An extended phenotype of an early-onset inherited nonprogressive cerebellar ataxia syndrome.

A father and son with presumed dominantly inherited, nonprogressive, early-onset cerebellar ataxia are reported. The clinical features are similar to those in other reports of this rare disorder, but magnetic resonance imaging revealed generalized atrophy of the cerebellum and not localized vermal atrophy as previously noted. This family illustrates either an extended phenotype of the previously reported disorder or possibly an unique type of autosomal dominant cerebellar ataxia.