Apart from the well-known repeat expansion in the first C9orf72 intron, intermediate-length polyglutamine expansions in ATXN1 and ATXN2 has been associated with an increased risk for ALS [16,112,113,114], which acts as a disease modifier in C9orf72 expansion carriers [115], or modifier of ALS survival [116]. Here, C9orf72 is linked to amyotrophic lateral sclerosis.