ATXN3 and Parkinson disease: Our findings may suggest that, although a pathological number of CAG repeats in SCA3 was the major determinant of neurological dysfunction in these four patients, the addition of borderline repeats in SCA2 or other repeat expansion genes may play a role in the heterogeneity of phenotypes such as parkinsonism features, suggesting an underlying complex interaction among repeat expansion genes (de Castilhos et al., 2014; Tezenas du Montcel et al., 2014).