GRN and frontotemporal dementia: Consequently, other than individuals with familial FTD caused by gene mutations giving rise to TDP-43 (C9orf72, GRN or TARDBP) or tau (MAPT) pathology, it is difficult to definitively determine, during life, the underlying neuropathology of most FTD syndromes, and presently impossible to do so for individuals with sporadic bvFTD.