CSF2 and capillary leak syndrome: The pathophysiology of CLS in BMT-related CLS has not been fully studied, but some hypotheses on the contributing factors have been suggested such as pivotal contribution by circulating leukocytes, decreased C1 esterase inhibitor activity, elevated C4d concentrations, the use of G-CSF or GM-CSF, and elevation of terminal complement complex (TCC) levels [70,71,72,73].