AD is the most common form of senile dementia and is characterized by senile plaque (SP) formation, which are composed of extracellularly deposited β-amyloid (Aβ) and also neurofibrillary tangles (NFT) that contain the intracellular aggregated hyperphosphorylated microtubule-associated protein (MAP): tau. The gene discussed is MAPT; the disease is Alzheimer disease.