SCA42 mutation analysis in a case series of Japanese patients with spinocerebellar ataxia.

Spinocerebellar ataxia (SCA) is a group of dominantly inherited heterogeneous disorders in which 43 subtypes have been identified to date. Recently, Japanese and French families with SCA type 42 (SCA42) were found to have a missense mutation (c.5144G>A; R1715H) in CACNA1G. We performed genetic analysis of 84 unrelated families to find the prevalence of SCA42 in Japan. Two families were found to have the previously reported missense mutation. Clinical presentations of the affected members of these families were similar to those of the previously reported French and Japanese families. Our study demonstrates that SCA42 exists in small numbers in Japan, and further supports the idea that SCA42 is a slowly progressive, pure cerebellar ataxia.