Alzheimer's disease (AD) is a devastating neurodegenerative syndrome characterized by drastic and progressive dementia and changes in behavior, allied to accumulation in the brain of extracellular senile plaques composed mainly of amyloid β protein (Aβ), intraneuronal neurofibrillary tangles containing hyperphosphorylated tau protein, and chronic neuroinflammation. The gene discussed is MAPT; the disease is Alzheimer disease.