A JAPANESE FAMILY WITH SPINOCEREBELLAR ATAXIA TYPE-6 WHICH INCLUDES 3INDIVIDUALS HOMOZYGOUS FOR AN EXPANDED CAG REPEAT IN THE SCA6 CACNL1A4 GENE/

We describe a Japanese family which includes 13 patients in five gener ations who have dominantly inherited ataxia. Molecular testing reveale d that in these patients the SCA6/CACNL1A4 gene carries the smallest k nown expanded CAG repeat (21 repeat units). The clinical features of t hese patients exhibited predominantly cerebellar ataxia with onset lat e in adult life and a very slowly progressive disease course. In addit ion, this SCA6 family showed some characteristic clinical and genetic features, including (1) apparent lack of genetic anticipation, with an intergenerationally stable CAG repeat size and (2) down-beat nystagmu s and diabetes mellitus in some of the SCA6 patients. We identified th ree individuals homozygous for an expanded CAG repeat (21/21) in the S CA6/CACNL1A4 gene, two of whom were symptomatic. There were no apparen t differences in clinical phenotype between the individuals homozygous and those heterozygous for an expanded CAG repeat in the SCA6/CACNL1A 4 gene. (C) 1998 Elsevier Science B.V. All rights reserved.