C9orf72 and frontotemporal dementia: FTD is commonly associated with a strong family history of neurodegenerative disease, and about one fourth of FTD can be attributed to an autosomal dominant familial form of FTLD, typically hexanucleotide expansion of chromosome 9 open reading frame 72 (C9orf72), progranulin gene (GRN) haploinsufficiency, and pathogenic variants of microtubule‐associated protein tau (MAPT).6, 7, 8