MAPT and frontotemporal dementia: In autosomal-dominant neurodegenerative disease, anatomical changes in brain structure occur years before symptom onset.1–4 In frontotemporal degeneration (FTD), the most common autosomal mutations are chromosome 9 open reading frame 72 (C9orf72), progranulin (GRN), and microtubule-associated protein tau (MAPT).