The polymorphic hexanucleotide repeat expansion (HRE) in the C9ORF72 gene is the major genetic cause of amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) (DeJesus-Hernandez et al, 2011; Renton et al, 2011). This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.