MAPT and Alzheimer disease: By contrast, tau pathology in Pick’s disease (PiD) (3R), Alzheimer’s disease (AD) (3R/4R), and primary age-related tauopathy (PART) (3R/4R) is largely limited to neurons, although rare astrocytic pathology with variable mixtures of 3R and 4R tau has been reported in Pick’s disease [2, 9, 10, 19, 20] (Fig. 1).