Differences in biomarkers of inflammation and coagulation may help to distinguish PAH from CTEPH. Apart from our findings regarding fibrinogen concentrations, differences between PAH and CTEPH were found for IL-6, CRP, soluble CD-40-ligand and fractalkine82527. All these data confirm that both diseases, despite the significant overlap, may have distinct pathophysiology. CRP, for instance, was found to be elevated both in PAH and CTEPH82527, but was only correlated with outcome in PAH and not in CTEPH patients.