Spinocerebellar ataxia type 6

Spinocerebellar ataxia type 6, often shortened to SCA6, is a rare, late-onset, autosomal dominant disorder. Like other spinocerebellar ataxias it is characterized by dysarthria, abnormal eye movements, peripheral neuropathy and ataxia of gait, stance and limbs that arise from cerebellar dysfunction. The dysfunction is permanent and progressive, which separates it from episodic ataxia type 2, although some families show a mix of both patterns. Unlike other types, SCA6 is not fatal. It is caused by mutations in CACNA1A, a gene encoding a calcium channel subunit, usually CAG trinucleotide repeat expansions that yield proteins with long stretches of glutamine and a tendency to clump inside cells. Symptoms typically begin between ages 43 and 52, and diagnosis is by genetic testing. Physical therapy and speech pathology help patients manage symptoms.