PHENOTYPE VARIATION CORRELATES WITH CAG REPEAT LENGTH IN SCA2 - A STUDY OF 28 JAPANESE PATIENTS

Spinocerebellar ataxia-2 (SCA2) is an autosomal dominant ataxia caused by an abnormal CAG repeat expansion in a novel gene on chromosome 12q 24.1. The size of the mutant allele is unstable during transmission, a nd correlates inversely with age at onset. We studied eight Japanese S CA2 families,:including 28 patients, to assess the effect of repeat le ngth on the phenotype features of SCA2. Frequencies of slow eye moveme nts (SEM), reflex activity, dementia, choreiform movements, and axial tremor correlated significantly with CAG repeat size. Parkinsonism was seen in a man homozygote for SCA2 mutation. The clinical variety of S CA2 is apparently influenced by the size of the mutant allele, as is t he case in other CAG repeat disorders. (C) 1998 Elsevier Science B.V. All rights reserved.