However, there have been fewer studies examining changes in the familial forms of FTD due to pathogenic variants in the progranulin (GRN) and microtubule-associated protein tau (MAPT) genes and a pathogenic expansion in chromosome 9 open reading frame 72 (C9orf72), which account for about one-third of all FTDs.4-9. Here, MAPT is linked to frontotemporal dementia.