PAI-1 and TAFI in inflammatory bowel disease: the yin and yang of the fibrinolytic system.

In both Crohn's disease and ulcerative colitis, the two major forms of inflammatory bowel disease (IBD), an increased risk of thrombotic events has been demonstrated. Pathogenesis of thrombosis is multifactorial as various primary coagulation system abnormalities other than acquired factors have been reported. The fibrinolytic system has been widely investigated in IBD. Most of the available data report an imbalance in fibrinolytic capacity with a tendency toward a hypofibrinolytic state. Plasma thrombin-activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 are fundamental inhibitors of the fibrinolytic process and are also considered to be acute-phase reactants. Recent studies have shown an imbalance of plasminogen activator inhibitor-1 and thrombin-activatable fibrinolysis inhibitor, suggesting that these molecules might contribute to thromboembolic events in both forms of IBD.