MAPT and Alzheimer disease: Correlations of plasma tau or, more specifically, phosphorylated tau, have been found in patients with AD (Mielke et al., 2018; Thijssen et al., 2020), but the results of attempts to differentiate atypical parkinsonism syndromes (CBS and PSP) from healthy controls are still conflicting (Lin et al., 2018; Thijssen et al., 2020).