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Spinocerebellar ataxia type 2 (SCA2) is a subtype of type I autosomal dominant cerebellar ataxia (ADCA type I; see this term) characterized by truncal ataxia, dysarthria, slowed saccades and less commonly ophthalmoparesis and chorea. Prevalence is estimated to be 1-2 in 100,000 with significant geographical and ethnic variations. SCA2 presents in the 3rd or 4th decade (average age = 30 years; age range = 2-65 years). There is no distinct clinical feature that reliably distinguishes SCA2 from SCA1 although tremor and autonomic dysfunction are more common in SCA2. Parkinsonism is also a less common but well-documented manifestation. Disease course is similar in both SCA1 and SCA2 (see this term). The disease is caused by mutations in the ataxin 2 gene ATXN2 (12q23-q24.1). The normal CAG repeat length is 15-24; repeats 35 and longer are associated with the clinical manifestations of SCA2. Prognosis is relatively good in most cases. Cases with disease duration of longer than 20 years have been described. However, in some cases, especially those with younger age of symptomatic disease onset (under 20 years), progression may be rapid. |