Alzheimer's disease (AD) is characterized by two neuropathological hallmarks, extracellular amyloid β (Aβ) deposits in the brain parenchyma (amyloid plaques) and cerebral blood vessels (cerebral amyloid angiopathy, CAA) and abnormal aggregates of hyperphosphorylated tau protein in brain neurons (neurofibrillary tangles, NFTs). Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.