Since the turn of the century, the ability to diagnose AD pathology in living people has been made possible by the development of radioligands for Aβ positron emission tomographic (PET) scans (Klunk et al., 2004; Schilling et al., 2016) and tau PET scans (Marquie et al., 2015; Leuzy et al., 2019), magnetic resonance imaging (MRI) for neurodegeneration (Frisoni et al., 2010) and analysis of cerebrospinal fluid (CSF) for Aβ and tau species (Blennow, 2004; Holtzman, 2011). Here, MAPT is linked to Alzheimer disease.