Spinocerebellar ataxia

Spinocerebellar ataxias are inherited neurodegenerative disorders that progressively impair movement coordination, often through degeneration of the cerebellum and connected pathways.

Cerebellum: A brain structure that helps coordinate movement, balance, and motor learning. Degeneration of this structure produces many of the characteristic coordination problems.
CAG repeat expansion: An increase in repeated CAG DNA sequences that can alter gene function or produce proteins with expanded polyglutamine tracts. Several spinocerebellar ataxias result from expanded CAG repeats in specific genes.
Spinocerebellar ataxia type 1: An autosomal dominant ataxia caused by a CAG repeat expansion in the ATXN1 gene. Its expanding repeat and progressive course typify one major subtype.
Genetic testing: Analysis of DNA to identify genetic variants associated with a condition or trait. Testing can identify the causative subtype when clinical features alone cannot.
Friedreich ataxia: An inherited ataxia usually caused by GAA repeat expansion in both copies of the FXN gene. Its usual recessive inheritance distinguishes it from many dominant spinocerebellar ataxias.
Ataxia: Impaired coordination of voluntary movement, often affecting gait, speech, or eye movements. It names the central motor impairment shared across these disorders.
Polyglutamine diseases: Inherited disorders caused by proteins containing abnormally long chains of glutamine residues. A subset of these ataxias belongs to this shared molecular disease group.
Spinocerebellar ataxia type 2: An autosomal dominant ataxia caused by a CAG repeat expansion in the ATXN2 gene. Slow eye movements can help distinguish this subtype from others.
Genetic counseling: Communication that helps people understand inherited conditions, genetic risks, and testing choices. Inheritance patterns make family risk and testing decisions central to care.
Multiple system atrophy: A progressive neurodegenerative disorder involving autonomic failure and parkinsonism or cerebellar ataxia. Its cerebellar form can resemble inherited ataxia but is typically sporadic.

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