59 FTD patients with MAPT (n = 10), GRN (n = 25), or C9orf72 (n = 24) mutations, 149 presymptomatic mutation carriers (24 MAPT, 79 GRN, 46 C9orf72), 127 non-carrier relatives. The gene discussed is C9orf72; the disease is frontotemporal dementia.