Excluding C9orf72 repeat expansions, 17.6% of clinically diagnosed ALS and FTD cases had at least one expanded short tandem repeat (STR) allele reported to be pathogenic or intermediate for another neurodegenerative diseases such as ATXN1 [spinal cerebellar ataxia type 1 (SCA1)], ATXN2 (SCA2), ATXN8 (SCA8), TBP (SCA17), HTT (Huntington’s disease), DMPK [myotonic dystrophy type 1 (DM1)], CNBP (DM2), and FMR1 (fragile-X disorders) [10]. This evidence concerns the gene ATXN1 and myotonic dystrophy type 1.