Distribution of five common subtypes of spinocerebellar ataxia in the Korean population

ABSTRACT

PURPOSE: Spinocerebellar ataxia (SCA) is a genetically heterogeneous disease for which more than 30 subtypes have been identified. However, 5 subtypes, SCA1, SCA2, SCA3, SCA6, and SCA7, account for more than 60% of cases. In this study, we report the distribution of these 5 subtypes in Korean patients. MATERIALS AND METHODS: Six hundred and thirty-eight unrelated patients with a presumptive diagnosis of SCA were included in this study. Trinucleotide (CAG) repeat number (TNR) repeat number was determined using fluorescently labeled primers and fragment analysis. RESULTS: A total of 128 unrelated patients (20.1% of all individuals tested) tested positive for SCA subtypes, including SCA1 (5 patients, 3.9% of those testing positive), SCA2 (38 patients, 29.7%), SCA3 (30 patients, 23.4%), SCA6 (39 patients, 30.5%), and SCA7 (16 patients, 12.5%). The mean copy number of pathogenic TNR alleles was 45+/-8.5 for SCA1, 42+/-3.1 for SCA2, 72+/-5.4 for SCA3, 23+/-1.5 for SCA6, and 50+/-11.4 for SCA7. TNR copy number was inversely correlated with onset age in SCA2, SCA6, and SCA7. CONCLUSION: SCA2, SCA3, and SCA6 are common SCA subtypes in Korean patients and could be screened as a first-line test. Expanded pathogenic allele size was associated with early onset age.