We first sought evidence for aberrant methylation in the affected twins at promoters of genes already implicated in ALS:ALS2, ADAR, ATXN2, C9orf72, FUS, OPTN, PFN1, SETX, SOD1, SPG11, TARDBP, VAPB, VCP and UBQLN2 [28]. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.