PDGFRB and Alzheimer disease: PDGFRB level was significantly reduced in the precuneus in AD compared toage-matched controls (P = 0.0002) (Figure 1(a)), and fibrinogen level, whichrises with BBB breakdown3,4,6 was significantly elevated (P = 0.0026)(Figure 1(b)).Fibrinogen level tended to vary inversely with PDGFRB level (r = −0.25,P = 0.054) (Figure 1(c)), suggesting that BBBbreakdown was related to lower pericyte content within the precuneus.