C9orf72 and frontotemporal dementia: As previously reported, the C9orf72 mutation accounts for 23.5–47% of familial ALS/FTD and 4.1–21.0% of sporadic ALS in white populations (Dejesus-Hernandez et al., 2011; Renton et al., 2011; Gijselinck et al., 2012).