However, male sex emerges from both studies as a crucial interacting factor in the biology of C9orf72-mediated disease, in contrast to previous analyses performed in non-expanded ALS cohorts, that reported that female sex was an independent predictor of faster functional decline (Chiò et al., 2012; Watanabe et al., 2015). This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.