Established biomarkers for the clinical in vivo diagnosis of prion disease are cerebrospinal fluid (CSF) 14-3-3 protein; total (t)-tau; t-tau/phosphorylated (p)-tau (or p-tau/t-tau) ratio; and, more recently, the prion real-time quaking-induced conversion (RT-QuIC) assay [8, 12–14]. Here, MAPT is linked to prion disease.