More than 30 genes have been linked to ALS and mutations in chromosome 9 open reading frame 72 (C9orf72), superoxide dismutase1 (SOD1), transactive response DNA-binding protein 43 (TDP-43), or fused in sarcoma (FUS) are responsible for most of the familial ALS cases. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.