GRN and frontotemporal dementia: Genetic variants of FTD are very strongly associated with a particular protein pathology, with FTD due to mutations in the microtubule-associated protein tau (MAPT) gene, showing (as expected) tau pathology, whereas FTD due to mutations in the progranulin (GRN) gene and in chromosome 9 open reading frame 72 (C9orf72) shows TDP-43 pathology (of the types A and A or B, respectively) [4, 5].