MAPT and tauopathy: For example, phosphorylated tau (pTau) species in plasma and CSF have been reported in a variety of tauopathies (Giagkou et al., 2024; Rojas et al., 2018; Schoonenboom et al., 2012; Thijssen et al., 2021), making this a difficult biomarker to rely on for a disease-specific diagnosis.