ALS can be either sporadic (sALS) or familial (fALS), and four genes (superoxide dismutase 1 (SOD1), TAR DNA binding protein (TARDBP), fused in sarcoma (FUS), and C9ORF72) are causally linked to the pathogenesis, and account for the majority of fALS cases. This evidence concerns the gene SOD1 and amyotrophic lateral sclerosis.