Despite the genetic heterogeneity reported in familial amyotrophic lateral sclerosis (ALS) (fALS), Cu/Zn superoxide-dismutase (SOD1) gene mutations are the second most common cause of the disease, accounting for around 20% of all families (ALS1) and isolated sporadic cases (sALS). This evidence concerns the gene SOD1 and familial amyotrophic lateral sclerosis.