Nervous and sensory conditions

Rest tremor

Rest tremor: involuntary rhythmic shaking of a body part not voluntarily activated and supported against gravity; the classic 4-6 Hz pill-rolling tremor of Parkinson's disease, distinguished from action tremor.

Restless legs syndrome

Restless legs syndrome (Willis-Ekbom disease): neurological disorder causing an urge to move the legs at rest, worse at night. Linked to brain iron deficiency, dopamine dysfunction, BTBD9/MEIS1 genes; treated with iron, gabapentinoids, avoiding dopamine agonist augmentation.

Restrictive ophthalmopathy

Restrictive ophthalmopathy (拘束性眼症), ICD-11 9C82.3, is mechanical restriction of eye movement from stiff or fibrotic extraocular muscles, chiefly in thyroid eye disease (Graves' ophthalmopathy), causing diplopia and limited elevation.

Retinal atrophy

Retinal atrophy: wasting of the retinal pigment epithelium and neurosensory retinal cells from inherited, age-related, toxic, or secondary causes; includes geographic atrophy, ARCA, and gyrate atrophy, classified by OCT consensus terms cRORA and iRORA.

Retinal breaks without detachment

Retinal breaks without detachment (ICD-11 9B73.4): full-thickness retinal tears, holes, or dialyses without retinal separation. Symptomatic horseshoe tears need treatment; asymptomatic breaks are usually observed.

Retinal cavernous hemangioma

Retinal cavernous hemangioma (CHR, cavernous hemangioma of the retina) is a rare benign retinal vascular hamartoma with grape-like saccular clusters, usually unilateral and asymptomatic; intracranial hemangiomas occur in 14% of cases.

Retinal cysts

Retinal cysts (ICD-11 9B73.2; 網膜嚢胞) are closed sacs in the retina, congenital or acquired, including ora serrata and parasitic cysts; distinct from retinoschisis and microcystoid degeneration, imaged mainly by OCT.

Retinal detachment

Retinal detachment: separation of the retina from the retinal pigment epithelium, an ophthalmic emergency. Rhegmatogenous type is most common; Gonin's 1919 break theory and ignipuncture founded modern repair; over 90% single-surgery success today.

Retinal ischaemia

Retinal ischaemia is an insufficient blood supply to the retina, the light-sensitive tissue lining the back of the eye, and a driving factor in diabetic retinopathy and retinal vein occlusion.

Retinal macular dystrophy type 2

Retinal macular dystrophy type 2 (MCDR2, OMIM 608051), also called PROM1-related or autosomal dominant bull's-eye macular dystrophy, is a rare dominant macular dystrophy causing slowly progressive bull's eye maculopathy with mild vision loss.

Retinal migraine

Retinal migraine (ocular migraine), ICHD-3 code 1.2.4, is a rare migraine subtype with fully reversible monocular visual disturbance (scotomata, scintillations, blindness) followed within 60 minutes by headache; a diagnosis of exclusion, treated with verapamil, avoiding triptans and beta-blockers.

Retinal oedema

Retinal edema, also called retinal edema, is fluid buildup within the retina that causes blurring and distortion of central vision, most often from diabetic retinopathy, retinal vein occlusion, or wet age-related macular degeneration.

Retinal telangiectasis

Retinal telangiectasis is a rare anomaly of the retinal capillaries marked by dilated, tortuous vessels, aneurysms, and leakage, spanning entities from Coats disease to idiopathic macular telangiectasia.

Retinal vasculitis

Retinal vasculitis: inflammatory infiltration of retinal vessel walls, idiopathic or secondary to infections (tuberculosis, herpes), Behçet disease, sarcoidosis, or systemic vasculitis; diagnosed clinically with angiography, treated by cause.

Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations

RVCL-S (also CRV, HERNS, HVR) is a rare autosomal dominant small vessel disease caused by C-terminal TREX1 mutations, causing retinopathy, brain lesions, liver and kidney disease, onset ages 30-50, premature death, no cure, crizanlizumab trials.

Retinal venous occlusions

Retinal venous occlusions (RVO): blockages of retinal veins, central (CRVO) or branch (BRVO), causing sudden painless vision loss and macular edema; anti-VEGF injections are first-line treatment.

Retinoschisis

Retinoschisis: splitting of the neurosensory retina, either common acquired (senile, outer plexiform layer, ~7% over age 40) or X-linked juvenile (RS1 gene, males). Distinct from retinal detachment; OCT differentiates them.

Revesz syndrome

Revesz syndrome, also called dyskeratosis congenita with bilateral exudative retinopathy or Revesz-DeBuse syndrome, is an extremely rare autosomal dominant TINF2-related severe variant of dyskeratosis congenita marked by exudative retinopathy, intracranial calcifications, and early bone marrow failure.

Reye syndrome

Reye syndrome, also called Reye hepatocerebral syndrome, is a rare childhood illness with brain swelling and fatty liver that follows viral infections and has been linked to aspirin.

Richards-Rundle syndrome

Richards-Rundle syndrome, also called ketoaciduria-intellectual disability-ataxia-deafness syndrome, is an extremely rare autosomal recessive neurodegenerative disorder with ataxia, hearing loss, hypogonadism, and ketoaciduria, described in only one family.

Rieger anomaly

Rieger anomaly is a congenital eye defect featuring iris stroma thinning, hole formation, corectopia, and features of Axenfeld's anomaly, with glaucoma in about half of patients.

Ring chromosome 15 syndrome

Ring chromosome 15 syndrome (ring 15, r(15)) is a rare chromosomal disorder from deletion of 15q and ring formation, causing growth retardation, short stature, intellectual disability, dysmorphism, and skin pigment spots; prevalence under 1 in 1,000,000.

Ring chromosome 22 syndrome

Ring chromosome 22 syndrome (r(22), Ring 22) is a rare chromosomal disorder, prevalence under 1 in 1,000,000, in which chromosome 22 forms a ring with lost tips; it causes developmental delay, hypotonia, microcephaly, severe speech delay, and can cause Phelan-McDermid syndrome via SHANK3 loss.

Ring dermoid of cornea

Ring dermoid of cornea (ring dermoid syndrome, OMIM 180550, ORPHA:91481) is a rare autosomal dominant condition of bilateral annular limbal dermoids extending onto cornea and conjunctiva, linked to PITX2 mutations, with fewer than 30 reported cases and no extraocular anomalies.

RNU4-2-related autosomal dominant neurodevelopmental disorder

RNU4-2-related autosomal dominant neurodevelopmental disorder, also called ReNU syndrome, is a genetic disorder marked by developmental delay, poor or absent speech, intellectual disability, hypotonia, microcephaly, and seizures, identified in 2024.

Rosette-forming glioneuronal tumor

Rosette-forming glioneuronal tumor (RGNT) is a rare WHO grade 1 mixed neuronal-glial brain tumor of the fourth ventricle or cerebellum in young adults, defined by neurocytic rosettes, a pilocytic astrocytoma-like glial component, and FGFR1 hotspot mutations.

Roussy-Lévy syndrome

Roussy-Lévy syndrome (hereditary areflexic dystasia), described 1926, is an autosomal dominant CMT phenotype with gait ataxia, pes cavus, areflexia, and postural tremor, usually from the PMP22 17p11.2 duplication (CMT1A), sometimes MPZ mutation (CMT1B).

Rubella panencephalitis

Rubella panencephalitis (progressive rubella panencephalitis, PRP) is an extremely rare, fatal slow-virus encephalitis appearing years after congenital or childhood rubella, with dementia, ataxia, and seizures; fewer than 20 cases reported.

Rubeosis of iris

Rubeosis of iris (rubeosis iridis, iris neovascularization, NVI) is abnormal new blood vessel growth on the iris surface, secondary to retinal ischemia from diabetic retinopathy, central retinal vein occlusion, or carotid disease, and leading to neovascular glaucoma.