
Amyotrophic lateral sclerosis (in France, known as Charcot's disease). 

===Louis, angle of===
Sternal angle. 

===Louvel's sign===
In deep vein thrombosis, venous pain induced by coughing, prevented by pressing over proximal end of vein. 

===Lovibond's angle===
The angle made by the proximal nail fold and the nail plate. 

===Lowenberg's sign===
In deep vein thrombosis, two calves are wrapped with cuffs to see if there is asymetry in tolerance to pressure of 180 mm Hg. 

===Löwenstein-Jensen's medium===
For growing out M. tuberculosis; contains malachite green, a triphenlyamine die like crystal violent, inhibits growth of unwanted organisms during 6 week incubation period as well as complex nutrients. 

===Lowe's syndrome===
X-linked, oculocerebrorenal syndrome characterized by congenital cataracts, mental retardation, renal tubular acidosis type 2; from defect in lipid phosphatase, phosphatidylinositol 4,5 bisphosphate [PtdIns(4,5)P2]5-phosphatase, which localizes to the Golgi apparatus and is suspected to play a role in Golgi vesicular transport. 

===Lown-Ganong-Levine syndrome===
Cardiac preexcitation syndrome with enhanced AV node pathways, &lt;0.12 s, no QRS widening, no delta waves. 

===Ludwig's angina===
Aggressive infectious process of the submandibular, sublingual, and submental fascial spaces frequently occurring as a result of infection from 2nd and 3rd lower molar; 54% mortality in preantibiotic era, now 4%. Described in 1836 by Wilhelm Frederick von Ludwig. 

===Lugol's solution===
5% iodine and 10% KI, a dose of 6.3 mg of I per drop, for giving iodine. 

===Lundberg A wave===
In ICP monitoring, waves that have a duration of 5-20 minutes and an amplitude of 50 mm Hg over the baseline ICP, after which ICP is reset to a higher baseline level; sign of severely compromised intracranial compliance and can result in significant decrease in cerebral perfusion pressure and herniation. 

===Lund's node===
Lymph node found in Calot's triangle, aka Calot's node. 

===Luria's law===
Three antibiotics = 1 fungal infection. 

===Luschka, ducts of===
Small tubular channels found buried within the gallbladder wall adjacent to the liver, communicates with the biliary tree; rarely patent accessory bile secretory ducts. 

===Luschka, foramina of===
Two laterally placed foramens exiting out of fourth ventricle of the brain. 

===Lutembacher's syndrome===
Atrial septal defect with mitral stenosis. Congenital condition, though mitral stenosis may be acquired from rheumatic fever. 

===Lutheran blood group system===
Named after Mrs. Luteran, pregnant woman in whom anti-Lua was discovered by Cutbush in 1945; Cutbush assumed that the name on the sample had been misspelled, hence "Lutheran" instead of "Luteran"; function of antigens in this system unknown. 

===Lyell's syndrome===
Toxic epidermal necrolysis. 

===Lyme disease===
Inflammatory disease caused by spirochete Borrelia burgdorferi, spread by Ixodes tick, characterized by early local disease with erythema migrans, myalgias, followed by early disseminated disease with carditis, neurologic findings (lymphocytic meningitis, cranial nerve palsies, also see Bannwarth's syndrome), and late disease characterized by arthralgias and arthritis. Full syndrome recognized as Lyme diseased based on patients identified in Lyme, CT in 1975. 

===Lynch syndrome I===
Cancer family syndrome with multiple colon cancers 2 to 3 decades earlier, predilection for proximal colon; Lynch syndromes most common forms of familial colon cancer, 5-10% of all cases of colon cancer; better prognosis than sporadic colon cancer. Due to deficiency in mismatch repair genes in 85% of Lynch syndromes; autosomal dominant. 

===Lynch syndrome II===
Cancer family syndrome, all features of Lynch I with early onset of carcinoma at other sites including endometrium, ovaries, and stomach, also upper tract TCC. 

===Lyon hypothesis===
Only one of two X chromosomes is genetically active.