It has been previously reported that coagulation/fibrinolysis proteases (thrombin, coagulation factors IX, XI, X and plasmin) may act as natural C3 and C5 convertases [29], and coagulation factor IX is significantly higher in PCOS, suggesting that factor IX might play a role in the elevation of C5a in patients with PCOS. The gene discussed is C5; the disease is polycystic ovary syndrome.