Autosomal dominant pure cerebellar ataxia: A clinical and genetic analysis of eight Japanese families

We carried out linkage analysis and clinical assessment on 41 patients with autosomal dominant pure cerebellar ataxia (ADCA) type III from eight Japanese families. The presenting symptom was gait ataxia in all patients, with the average age of onset at 46.0 +/- 9.0 (SD) years. The mean age of onset was 3.2 +/- 7.7 years earlier in offsprings than in their parents, suggesting mild, but not dramatic, anticipation. Other neurological features were restricted to cerebellar symptoms in spite of a long duration of illness of up to 41 years. The disease progression was uniformly slow, and earlier onset did not show different or severe clinical phenotype. Linkage analysis using four microsatellite markers (D11S905, D11S903, GATA2A01 and D11S913) excluded the first gene locus for ADCA type III [spinocerebellar ataxia (SCA) type 5]. The present study provides new genetic evidence, in addition to that suggested by clinical difference, that ADCA type III represents a group of heterogeneous conditions.