The histopathological hallmarks of AD are extracellular amyloid plaques composed predominantly of the amyloid-β (Aβ) peptide, and neurofibrillary tangles consisting of abnormally aggregated, hyperphosphorylated tau protein within neurons (Castellani et al, 2010; Holtzman et al, 2011; Serrano-Pozo et al, 2011). The gene discussed is MAPT; the disease is Alzheimer disease.