MAPT and Alzheimer disease: AD is the most common type of dementia (4), characterized by brain atrophy, synaptic dysfunction, histologic findings of neuritic plaques containing Aβ accumulation and neurofibrillary tangles containing phosphorylated tau, assessed through functional magnetic resonance imaging (MRI), cerebrospinal fluid measurements, positron emission tomography (PET) (5), and more recently with the introduction of a novel blood test (6).