MAPT and Alzheimer disease: Alzheimer's disease (AD) is the most common type of dementia and is characterised pathologically by the intraneuronal accumulation of neurofibrillary tangles (NFT) containing tau and ubiquitin, and by the extracellular accumulation of amyloid-β (Aβ) in brain tissue and in artery walls as cerebral amyloid angiopathy (CAA).