MAPT and frontotemporal dementia: The level of biochemical diversity and, consequently, complexity of tau pathology is perhaps best illustrated by the simple fact that specific MAPT mutations are associated with specific forms of FTD; in contrast, the very same mutation (such as TAU P301L) can apparently lead to either CBD or FTDP-17 in the same family, suggesting that other factors (genetic, epigenetic, environmental) may influence which neurons are affected and when this occurs.