ABSTRACT
This chapter summarizes work on Spinocerebellar Ataxia Type 6 (SCA6) reported by this laboratory and by others. The clinical features of the SCA6 patients in families described by us and those from other studies are very similar and consist predominantly of mild but slowly progressive cerebellar ataxia of the limbs and gait, dysarthria, nystagmus, and mild vibratory and proprioceptive sensory loss. In the Japanese population, SCA6 makes up a large proportion of the inherited form of cerebellar ataxia but in other populations its frequency is much lower. The transmission of the SCA6 allele is generally stable but three cases of small expansion have been observed in over 50 parent-child transmission. Two homozygotes for SCA6 alleles have been reported. In one SCA6 homozygote with 23 CAG repeats, the age-of-onset was not any earlier than SCA6 heterozygote patients with the same repeat length, but the progression of the ataxia was much more rapid.
