[An apparently sporadic case with spinocerebellar ataxia type 1 (SCA1)].

We reported a sporadic case with late onset SCA1. There was no family history of neurological diseases. His parents had been healthy until they died at the age of 77 and 89 years, respectively. The patient noticed gait disturbance at age of 60. Thereafter, he gradually developed cerebellar ataxia, hyporeflexia, mild atrophy of the facial and limb muscles and moderate deep sensory disturbance. MRI of the brain showed moderate atrophy of the cerebellum and brainstem. Sequencing analysis of SCA1 gene demonstrated that the patient had an expanded allele with 40 CAG repeats and no CAT interruption. Consequently, he was diagnosed as having SCA1. These results suggest the possibility that among apparently sporadic cases with cerebellar ataxia, there are some cases of SCA1 with mild CAG repeat expansion.