The fibrinolysis system is responsible for removing blood clots. Hyperfibrinolysis describes a situation with markedly enhanced fibrinolytic activity, resulting in increased, sometimes catastrophic bleeding. Hyperfibrinolysis can be caused by acquired or congenital reasons. Among the congenital conditions for hyperfibrinolysis, deficiency of alpha-2-antiplasmin (alpha-2-plasmin inhibitor) or plasminogen activator inhibitor type 1 (PAI-1) are very rare. The affected individuals show ahemophilia-like bleeding phenotype. Acquired hyperfibrinolysis is found in liver disease, in patients with severe trauma, during major surgical procedures, and other conditions. A special situation with temporarily enhanced fibrinolysis is thrombolytic therapy with drugs which activate plasminogen, e.g. for use in acute ischemicevents or in patients with stroke. In patients with severe trauma, hyperfibrinolysis is associated with poor outcome.
Bleeding is caused by the generation of fibrinogen degradation products which interfere with regular fibrin polymerization and inhibit platelet aggregation. Moreover, plasmin which is formed in excess in hyperfibrinolysis can proteolytically activate or inactivate many plasmatic or cellular proteins involved in hemostasis. Especially the degradation of fibrinogen, an essential protein for platelet aggregation and clot stability, may be a major cause for clinical bleeding.