MAPT and supranuclear palsy, progressive, 1: Tauopathies are distinguished by the relative abundance of 3R- and 4R-tau isoforms in their respective filaments: AD and CTE are mixed 3R/4R tau tauopathies; PSP and CBD are primarily 4R-tauopathies; and PiD is primarily a 3R-tauopathy8–10.