MAPT and early-onset autosomal dominant Alzheimer disease: Alzheimer's disease was first described by the psychiatrist and neuropathologist Alois Alzheimer in 1907 as a disease that manifested extracellular amyloid plaques and intracellular neurofibrillary tangles (NFTs) in the brain, composed of abnormally folded amyloid‐β42 (Aβ42) and tau proteins, as the most pathologically important phenotypic hallmarks.