Most ALS cases are sporadic amyotrophic lateral sclerosis(SALS) with only 5–10% genetically linked familial amyotrophic lateral sclerosis (FALS); 20% of FALS cases show missense mutations in the Cu/Zn superoxide dismutase (SOD1) gene (Rosen et al., 1993). Here, SOD1 is linked to familial amyotrophic lateral sclerosis.