MAPT and early-onset autosomal dominant Alzheimer disease: Abnormal hyperphosphorylation and aggregation of Tau is usually considered as one of the important hallmarks shared by neurodegenerative Tauopathies including frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP‐17), progressive supranuclear palsy, corticobasal degeneration, Pick's disease and Alzheimer's disease (AD).2