An intronic GGGGCC (G4C2) hexanucleotide repeat expansion (HRE) in the first intron of the C9orf72 gene is the most common mutation causing ALS (C9‐ALS), accounting for up to 40% of familial and 10% of sporadic cases [6, 7, 8, 9]. This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.