MAPT and early-onset autosomal dominant Alzheimer disease: The pathological hallmarks of Alzheimer’s disease (AD) include the presence of extracellular amyloid plaques composed of aggregated forms of the Aβ peptide and intracellular neurofibrillary tangles composed of hyperphosphorylated, misfolded, and aggregated forms of microtubule-associated protein tau within the cytoplasm of certain neurons.