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

Objectives - We report the results of clinical and genetic studies from 2 related Japanese kindreds with spinocerebellar ataxia type 2 (SCA2). Material and methods - Family A showed 19 patients through 4 generations, while family B showed 6 patients, including dizygotic twin brothers, through 3 generations. We performed clinical, radiological, neurophysiological, and genetic analyses in the family members. Results - Neurologic analysis of 13 affected patients revealed a mean age at onset of 43.5 years. The most common neurologic 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 showed 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 clinically heterogeneous than previously thought. PCR is useful in differentiating SCA2 from other types of inherited ataxia.