Incidence of genetic subgroups of hereditary spinocerebellar ataxia in Fukushima Prefecture.

The prevalence of each type of hereditary spinocerebellar ataxias (SCAs) was genetically determined in Fukushima Prefecture, and the results were compared to those in other areas of Japan. The genetic analyses were done in 29 patients with dominant SCA and 5 patients with SCA with negative family history. Machado-Joseph disease was identified in 41.3% of the cases, SCA6 17.2%, dentatorubral-pallidoluysian atrophy (DRPLA) 6.9% and unknown 34.5%. The incidence is clearly different from those of Miyagi and Yamagata Prefectures as SCA1 has not been identified in our region, and is in fact similar to that of Hokuriku or Kanto Provinces. An apparent difference in the incidence of each SCA may be attributed to the historical and geographic regional difference in the distribution of inhabitants and also to the small size of the SCA population we have so far investigated. In addition, 2 of the 3 genetically identified DRPLA in this study were not clinically diagnosed, and one of them was thought to be sporadic. Late onset DRPLA may thus be misdiagnosed to other disease categories, when dementia was not apparent at the time of onset.