MAPT and neurodegenerative disease: Genetic frontotemporal dementias (gFTDs) represent a group of progressive neurodegenerative diseases characterised by a progressive decline of executive, behavioural and language functions, frequently resulting from mutations in the genes chromosome open reading frame 72 (C9orf72), progranulin (GRN) or microtubule-associated protein tau (MAPT).1 Neurofilament light chain (NfL)—an intermediate filament that constitutes part of the neuronal cytoskeleton—is released after neuronal damage into the interstitial fluid, cerebrospinal fluid and blood.