MAPT and Alzheimer disease: Approximately 25% of patients with NFV PPA have FTLD transactive response DNA binding protein 43-kDa (TDP-43) pathology, usually of type A [2], and 12–25% have Alzheimer disease (AD) pathology [3, 4] (for review see [6]), characterized by neurofibrillary tangles composed of balanced 3R/4R tau, and fibrillar amyloid plaques.