MAPT and Alzheimer disease: Alzheimer's disease is clinically characterised by a global deficit in cognition ranging from loss of memory to impaired judgement and reasoning.43 Neuropathological hallmarks of AD are extracellular β-amyloid (Aβ) plaques and intracellular neurofibrillary tangles composed of abnormally hyperphosphorylated microtubule-associated protein tau.