C9orf72 and amyotrophic lateral sclerosis: The prevalence of pathological G4C2 expansions in the total European cohort (73/845, 8.64%) as well as in the FTLD-only (50/781, 6.40%) and FTLD–ALS (23/64, 35.94%) subgroups, was comparable to frequencies others and we published in the three original gene identification reports on C9orf72 [Dejesus-Hernandez et al., 2011; Gijselinck et al., 2012; Renton et al., 2011].