Among them, studies have reported that two of these mutants, P301L (also the most common mutation observed in the familial form [Poorkaj et al., 2001]), and R406W, were found to co‐deposit with native tau in the brain of patients affected with FTD (Miyasaka et al., 2001a, 2001b). The gene discussed is MAPT; the disease is frontotemporal dementia.