C9ORF72 is currently the only short tandem repeat (STR) expansion proven to cause ALS and frontotemporal spectrum disorder (FTD), however, different expanded STRs distinctive of other neurodegenerative disease like ATXN1 (spinal cerebellar ataxia type 1 (SCA1)), ATXN2 (SCA2), ATXN8 (SCA8) and HTT (Huntington’s disease) [15] have been found in clinically diagnosed ALS patients and FTD cases [16, 17]. This evidence concerns the gene C9orf72 and frontotemporal dementia.