ATXN2 and amyotrophic lateral sclerosis: To our knowledge, the normal CAG repeat size in ATXN2 is 15–29 (34) and the different ranges of CAG repeat numbers contribute to different phenotypes (Figure 4), such as SCA2 (repeats >34), ALS (repeats: 29–34) and Parkinsonism (repeats: 34–49).