Nervous and sensory conditions

Coccidioides meningitis

Coccidioides meningitis (coccidioidal meningitis), meningeal infection by Coccidioides immitis or posadasii; nearly always fatal untreated, treated with lifelong fluconazole 400-1200 mg daily, hydrocephalus in up to 40%.

Cochleovestibular malformation

Cochleovestibular malformation (ORPHA:502305), a rare congenital inner ear deformity causing severe to profound sensorineural hearing loss without cochlear nerve anomalies, classified by cochlea, modiolus, and lamina cribrosa morphology.

Cockayne syndrome

Cockayne syndrome (CS), also called dwarfism-retinal atrophy-deafness syndrome, is a rare autosomal recessive DNA repair disorder from ERCC6 or ERCC8 mutations, causing growth failure, microcephaly, photosensitivity, and neurodegeneration, with types I to III and COFS, and no cancer predisposition.

Cogan syndrome

Cogan syndrome, a rare autoimmune vasculitis of the inner ear and eye in young adults, causing interstitial keratitis and progressive deafness; typical versus atypical forms, diagnosis of exclusion, steroid treatment.

Cold-induced sweating syndrome

Cold-induced sweating syndrome (CISS, Crisponi syndrome) is a rare autosomal recessive CNTFR-related disorder caused by CRLF1 (~90%) or CLCF1 variants, featuring neonatal hyperthermia and feeding difficulties, then cold-triggered sweating and kyphoscoliosis.

Cold-stimulus headache

Cold-stimulus headache, also known as brain freeze, ice-cream headache, or Slurpee burn, is a common, short-lasting headache triggered by eating or breathing in something cold.

Coloboma of choroid and retina

Coloboma of choroid and retina (chorioretinal coloboma, ORPHA:98942) is a rare genetic birth defect with partial absence of retinal pigment epithelium and choroid, usually inferonasal, causing reduced vision and retinal detachment risk.

Coloboma of optic disc

Coloboma of optic disc (optic disc coloboma, ORPHA 98947) is a rare genetic, inferiorly decentered bowl-shaped excavation of the optic disc from failed embryonic fissure closure, causing reduced vision and retinal detachment risk.

Color blindness

Color blindness (color vision deficiency) is a reduced ability to distinguish colors, usually inherited X-linked recessively via OPN1LW/OPN1MW opsin gene mutations; red-green defects affect about 1 in 12 men, with no cure but tinted-lens aids and gene therapy trials for severe forms.

Combined hamartoma of the retina and retinal pigment epithelium

Combined hamartoma of the retina and retinal pigment epithelium (CHR-RPE) is a rare benign childhood retinal tumor of glial, vascular, and pigment epithelial tissue, often peripapillary, sometimes linked to neurofibromatosis, and mimicking melanoma or retinoblastoma.

Combined hyperactive dysfunction syndrome of the cranial nerves

Combined hyperactive dysfunction syndrome of the cranial nerves (ORPHA:221078, ICD-10 G52.7, ICD-11 8A85) is a rare acquired neuropathy combining trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia from neurovascular compression, in about 3% of HDS patients.

Combined oxidative phosphorylation defect type 21

COXPD21 (OMIM 615918) is an ultra-rare autosomal recessive mitochondrial encephalomyopathy caused by TARS2 variants, with complexes I, III, IV, V deficiency sparing II, neonatal onset, hypotonia, epilepsy, and hyperlactatemia.

Commotio retinae

Commotio retinae, or Berlin's edema, is transient gray-white outer retinal opacification after blunt closed-globe or blast trauma, seen in about 30% of hospital-treated eye injuries; photoreceptor outer segments are disrupted, and most cases resolve without treatment.

Communicating hydrocephalus

Communicating hydrocephalus (non-obstructive hydrocephalus, ICD-11 8D64.0): impaired CSF reabsorption without ventricular outflow blockage; causes include subarachnoid hemorrhage and meningitis; chronic form is normal pressure hydrocephalus, treated with shunts.

Complex febrile seizures

A complex febrile seizure is a fever-related seizure in a young child that is focal, lasts 15 minutes or more, recurs within 24 hours, or causes lasting weakness.

Compressive optic neuropathy

Compressive optic neuropathy is optic nerve dysfunction caused by sustained mechanical pressure, usually from tumors such as pituitary adenoma or meningioma, causing painless progressive vision loss.

Cone dystrophy with supernormal rod response

Cone dystrophy with supernormal rod response (CDSRR, KCNV2 retinopathy, OMIM 610356) is a rare autosomal recessive retinopathy from KCNV2 mutations, causing childhood photophobia, color vision loss, and a pathognomonic ERG with supernormal rod b-waves.

Confusional arousal

Confusional arousal, also called sleep drunkenness or Elpenor syndrome, is an NREM sleep parasomnia in which a person partially wakes confused and unresponsive, stays in bed, and later amnesic; one of three disorders of arousal with sleepwalking and sleep terrors.

Congenital achiasma

Congenital achiasma, also known as achiasmia, is a rare inherited disorder present from birth in which optic nerve fibers fail to cross, causing low vision, strabismus, and nystagmus.

Congenital ataxia

Congenital ataxia (ICD-11 8A03.0) is a group of early-onset, usually nonprogressive cerebellar ataxias with hypotonia, developmental delay, and cognitive impairment, classified into cerebellar malformation, syndromic, hypoplasia, and pontocerebellar hypoplasia forms.

Congenital cataract microcornea with corneal opacity

Congenital cataract microcornea with corneal opacity (CCMCO) is a rare inherited eye disorder in which cataract, small corneas, and corneal clouding cause blindness from birth.

Congenital cataracts-facial dysmorphism-neuropathy syndrome

CCFDN, congenital cataracts-facial dysmorphism-neuropathy syndrome, is a rare autosomal recessive CTDP1 disorder seen almost exclusively in Roma people, causing congenital cataracts, facial dysmorphism, hypomyelinating neuropathy, and rhabdomyolysis risk.

Congenital conductive hearing loss

Congenital conductive hearing loss (ICD-11 AB50.0) is hearing loss present at birth from external or middle ear malformations such as canal atresia or ossicular anomalies, occurring in about 1 per 11,000-15,000 patients, managed with amplification or surgery.

Congenital corneal opacity

Congenital corneal opacity (CCO) is clouding of the cornea present at birth or within the first 4 weeks of life, also called congenital corneal opacification. Peters anomaly is its most common cause; key genes include PAX6, FOXC1, FOXE3, and B3GALTL.

Congenital dacryocele

Congenital dacryocele, also called congenital dacryocystocele, is a distended lacrimal sac in newborns from double nasolacrimal obstruction (Hasner and Rosenmüller valves), presenting as a bluish medial canthal mass, sometimes with intranasal cysts, dacryocystitis, or respiratory distress.

Congenital ectropion uveae

Congenital ectropion uveae (congenital iris ectropion syndrome) is a rare unilateral eye defect with iris pigment epithelium on the anterior iris, angle dysgenesis, and glaucoma in 80-90% of cases, often linked to NF-1.

Congenital eyelid retraction

Congenital eyelid retraction, classified as ICD-11 LA14.05, is a rare kinetic eyelid anomaly present at birth where one eyelid sits too high or too low.

Congenital fibrosis of extraocular muscles

Congenital fibrosis of extraocular muscles (CFEOM), a congenital cranial dysinnervation disorder, causes non-progressive restrictive ophthalmoplegia with ptosis; five subtypes map to genes including KIF21A, PHOX2A, and TUBB3.

Congenital forms of nystagmus

Congenital forms of nystagmus, now called infantile nystagmus syndrome (INS), are involuntary eye oscillations beginning in the first 6 months of life, affecting 1 in 1000-1500 children, linked to albinism, retinal dystrophies, and FRMD7 mutations.