In contrast with the strong familiality shown for disease duration after onset (Table 1), SOD1-mediated ALS showed modest familiality with respect to onset, accounting for only 42% of the variability in A4V and D90A fALS patients [98], and with only G37R and L38V mutations of SOD1 being significant covariates of age of onset [67]. The gene discussed is SOD1; the disease is amyotrophic lateral sclerosis.