MAPT and prion disease: The PGRN/p-tau ratio (Fig. 2b) was significantly lower in AD than in FTLD-TDP and FTLD-tau (p = 0.0017 and 0.0007, respectively) and significantly higher in FTLD-tau than in prion disease and DLB (p = 0.0237 and p = 0.0170, respectively).