Angioedema

What is angioedema?

Angioedema is swelling of the skin and underlying tissue.  It is most noticeable around the eyes, lips, hands, and feet, though it may affect other areas such as the throat or genitalia.  It may occur by itself, or it can be a component of an anaphylactic event.

What causes angioedema?

There are two main biological pathways that lead to angioedema.

• One pathway is mediated by histamine. Specific cells that reside in the skin, called mast cells, produce and secrete histamine, which in turn leads to inflammation of surrounding tissue, creating hives and swelling.  Common causes of histamine-mediated angioedema include foods, drugs, infections, and insect bites; however, in many cases the cause cannot be established.
• The second major cause of angioedema is much less common than histamine-mediated angioedema. This pathway involves the release of bradykinin, a molecule that acts on blood vessels and causes fluid leakage into the surrounding tissues.  The causes of bradykinin-mediated angioedema are usually due to a genetic defect (hereditary angioedema) or a medication side effect (such as ACE inhibitors).  In hereditary angioedema (HAE), a molecule named C1 inhibitor is either deficient or dysfunctional.

Treatment

Treatment for angioedema depends on whether it is histamine-mediated or bradykinin-mediated. 

• Histamine-mediated angioedema may be alleviated with withdrawal of the food or drug that caused it. If the cause is not found and it becomes a chronic problem (lasting more than 6 weeks), medical therapy may be initiated to relieve symptoms.  Medications include corticosteroids and antihistamines, though there are several other medications that may be used in particularly difficult cases, such as immunosuppressants.
• For bradykinin-mediated angioedema, if the cause is from a drug, then discontinuation of that drug will resolve the problem. If one has hereditary angioedema, treatment includes medical therapies aimed at replacing C1 inhibitor or reducing bradykinin levels.

Evaluation

To determine the cause of angioedema, complete history from the patient must be obtained.  Questions may include presence of prior episodes, duration of each episode, any suspected triggers, family history, and medication history.  Laboratory testing may be warranted to further clarify the type of angioedema.