C9orf72 and amyotrophic lateral sclerosis: Approximately 10% of all ALS patients suffer from familial ALS that is associated with a number of genetic variants, including superoxide dismutase 1 (SOD1), fused in sarcoma (FUS), TAR DNA binding protein 43 (TDP-43), and chromosome 9 open reading frame 72 (C9orf72).