Following linkage, mutations causing familial ALS have been identified in the genes SOD1[2]–[4], TARDBP[5], [6], and FUS(TLS)[7] accounting for about 20 to 30% of cases, and ALS2[8]–[10], SETX[11]–[13], and VAPB[14] accounting for some atypical, rare forms. The gene discussed is SETX; the disease is amyotrophic lateral sclerosis.