C9orf72 and amyotrophic lateral sclerosis: Of note, in ALS and ALS–FTD patients, additional mutations in ALS genes may be revealed in NEK1 carriers, as identified in two Belgian siblings with FALS and cognitive impairment in which NEK1 p.Ser1036* loss-of-function mutation was associated with C9orf72 repeat expansion and TUBA4A p.Thr381Met variant, presenting with early disease onsets [63,71].