Clinical and genetic studies of spinocerebellar ataxia type 2 in Japanese kindreds

Objectives - We report the results of clinical and genetic studies from 2 r elated Japanese kindreds with spinocerebellar ataxia type 2 (SCA2). Materia l and methods - Family A showed 19 patients through 4 generations, while fa mily B showed 6 patients, including dizygotic twin brothers, through 3 gene rations. We performed clinical, radiological, neurophysiological, and genet ic analyses in the family members. Results - Neurologic analysis of 13 affe cted patients revealed a mean age at onset of 43.5 years. The most common n eurologic finding was cerebellar ataxia with deep sensory disturbance. Slow saccades was found only in the younger patients below age 35 years. Nerve conduction studies revealed subclinical sensory neuropathy. Brain MRI showe d the presence of pontocerebellar atrophy. Genetic study using PCR revealed that all affected patients had an expanded CAG allele in the ataxin-2 gene , which led to a final diagnosis of SCA2. Conclusion - SCA2 may be more cli nically heterogeneous than previously thought. PCR is useful in differentia ting SCA2 from other types of inherited ataxia.