MAPT and Alzheimer disease: In addition, about 50% of PDD patients’ post-mortem brains showed Alzheimer’s disease (AD) like pathology, with extracellular β-amyloid plaques in cortical and subcortical regions, as well as intracellular hyperphosphorylated tau (p-tau) deposition in the hippocampal and neocortical regions in two-thirds of cases9,10.