Some ALS-causing genes—such as superoxide dismutase 1 (SOD1) and fused in sarcoma/translocated in sarcoma (FUS/TLS)—have been identified in both sALS and fALS patients, whereas other culprit genes are either predominantly sALS-associated (e.g. unc-13 homolog A, UNC13A) or fALS-associated (e.g. D-amino acid oxidase, DAO). Here, SOD1 is linked to amyotrophic lateral sclerosis.