Within familial ALS, 60% of familial cases are accounted for by 4 genes including GGGGCC hexanucleotide repeats in chromosome 9 open reading frame 72 (C9orf72; 40%) [27, 28], missense mutations in superoxide dismutase 1 (SOD1; 12%) [29], point mutations in TAR DNA binding protein 43 (TDP-43; 4%) [10] and point mutations in the fused in sarcoma gene (FUS; 4%) [30, 31]. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.