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What causes hereditary angioedema (HAE) attacks?

While scientists don't know everything about the events that lead to an attack, studies show that most people with hereditary angioedema (HAE) either do not have enough protein in their blood, or it doesn't work the way it should.


C1-INH deficiency, or C1-INH, does not work properly


Increased activity of protein called plasma


Excess bradykinin is produced


Swells of an HAE attack occur

Normally, C1 esterase inhibitor (C1-INH) helps to regulate plasma kallikrein. When there is not enough functioning C1 esterase inhibitor (C1-INH), the activity of plasma kallikrein increases. Too much plasma kallikrein activity triggers the release of bradykinin. Increased bradykinin levels cause blood vessels to release fluid and result in the localized swelling and pain of an HAE attack.

I can't be sure what causes my HAE attacks, but one thing I do know is the impact they have on my life. So I'm going to do all I can to manage them.

Kevin, Living with HAE

Kevin, Living with HAE.

Is there a genetic test for hereditary angioedema (HAE)?

To know for certain that you have HAE, a blood test is recommended. Your doctor will measure your levels of the proteins C4 and C1 esterase inhibitor. If you have HAE, this test can also help determine whether you have Type I or Type II HAE. In some instances, you may need to take a genetic test.

Because HAE is rare, few people know about it, including many doctors. If you think there is a chance you have HAE, check out the HAE Disease Education Brochure. Then talk to your doctor about it so he or she can decide if you should be tested for HAE.

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