1,527 articles
Infantile-onset X-linked spinal muscular atrophy
Infantile-onset X-linked spinal muscular atrophy (SMAX2, or XL-SMA) is a rare, typically lethal X-linked recessive disorder caused by UBA1 mutations, marked by congenital hypotonia, contractures, and respiratory failure.
Infections of the lacrimal gland
Infections of the lacrimal gland (infectious dacryoadenitis): viral, mainly Epstein-Barr virus, or bacterial, mainly Staphylococcus aureus including MRSA; abscess may need drainage with IV antibiotics.
Infectious anterior uveitis
Infectious anterior uveitis is inflammation of the eye's anterior segment, the iris and adjacent structures, caused by an active infection requiring antimicrobial or antiviral treatment.
Infectious blepharitis
Infectious blepharitis, ICD-11 9A01.3 (感染性眼瞼炎), is bacterial infection of the eyelid margin causing itching, tearing, and lash crusting; spread by contact, endogenous spread, or fomites, and treated with lid hygiene plus antibiotics.
Infectious optic neuropathy
Infectious optic neuropathy (ION): optic nerve damage from viral, bacterial, parasitic, or fungal infection (CMV, syphilis, tuberculosis, Bartonella, fungi), via direct invasion or post-infectious immune injury, requiring antimicrobial versus immunosuppressive decisions.
Infectious panuveitis
Infectious panuveitis is an uncommon eye disease in which viral, bacterial, fungal, or parasitic infection diffusely inflames the entire uveal tract, retina, and vitreous, threatening vision.
Infectious posterior uveitis
Infectious posterior uveitis, also called infectious posterior segment uveitis, is infection-driven inflammation of the retina and choroid (ICD-10 H32.0), caused mainly by Toxoplasma gondii, CMV, herpesviruses, syphilis, and tuberculosis, and treated with antimicrobials before steroids.
Infectious scleritis
Infectious scleritis is microbial infection of the sclera, 5–10% of scleritis cases, usually bacterial (Pseudomonas aeruginosa) after pterygium surgery or trauma; distinct from autoimmune scleritis, needing antimicrobials plus debridement.
Infiltrative optic neuropathy
Infiltrative optic neuropathy (ICD-11 9C40.6) is optic nerve dysfunction caused by cells infiltrating the nerve, most often leukemia, lymphoma, metastases, or granulomatous disease; treated with radiation and intrathecal chemotherapy.
Inflammatory meningitis
Inflammatory meningitis (ICD-11 8E40.2) is meningeal inflammation from an underlying inflammatory disorder, not infection, causing headache, neck stiffness, fever, and photophobia; causes include sarcoidosis, Behçet disease, SLE, Sjögren's, and drugs.
Inflammatory polyneuropathy
Inflammatory polyneuropathy (ICD-10 G61) covers autoimmune peripheral-nerve disorders, chiefly acute Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), treated with IVIg, corticosteroids, plasma exchange, and, since 2024, efgartigimod.
Infrequent episodic tension-type headache
Infrequent episodic tension-type headache (ICHD-3 code 2.1, ICD-11 8A81.0) is a primary headache with bilateral pressing pain on fewer than 1 day per month, lasting 30 minutes to 7 days, without nausea.
Inherited Creutzfeldt-Jakob disease
Inherited Creutzfeldt-Jakob disease (familial or genetic CJD) is a rare autosomal dominant prion disease caused by PRNP mutations, accounting for 10-15% of CJD, with E200K the most common mutation.
Iniencephaly
Iniencephaly (ICD-10 Q00.2) is a rare, usually lethal neural tube defect with occipital bone defect, cervical spina bifida, extreme fixed retroflexion of the head, and apparent absence of the neck, often with anencephaly and other malformations.
Injury of cranial nerves
Injury of cranial nerves: damage to the 12 paired nerves leaving the brain, from trauma, stroke, tumors, or surgery. Classified by Seddon/Sunderland; regenerates about 1-2 mm/day; facial nerve most clinically prominent; synkinesis is a key sequela.
Injury of phrenic nerve
Injury of phrenic nerve (ICD-11 NA44): damage to the C3-C5 nerve supplying the diaphragm, causing diaphragmatic paralysis. Main causes are cardiac and thoracic surgery, cold cardioplegia injury, trauma, tumor, and idiopathic cases.
Injury of trigeminal nerve
Injury of trigeminal nerve (cranial nerve V, ICD-10 S04.3): damage to facial sensory branches, mostly the inferior alveolar and lingual nerves, usually from dental procedures such as third molar extraction, causing numbness or chronic post-traumatic trigeminal neuropathic pain.
Insomnia
Insomnia is a sleep disorder of difficulty falling or staying asleep despite adequate opportunity, chronic at 3+ nights/week for 3+ months, affecting about 10-15% of adults, treated first with CBT-I.
Intellectual disability
Intellectual disability: significant limitations in intellectual functioning and adaptive behavior beginning before age 18 (AAIDD: 22). Formerly "mental retardation"; ICD-11 calls it intellectual developmental disorder. Causes include Down syndrome, FASD; US child prevalence 11-13.4 per 1,000.
Intellectual disability-coarse face-macrocephaly-cerebellar hypotrophy syndrome
Intellectual disability-coarse face-macrocephaly-cerebellar hypotrophy syndrome, also known as SCAR20, is a rare autosomal recessive disorder caused by SNX14 gene mutations, featuring progressive cerebellar ataxia and intellectual disability.
Intellectual disability-seizures-abnormal gait-facial dysmorphism syndrome
Skraban-Deardorff syndrome (SKDEAS), also WDR26-related intellectual disability, a rare autosomal dominant neurodevelopmental disorder from de novo WDR26 variants, causing developmental delay, seizures, abnormal gait, and facial dysmorphism.
Intention tremor
Intention tremor, also called cerebellar tremor, is shaking that appears during target-directed movement and worsens as the limb nears its target, most often from cerebellar dysfunction.
Intercostal neuropathy
Intercostal neuropathy (intercostal neuralgia; ICD-10 G58.0, ICD-11 8C12.0) is peripheral neuropathy of the intercostal nerves causing band-like chest wall pain, mainly after thoracotomy or herpes zoster, treated with blocks, RFA, and surgery.
Intercostal pain
Intercostal pain, also called intercostal neuralgia, is neuropathic pain along an intercostal nerve between the ribs, usually band-like or dermatomal, caused mainly by thoracotomy or herpes zoster and diagnosed after excluding cardiac, pulmonary, and gastrointestinal causes.
Intermediate age-related macular degeneration
Intermediate age-related macular degeneration (iAMD), AREDS category 3, is AMD with extensive medium drusen (63–124 μm) or large drusen (≥125 μm); it carries high progression risk to wet AMD or geographic atrophy and is treated with AREDS2 supplements.
Intermediate uveitis
Intermediate uveitis, also known as pars planitis, is an eye inflammation centered in the vitreous, marked by floaters, blurred vision, and snowbank or snowball formations.
Intermittent angle-closure
Intermittent angle-closure is a clinical form of primary angle-closure disease causing repeated, self-resolving episodes of blurred vision, haloes, and mild pain, which can progress to glaucoma if unrecognized.
Intermittent strabismus
Intermittent strabismus (ICD-11 9C80.3), chiefly intermittent exotropia, is an episodic eye misalignment controlled by fusion, appearing with fatigue, illness, or distance viewing; treated by observation, patching, over-minus lenses, or surgery.
Internal ophthalmoplegia
Internal ophthalmoplegia (ICD-11 9D01.0) is paralysis of the iris sphincter and ciliary muscle causing mydriasis and lost accommodation from parasympathetic disruption; distinct from internuclear ophthalmoplegia, a brainstem gaze disorder.
Internuclear ophthalmoplegia
Internuclear ophthalmoplegia (INO, MLF syndrome) is impaired adduction of one eye on horizontal gaze with abducting nystagmus and preserved convergence, caused by a medial longitudinal fasciculus lesion, usually multiple sclerosis in the young or brainstem stroke in older adults.