The neuropathology of AD is characterised by widescaleatrophy, regional neuronal loss, gliosis and two pathognomonic entities; extracellular plaques, made up primarily of peptides called beta-amyloid (Aβ) and neurofibrillary tangles (NFT) made up chiefly of filaments of hyperphosphorylated microtubule-associated protein tau (tau). The gene discussed is MAPT; the disease is Alzheimer disease.