The neuropathological hallmarks of Alzheimer’s disease (AD) are extracellular accumulation of aggregated amyloid-β (Aβ) peptides (plaques), often associated with degenerating neurites (neuritic plaques), and neurofibrillary degeneration characterized by intraneuronal aggregates of abnormally phosphorylated microtubule-associated tau protein (Ptau) in paired helical filaments (PHF), historically termed neurofibrillary tangles (NFTs). The gene discussed is MAPT; the disease is Alzheimer disease.