Discover what causes HAE
Although not all is known about the events that induce angioedema attacks in hereditary angioedema (HAE), studies show that most people with HAE either do not have enough of an important protein called C1 esterase inhibitor or it doesn't work the way it should.
When there isn't enough C1 esterase inhibitor or it isn't working properly, it initiates episodes of swelling.
A deficiency in working C1 esterase inhibitor causes the condition
C1 esterase inhibitor is a protein found in the blood. When it's at normal levels and working properly, it helps regulate plasma kallikrein activity by blocking its ability to split proteins apart, which is linked to leakage of fluid from the blood vessels and swelling of the surrounding tissues. Because people with HAE don't have enough working C1 esterase inhibitor, the body has an overactive kallikrein system with nothing to keep it in check. As a result, kallikrein is able to split a protein apart, which releases another protein called bradykinin.
Bradykinin overproduction causes the symptoms
Having too much bradykinin allows fluid that is normally contained within the blood vessels to leak into the surrounding tissues. This is thought to cause the swelling experienced during an HAE attack.