MAPT and Alzheimer disease: Neuropathological features in the two major neurodegenerative diseases, Alzheimer's disease (AD) and Lewy body disease (LBD) are characterized by aggregation of abnormal proteins, including both amyloid-β (senile plaques) and phosphorylated tau (neurofibrillary tangles) in AD, and α-synuclein (Lewy bodies) in LBD.