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Isolated primary pigmented nodular adrenocortical disease
Isolated primary pigmented nodular adrenocortical disease (i-PPNAD) is a rare autosomal dominant adrenal disorder causing ACTH-independent Cushing syndrome via pigmented cortical micronodules, without Carney complex; PRKAR1A is the leading gene, treated by adrenalectomy.
Isolated proximal femoral focal deficiency
Isolated proximal femoral focal deficiency (PFFD, CPFD, ORPHA:633228) is a rare congenital femur anomaly from failed subtrochanteric femoral development; unilateral in 85–90%, Aitken classes A–D, unknown inheritance, treated by prosthesis, lengthening, or rotationplasty.
Isolated pulmonary artery sling
Isolated pulmonary artery sling (isolated anomalous left pulmonary artery, ORPHA 658574): the left pulmonary artery arises from the right and compresses the trachea, without associated cardiac or airway anomalies; treated by reimplantation.
Isolated pulmonary capillaritis
Isolated pulmonary capillaritis (isolated pauci-immune pulmonary capillaritis, IPIPC, ORPHA:264691) is a rare lung-restricted small vessel vasculitis causing diffuse alveolar hemorrhage without systemic disease, often ANCA-negative, treated with steroids, cyclophosphamide, or rituximab.
Isolated rhombencephalosynapsis
Isolated rhombencephalosynapsis (ORPHA:59315) is a rare cerebellar malformation with fused cerebellar hemispheres and absent or partial vermis, without other major anomalies; about 24% of RES cases, IQ may be normal, hydrocephalus common.
Isolated right ventricular hypoplasia
Isolated right ventricular hypoplasia (IRVH, ORPHA:439, OMIM 277200) is a rare cyanotic congenital heart defect with an underdeveloped right ventricle, normally formed tricuspid and pulmonary valves, and usually a PFO or atrial septal defect causing right-to-left shunt.
Isolated sedoheptulokinase deficiency
Isolated sedoheptulokinase deficiency (SHPK deficiency, OMIM 617213) is an autosomal recessive pentose phosphate pathway disorder causing elevated urinary sedoheptulose and erythritol; its clinical relevance is unclear, with only two isolated cases reported.
Isolated segmental infantile hemangioma
Isolated segmental infantile hemangioma (ORPHA:675380), also called large segmental hemangioma of infancy, is a plaque-like benign vascular tumor covering a developmental area, without PHACE or LUMBAR anomalies, with high ulceration risk.
Isolated splenic vein thrombosis
Isolated splenic vein thrombosis (iSVT) is a clot in the splenic vein without portal or mesenteric involvement, usually from pancreatitis, causing sinistral portal hypertension, gastric varices, and sometimes upper GI bleeding.
Isolated spontaneous cervical artery dissection
Isolated spontaneous cervical artery dissection (CeAD, ORPHA:689001) is a rare non-traumatic tear of a neck artery wall causing false lumen and intramural hematoma; a major stroke cause in adults under 50, treated with antithrombotic therapy.
Isolated systolic hypertension
Isolated systolic hypertension (ISH), ICD-11 BA00.2, is elevated systolic with normal diastolic blood pressure (≥140/<90 mmHg). It dominates hypertension over age 60, reflects arterial stiffening, and treatment lowers major cardiovascular events by about 9%.
Isolated thrombocytopenia
Isolated thrombocytopenia, ICD-11 3B62.2, is a low platelet count (below 150,000/µL) with normal red and white cell lineages and no systemic illness; main causes are ITP and drug-induced thrombocytopenia.
Isolated thyroid-stimulating hormone deficiency
Isolated thyroid-stimulating hormone deficiency, also called isolated TSH or thyrotropin deficiency, is a rare inherited form of central congenital hypothyroidism, apparent in infancy, in which the pituitary cannot synthesize TSH while other pituitary hormones work normally.
Isolated tracheoesophageal fistula
Isolated (H-type, Gross type E) tracheoesophageal fistula: rare congenital trachea-esophagus connection without esophageal atresia, 4-5% of TEFs, causing choking on feeding and recurrent pneumonia; repaired surgically.
Isolated tricuspid valve surgery
Isolated tricuspid valve surgery is an uncommon cardiac operation on the tricuspid valve alone, about 20% of tricuspid surgeries, with roughly 9% operative mortality and higher early mortality than combined procedures.
Isolation Hospitals
An isolation hospital is a hospital or dedicated facility built to treat people with infectious diseases while preventing transmission to others, emerging in nineteenth-century Britain as fever hospitals.
Isometric Contraction
Isometric contraction: muscle tension rises with no change in muscle length or joint angle, as in planks or pushing an immovable object; distinct from isotonic, concentric, and eccentric contractions.
Isometric exercise
Isometric exercise: static muscle contraction against immovable resistance (wall sits, planks, handgrip). Distinguished from dynamic lifting by no joint-angle change; best-evidenced mode for lowering resting blood pressure, highly angle-specific for strength.
Isoniazid preventive therapy
Isoniazid preventive therapy is the administration of isoniazid, usually for 6 to 9 months, to people with latent tuberculosis infection to prevent progression to active TB disease.
Isopropamide
Isopropamide (isopropamide iodide, Darbid) is a long-acting quaternary ammonium antimuscarinic drug, first FDA-approved 1957, used orally for peptic ulcer and GI spasm; now discontinued for humans but retained in veterinary prochlorperazine combinations.
Isosorbide mononitrate
Isosorbide mononitrate (ISMN), also called isosorbide-5-mononitrate, is an organic nitrate vasodilator and the major active metabolite of isosorbide dinitrate, used to prevent angina; ~100% oral bioavailability, ~5-hour half-life, once-daily dosing to avoid nitrate tolerance.
Isosporiasis
Isosporiasis (cystoisosporiasis) is an intestinal infection caused by the coccidian parasite Cystoisospora belli, formerly Isospora belli, spread by fecal-oral ingestion of sporulated oocysts and causing watery diarrhea, severe in HIV/AIDS patients; treated with TMP-SMX.
Isotretinoin
Isotretinoin, formerly Accutane, is an oral retinoid approved by the FDA in 1982 for severe recalcitrant nodular acne; it is highly teratogenic and dispensed only under the iPLEDGE REMS.
Isotretinoin syndrome
Isotretinoin syndrome (isotretinoin embryopathy, retinoic acid embryopathy) is a teratogenic embryofetopathy from first-trimester isotretinoin exposure, causing craniofacial, conotruncal cardiac, thymic, and CNS malformations via neural crest cell injury.
Isoxicam
Isoxicam (Maxicam, W 8495) is a withdrawn oxicam NSAID, a piroxicam analog dosed 200 mg once daily for arthritis, suspended worldwide in October 1985 after fatal Stevens-Johnson syndrome and toxic epidermal necrolysis cases.
ISPD-related limb-girdle muscular dystrophy R20
ISPD-related limb-girdle muscular dystrophy R20 (LGMD R20, formerly LGMD 2U) is a rare autosomal recessive LGMD caused by ISPD/CRPPA mutations, with infantile onset, proximal weakness, high creatine kinase, and variable brain, eye, and cardiac involvement.
ISPEK trial
ISPEK (NCT06792240) is a completed phase 2 randomized open-label trial by ASST Santi Paolo e Carlo, Milan, testing 3 months of ferrous bisglycinate-sodium alginate iron sachets in 84 PKU patients aged 3-25, reporting 46.7% lower blood phenylalanine versus diet alone.
iSPOT-D trial
iSPOT-D (International Study to Predict Optimized Treatment for Depression) was a 2,016-patient open-label randomized trial testing predictors of response to escitalopram, sertraline, and venlafaxine-XR in major depressive disorder.
ISRCTN
ISRCTN is a United Kingdom clinical study registry that assigns unique identifiers to clinical trials, recognized as a primary registry by the World Health Organization and launched in 2000.
Istevir hydrochloride (AI-assisted COVID-19 drug)
Iscartrelvir hydrochloride (盐酸伊司特韦片, trade name 艾普司韦, codes WPV01/WU-04) is an oral SARS-CoV-2 3CLpro inhibitor for adult mild/moderate COVID-19, conditionally approved by China's NMPA in July 2026 as a Class 1 innovative drug, the first AI-assisted original drug approved in China and first DEL-derived approved small molecule.