PGF and acute chest syndrome: The leukocytes adhesion to endothelium is a primary event in initiating vascular occlusion and secondarily causes RBCs to adhere to leukocytes or to endothelium.31 Brittain et al 201032 found significantly elevated PlGF in SCD compared with healthy controls but did not observe any association of PlGF with the frequency of acute pain episodes or history of acute chest syndrome.