Adult Onset Inherited Spinocerebellar Ataxias

This group of spinocerebellar ataxias (SCA) comprises autosomal dominant diseases, the majority are caused by triplet (CAG) repeat expansions. To date, 17 genetic types (SCA 1 through 17) have been identified with their chromosomal loci. The genes of SCA-1, -2, -3, -7, -8, -10, and -11 encode for the protein ataxin. Mutations of the SCA-6 gene affect calcium-channel function (Table 5.17). The prevalence of SCAs is estimated at 5 per 100,000 persons. The age of onset is between 40 and 50 years. It is earlier in successive generations (anticipation); occasional infantile and childhood cases occur, depending on the repeat length.

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