Spinocerebellar ataxia type 4 and 16q22.1-linked Japanese ataxia are not allelic

Sirs: Spinocerebellar ataxia type 4 (SCA4) was first described in a large family of Scandinavian origin from Utah and is linked to chromosome 16q22.1 [1]. The clinical phenotype is characterized by progressive cerebellar ataxia in combination with sensory axonal neuropathy. A second family was reported from Germany, the SCA4 candidate region could be refined to a 3.69 cM interval (7.94 Mb) [2–4]. Meanwhile, the gene locus responsible for a pure cerebellar ataxia in six Japanese families was mapped to the same region [5–7].