Autosomal dominant cerebellar ataxia (ACDA) type III is a group of neurodegenerative disorders characterized by mostly pure cerebellar syndromes with occasional non-cerebellar signs (e.g. pyramidal signs, peripheral neuropathy, writer's cramp) and includes spinocerebellar ataxia (SCA) type 5 (SCA5), SCA6, SCA11, SCA26, SCA30, and SCA31.