Clinical characteristics of combined cases of spinocerebellar ataxia types 6 and 31.

This study reports the first family in which spinocerebellar ataxia type 6 (SCA6) and spinocerebellar ataxia type 31 (SCA31) mutations were seen. An index patient first presented to our hospital due to gait and speech disturbances. Subsequent clinical investigation of this patient and her family members revealed consistent pure cerebellar ataxia transmitted in an autosomal-dominant manner. Genetic examination unexpectedly demonstrated that two of the five affected individuals had expansions of SCA6 and SCA31, while two others had SCA31 alone and the remaining had SCA6. Clinical manifestations were more severe in individuals with combined mutations relative to those with single mutation, suggesting that the SCA6 and SCA31 mutations have a cumulative pathogenic effect.