AD is a multifactorial neurodegenerative disease that involves a combination of the extracellular accumulation of beta-amyloid (Aβ) plaques, intracellular neurofibrillary tangles (NFTs), composed of hyperphosphorylated tau protein, chronic neuroinflammation, and reactive gliosis, ultimately leading to neuronal loss and declining cognition. The gene discussed is MAPT; the disease is Alzheimer disease.