Alzheimer's disease is a progressive neurodegenerative disease that is characterized at the molecular level by the accumulation of two specific protein-based pathologies within the brain: amyloid plaques, composed of extracellular amyloid-β (Aβ) peptide, and intracellular neurofibrillary tangles (NFTs), composed of abnormally hyperphosphorylated tau protein. Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.