MAPT and early-onset autosomal dominant Alzheimer disease: Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by two main pathologic hallmarks: 1) extracellular senile plaques primarily comprised of accumulated amyloid β (Aβ) peptide and 2) intracellular neurofibrillary tangles comprised mainly of aggregated hyperphosphorylated tau [1], [2].