MAPT and Alzheimer disease: Early Tau pathology (detected as AT8 immunoreactivity) in DS appears by middle age (30–40 years) (Head et al., 2003; Davidson et al., 2018), after Aβ pathology is established, and follows a distribution pattern resembling that of AD, starting in the entorhinal cortex and spreading to the hippocampus and the neocortex (Davidson et al., 2018).