ALS2 and amyotrophic lateral sclerosis: Mutations in SOD1 (the first gene historically identified as an ALS causing gene) [27], ALS2 (ALSIN; connected to juvenile-onset ALS [101], which is ALS starting before 25 years of age) [102], and senataxin (SETX; also seen in the juvenile form of ALS) are also associated with FALS [23].