MAPT and early-onset autosomal dominant Alzheimer disease: Aggregation of the tau protein is a neuropathological hallmark of several neurodegenerative disorders classified as tauopathies, including frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), corticobasal degeneration (CBD), progressive supranuclear palsy (PSP), Pick’s disease (PiD), and Alzheimer’s disease (AD).