What is hereditary angioedema?

Hereditary angioedema (HAE) is a rare condition that occurs in a person’s immune system and causes swelling in the body, typically in the airways and parts of the body like the face, stomach, or hands. The swelling that happens because of HAE is different than other forms of allergic reactions, like hives, because HAE causes swelling underneath the skin. The cause of HAE is a low level of or irregular function of a specific protein called the C1-inhibitor that affects the blood vessels, causing swelling. HAE is often a genetic condition that is usually passed down in a family from one person to another.^Footnote1

HAE can be triggered by factors such as anxiety, stress, or trauma. Individuals with HAE type 1 have lower than normal levels of the C1-inhibitor protein. This lower level is caused due to a defective gene in the body. HAE type 1 is the most common form of HAE. Individuals with HAE type 2 have normal or higher than normal levels of the C1-inhibitor protein, but this protein does not work correctly in the body. Symptoms between HAE type 1 and 2 are the same.^Footnote2

There is no current cure for HAE. However, there are treatments for HAE that involve intravenous infusions (fluids being administered into a vein) or subcutaneous injections (a needle being inserted into an arm). These HAE treatments attempt to prevent HAE attacks but are not able to be taken on-demand whenever an attack is occurring.^Footnote3

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