C9ORF72, the most frequent genetic etiology, represents 25% of familial FTD cases (DeJesus-Hernandez et al., 2011; Renton et al., 2011), 80% of FTD-ALS familial cases and also explains 40% of pure familial ALS (without FTD) (Majounie et al., 2012). The gene discussed is C9orf72; the disease is frontotemporal dementia.