Mutations in the SETX gene that encodes the protein senataxin are associated with two rare autosomal diseases of distinct inheritance: spinocerebellar ataxia, autosomal-recessive, with axonal neuropathy 2 (SCAN2, formerly known as AOA2, OMIM #606002), and amyotrophic lateral sclerosis 4 (ALS4, OMIM #602433), a juvenile form of ALS (Table 1). Here, SETX is linked to amyotrophic lateral sclerosis.