AUTOSOMAL-DOMINANT CEREBELLAR-ATAXIA WITH RETINAL DEGENERATION (ADCA TYPE-II) IS GENETICALLY DIFFERENT FROM ADCA TYPE-I

Autosomal-dominant cerebellar ataxia (ADCA) type II is a neurodegenera tive disorder presenting with cerebellar ataxia and retinal degenerati on. We analyzed the clinical features of 21 patients with ADCA type II from 3 Moroccan and 2 French families. Mean age at onset was 17 years earlier in offspring than in their parents, compatible with anticipat ion. There was a suggestion of imprinting, with predominantly paternal transmission of early onset and severe forms of the affection. Candid ate genes were tested in the family with the largest pedigree. The two known loci for ADCA type I (spinal cerebellar ataxia 1 and 2) were ex cluded, as were candidate loci, retinitis pigmentosa L locus (RP1) and the genes for rhodopsine and peripherin-rds, responsible for autosoma l dominant retinitis pigmentosa. ADCA type II does not therefore resul t from an allelic mutation of the tested genes for ADCA type I or auto somal dominant retinitis pigmentosa.