MAPT and Alzheimer disease: Some of these processes begin decades before the onset of clinical symptoms, which is why the most recent AT(N) scheme, published by the National Institute on Aging and Alzheimer’s Association, proposed establishing a definition of AD based on the assessment of disease biomarkers, namely Aβ plaque (A), fibrillary tau (T), and neurodegeneration or neuronal damage (N), and not on clinical symptoms [8].