Chinese patients with Huntington's disease initially presenting with spinocerebellar ataxia.

Recent studies have described Huntington's disease (HD) patients with atypical onset of ataxia. Symptoms in these patients can overlap with those of spinocerebellar ataxia (SCA). We retrospectively examined clinical data for 82 HD probands and found 7 had initially been clinically diagnosed as SCA cases. Clinical features in these patients were further investigated and the number of CAG repeats in the huntingtin (HTT) gene was determined by direct sequencing. Genetic screenings for SCAs in the 7 patients were all negative. By contrast, HTT was heterozygous in each patient. The distribution of CAG number in the 7 patients was statistically the same as that in the other 75 patients. Each of 7 HD patients had presented with atypical onset of ataxia. The mean time from onset to HTT genetic testing was 5.6 ± 5.52 years. Three of the patients developed chorea, but the others did not. Our observations confirm the clinical heterogeneity of HD in Han Chinese. Based on these findings, testing for HTT expansions should be considered for clinically diagnosed SCA patients who test negatively in genetic screening of SCA genes.