Tau pathology occurs in cognitively unimpaired individuals, as exemplified by Primary Age-Related Tauopathy (PART; Crary et al., 2014; Chung et al., 2021), and is also present in other neurodegenerative diseases, including progressive supranuclear palsy and corticobasal degeneration, raising questions about its specificity for AD. This evidence concerns the gene MAPT and Alzheimer disease.