In particular, the high frequency in Caucasian ALS patients, the wide phenotypic heterogeneity associated with its mutations, the availability of a quick and relatively simple diagnostic test, and the recent therapeutic advances in the field make SOD1, alongside C9ORF72, the first candidate gene to be sought in patients with an MND and require that its mutations should be ruled out before pursuing next-generation sequencing (NGS) approaches. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.