ATXN8OS and Hyperreflexia: Two examples with different repeat expansions are SCA8, with a (CTG)n expansion in the ATXN8OS gene, and SCA10, containing an (ATTCT)n pentanucleotide repeat expansions in the ATXN10 gene.24, 25 An autosomal dominant disease caused by a CAG expansion in a UTR is SCA12, which is caused by an expansion of a CAG repeat in the 5′ UTR of the PPP2R2B gene.26 Among other things, the disease is characterized by the action tremor of various body parts and, in later stages, by hyperreflexia, gait ataxia as well as other signs of cerebellar dysfunction and dementia.