Elevated plasmin-alpha 2-antiplasmin complex levels in hereditary angioedema: evidence for the in vivo efficiency of the intrinsic fibrinolytic system.

The contact activation and fibrinolytic systems were assessed in 5 patients with hereditary angioedema (HAE). Reductions in F XII levels and increase in kallikrein-like activity in some patients indicated activation of the contact (intrinsic) system of coagulation. A great increase in plasmin-alpha 2-antiplasmin complex in all subjects indicated that in this disease, there is a constantly ongoing fibrinolysis. Since C1-inhibitor, the deficient protein in HAE, is a poor inhibitor of the well-known extrinsic (tissue-type) plasminogen activator, but the major inhibitor of the contact activation system and a related in vitro phenomenon termed intrinsic fibrinolysis, our data show that this fibrinolytic system is also sometimes operating efficiently in vivo. Furthermore, the known clinical data on HAE are compatible with a role of intrinsic fibrinolysis in the pathophysiology of this disease.