Nervous and sensory conditions

Intracranial hemorrhage

Intracranial hemorrhage, also called intracerebral or subarachnoid hemorrhage, is bleeding inside the skull. It causes 10-20% of strokes, has 30-40% early mortality, and is treated per the 2022 AHA/ASA guideline.

Intracranial hypotension

Intracranial hypotension, also called spontaneous intracranial hypotension (SIH) or CSF hypovolemia, is low CSF volume from a spinal leak causing orthostatic headache; incidence 3.7/100,000, treated with epidural blood patch or surgery.

Intraspinal epidural abscess

Intraspinal (spinal) epidural abscess, SEA, is a pyogenic infection of the epidural space between dura and vertebral periosteum, mostly Staphylococcus aureus, diagnosed by contrast MRI, treated with surgery plus antibiotics.

Inverted duplicated chromosome 15 syndrome

Inverted duplicated chromosome 15 syndrome, also called idic(15) or inv dup(15), is a rare neurogenetic disorder from a maternally derived supernumerary isodicentric chromosome 15 containing the Prader-Willi/Angelman critical region, causing hypotonia, intellectual disability, autism-like behavior, and epilepsy.

IRICDE study

IRICDE (NCT04786522), University of Bari observational study of irisin levels in 20 Charcot-Marie-Tooth patients; found lower irisin than controls, linked to muscle quality, P1NP, and vitamin D; published Frontiers in Endocrinology 2022.

Iridocorneal endothelial syndrome

Iridocorneal endothelial (ICE) syndrome, also called Chandler syndrome, progressive iris atrophy, or Cogan-Reese syndrome, is a rare unilateral disorder in which abnormal corneal endothelial cells migrate over the angle and iris, causing secondary glaucoma and corneal edema.

Iris atrophy

Degeneration of iris (iris atrophy), especially essential or progressive iris atrophy, a rare unilateral ICE syndrome variant with corectopia, iris holes, synechiae, and secondary glaucoma; ICD-10 H21.26, ICD-11 9A90.1.

Iris melanoma

Iris melanoma, a malignant melanocytic tumor of the iris and the most common primary iris neoplasm, about 2–5% of uveal melanomas; spindle-cell, low metastasis rate (3% at 5 years), treated by observation, resection, plaque radiotherapy, or enucleation.

IRVAN syndrome

IRVAN syndrome (idiopathic retinal vasculitis, aneurysms, and neuroretinitis; ORPHA:209943) is a rare retinal vasculopathy of young adults, defined by arterial aneurysms at bifurcations, vasculitis, and neuroretinitis, treated with panretinal photocoagulation and anti-VEGF.

Isolated aniridia

Isolated aniridia (ORPHA:250923, congenital aniridia) is a rare bilateral congenital absence or hypoplasia of the iris without systemic features, caused by heterozygous PAX6 mutations at 11p13, autosomal dominant, with foveal hypoplasia, nystagmus, glaucoma, and poor vision.

Isolated anophthalmia

Isolated anophthalmia: congenital absence of one or both eyes without other eye or systemic anomalies; non-syndromic MAC group, prevalence about 1 in 30,000, caused by SOX2, OTX2, STRA6 variants, chromosomal defects, or environmental exposures.

Isolated cerebellar agenesis

Isolated cerebellar agenesis (ORPHA:1398, ICD-10 Q04.3) is a rare non-syndromic malformation with complete or near-complete absence of the cerebellum, normal-sized posterior fossa, ataxia, dysarthria, and developmental impairment.

Isolated cerebellar vermis hypoplasia

Isolated cerebellar vermis hypoplasia (ORPHA:199630), a rare non-syndromic malformation of the cerebellar vermis; variable outcome from normal development to ataxia, delay, and epilepsy; generally favorable when truly isolated.

Isolated congenital anosmia

Isolated congenital anosmia (ICA, OMIM 107200) is a rare, non-syndromic inability to smell from birth, caused by olfactory bulb defects or epithelial replacement; mostly sporadic, linked to CNGA2 and other genes.

Isolated Dandy-Walker malformation

Isolated Dandy-Walker malformation (ORPHA:217) is a rare non-syndromic posterior fossa brain malformation with hydrocephalus, absent or hypoplastic cerebellar vermis, and a fourth-ventricle cyst; prevalence 1-9/100,000, multigenic inheritance.

Isolated filum lipoma

Isolated filum lipoma (filum terminale lipoma, filar lipoma): benign fat within the filum terminale, separate from the conus. Found in 1.5-4% of spinal MRIs; usually asymptomatic, managed by observation unless tethered cord syndrome develops.

Isolated foveal hypoplasia

Isolated foveal hypoplasia (IFH, ORPHA:519398) is a rare bilateral macular disorder with an underdeveloped foveal pit, absent foveal avascular zone, nystagmus, and low vision, without albinism or aniridia; main genes PAX6, SLC38A8, AHR.

Isolated ocular Stickler syndrome

Isolated ocular Stickler syndrome (ORPHA:209867; OMIM 609508), also called autosomal dominant rhegmatogenous retinal detachment, is a rare non-syndromic vitreoretinopathy with abnormal vitreous, retinal tears, and adult onset, caused mainly by COL2A1 exon 2 variants.

Isolated optic nerve hypoplasia

Isolated optic nerve hypoplasia (ORPHA:637061) is a rare congenital underdevelopment of the optic nerve with subnormal axon numbers, small double-ring optic discs, variable vision, autosomal dominant or recessive inheritance, ICD-10 Q07.8.

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.

ITM2B amyloidosis

ITM2B amyloidosis: autosomal dominant cerebral amyloid angiopathy from ITM2B (BRI2) stop-codon mutations, causing familial British dementia (ABri peptide) and familial Danish dementia (ADan peptide), with dementia, ataxia, and vascular amyloid deposits.

James A. Clifton

James A. Clifton, III (1923–2014) was an American gastroenterologist who led internal medicine at the University of Iowa and whose 1963 research helped create oral rehydration therapy.

Japanese encephalitis (日本脳炎)

Japanese encephalitis (日本脳炎) is a mosquito-borne flavivirus disease of Asia and the western Pacific, spread mainly by Culex tritaeniorhynchus via pigs and birds, causing about 100,000 encephalitis cases yearly; vaccine-preventable, with no antiviral cure.

Jo Cameron

Jo Cameron is a Scottish woman identified in 2019 as the first carrier of FAAH-OUT/FAAH mutation pain insensitivity, feeling virtually no pain, no anxiety or fear, with fast wound healing, affecting roughly one in several million people.

Johnson neuroectodermal syndrome

Johnson neuroectodermal syndrome (Johnson-McMillin syndrome, OMIM 147770) is a rare autosomal dominant disorder with alopecia, anosmia, conductive hearing loss with microtia, and hypogonadotropic hypogonadism; onset in childhood, prevalence under 1 in 1,000,000.

Joubert syndrome

Joubert syndrome (JS, OMIM PS213300), also called Joubert-Boltshauser syndrome, is a rare autosomal recessive ciliopathy defined by the molar tooth sign on brain MRI, hypotonia, ataxia, developmental delay, and over 40 causative ciliary genes.

Juvenile absence epilepsy

Juvenile absence epilepsy (JAE), an idiopathic generalized epilepsy syndrome with adolescent onset of sporadic typical absence seizures, 3–5.5 Hz generalized spike-wave EEG, and generalized tonic-clonic seizures in over 90% of cases.

Juvenile glaucoma

Juvenile glaucoma, also called juvenile open-angle glaucoma (JOAG), is a rare form of primary open-angle glaucoma diagnosed between ages 3 and 40, with very high eye pressure.

Juvenile Huntington disease

Juvenile Huntington disease (JHD), also called juvenile Huntington chorea, is the early-onset form of Huntington disease with symptoms before age 20, usually CAG repeats over 55 in HTT, mostly paternal inheritance, rigid-hypokinetic presentation, seizures, and faster progression than adult-onset HD.