OBJECTIVE

To review the mechanisms by which bradykinin is generated in hereditary angioedema (HAE) (C1 inhibitor deficiency), including the role of human plasma proteins and endothelial cells.

DATA SOURCES

Published articles in reviewed journals that address (1) the fundamentals of bradykinin formation, (2) interactions between kinin-forming proteins and endothelial cells, (3) clinical evidence that bradykinin causes swelling in HAE, and (4) therapeutic options focused on inhibition of the plasma kallikrein-kinin cascade.

STUDY SELECTION

Historical articles that have made fundamental observations. Recent articles that address evolving concepts of disease pathogenesis and treatment.

RESULTS

C1 inhibitor deficiency causes dysregulation of the plasma bradykinin-forming cascade with overproduction of bradykinin due to uninhibited effects of activated factor XII and plasma kallikrein. Swelling in HAE and production of bradykinin are localized (and may then disseminate); activation along the endothelial cell surface involves cell membrane ligands of factor XII and high-molecular-weight kininogen, release of endothelial cell heat shock protein 90, activation of the high-molecular-weight kininogen-prekallikrein complex, and endothelial cell activation at the B2 receptor. Attacks of swelling may be terminated by treatment with a kallikrein inhibitor or B2 receptor blockade. Replenishing C1 inhibitor can abort attacks of swelling and provide prophylaxis with intravenous administration.

CONCLUSIONS

Bradykinin is the mediator of swelling in types I and II HAE and is overproduced because of a deficiency in C1 inhibitor. Inhibition of bradykinin formation by novel agentscan provide targeted therapeutic approaches that address the pathophysiologic abnormalities.