Epidemiological and genetic studies of Huntington's disease in the San-in area of Japan

After the DNA diagnosis, we evaluated the prevalence of Huntington's disease (HD) in the San-in area of Japan, and confirmed the founder effect. There were 10 patients with HD in the San-in area, who were diagnosed clinically. The expansion of the CAG repeat was observed in 9 patients with HD members in their families, although those family members of the patients had already died. In the patient who had no positive family history, expansion of the CAG repeat was not seen. The prevalence of HD was 065/100,000 in this area. The common haplotype studied by the polymorphism marker of D4S136 was shown in all 9 HD patients, although they were observed in only 2.7% of the normal population. These results suggested a common ancestor of these HD patients.