ICD10 Code = G11.2
Genomic coordinate (human 13:70,107,421 ATXN8OS).
Cytoband (human 13q21.33 ATXN8OS).
OMIM’ genes @ 13q21.33 = 30 genes.
ClinVar = 19 ATXN8OS variants reported.
PANTHER Classification of ATXN8-Opposite Strand LncRNA is Unclassified.
Cytoband Structure: WCWCCWG6BGBGB2GB2
⠺ ⠉ ⠺ ⠉ ⠉ ⠺ ⠛⠼⠋ ⠃ ⠛ ⠃ ⠛ ⠃⠼⠃ ⠛ ⠃⠼⠃
Here I 🎁 present: “Spinocerebellar Ataxia Type-8“, VictorMcKusick, Mendelian Inheritance in Man’, 1966. (SCA8)
Spinocerebellar ataxia-8 (SCA8) is a neurodegenerative disorder caused by a CTG/CAG trinucleotide repeat expansion on the 13q21.33 cytoband.
Spinocerebellar ataxia type-8 is a slowly progressive inherited genetic disorder that causes degeneration of the cerebellum and leads to balance, coordination, and movement difficulties.
Overview & Genetics
Cause: Caused by a trinucleotide repeat expansion (CTG and CAG) on cytoband 13q21.33 in Ataxin genes of the ATXN8OS and ATXN8
- Inheritance: Autosomal dominant with reduced penetrance (not all individuals who inherit the mutation will develop symptoms).
- Repeat Size: Fewer than 50 repeats are typically normal; 80 to 1,300+ repeats increase disease risk.
Common Symptoms
- Initial signs: Balance and gait instability, scanning dysarthria (slow, drawn-out speech), and uncoordinated limb movements.
- Progression: Eye movement abnormalities (such as nystagmus or slow saccades), muscle spasticity, reduced vibration sense, and later-stage swallowing difficulties (dysphagia).
- Cognitive/other features: Some individuals experience mild cognitive impairment or executive dysfunction.
- Age of onset: Typically ranges from the third to fifth decade of life (30s to 50s), though onset can span from infancy to over age 60. Lifespan is generally not shortened.
Diagnosis & Management
- Diagnosis: Confirmed via a clinical neurological examination, neuroimaging showing cerebellar atrophy, and DNA-based genetic testing.
- Treatment: Supportive and symptomatic, relying on physical therapy, speech therapy, and mobility aids (such as canes or walkers) to maintain quality of life.
