[A familial case of spinocerebellar ataxia type 8 (SCA 8)--its clinical findings and an issue about the genetic basis].

We report a 28-year-old woman with spinocerebellar ataxia type 8 (SCA 8). This patient began to exhibit dysarthria at the age of 19. At the age of 25, she fell and hit her head while drunk and then a neurosurgeon found that her cerebellum was atrophic on cranial CT and MRI. Neurological examination on admission to our hospital revealed ataxic speech, limb ataxia and mild hyperreflexia without Babinski's sign. Cranial MRI showed only mild atrophy of the cerebellar hemispheres and vermis. Based on the results of genetic analysis, which showed expanded CTG repeats[(CTA) 13 (CTG) 5 (CCG) 4 (CTG) 124] on the SCA 8 locus at 13q21, she was diagnosed as having SCA 8. As clinical signs of SCA 8, Koob et al. reported limb spasticity and diminished vibration perception including cerebellar ataxia. Furthermore, Hirose et al. and Satoh et al. reported cases showing involuntary movements such as myoclonus or chorea including cerebellar ataxia. Our case and Ikeda's cases presented a pure cerebellar phenotype. We think that SCA 8 exhibits clinical heterogeneity. On the other hand, Stevanin et al. and Worth et al. expressed doubt as to whether the SCA 8 locus at 13q21 is the gene actually responsible for autosomal dominant cerebellar ataxia (ADCA). We conclude that it is necessary to accumulate additional case reports, and to further investigate the relationship between the clinical findings and the results of genetic analysis in order to determine whether or not the SCA 8 locus at 13q21 is the genetic basis for ADCA.