Figure 2. Relationship of repeat length to disease features in spinocerebellar ataxia type 3 (SCA3).
Normal CAG repeat length in SCA3 is 12 to ~44, with disease repeats ranging from ~60–87. Clinical subtypes 1 (dystonia), 2 (ataxia), and 3 (weakness) tend to be associated with the range of indicated repeat lengths. Rare intermediate repeat lengths may be associated with restless legs syndrome.