ATXN1 and amyotrophic lateral sclerosis: Traditional genetic testing for the ALS patient did not identify mutations in the ALS-causing genes SOD1, C9ORF72, FUS, TARDPB, and ANG. The phenotypic variability of this family is further complicated by the presence of a “central branch” in the genealogical tree (termed as MN-branch), including SCA1 patients showing early signs and symptoms of lower MN involvement, reinforcing a putative pathogenic link between SCA1 and other degenerative MN diseases, including ALS (Figure 1).