Hereditary Angioedema

As an allergist/immunologist, I am frequently asked to see patients with angioedema or swelling. Although many times the source of angioedema is due to exposure to a protein (antigen) to which that person is allergic, in some cases this is not true. One such instance is with Hereditary Angioedema or HAE.

HAE presents with episodes of swelling, usually of the extremities, face, trunk, genitals or swelling of the abdomen which can produce severe abdominal pain, nausea and vomiting. In some cases, patients with HAE have been taken to the operating room as the symptoms of an acute HAE attack can be similar to those seen with appendicitis. Unfortunately, these patients undergo removal of what later is found to be a normal appendix.

The most frightening complication of HAE is swelling of the airway which can lead to death. Unlike angioedema due to exposure to allergens, patients with HAE do not develop hives.

The cause of HAE is due to a lack of a specific protein or the presence of the protein, which does not work, called C1 esterase inhibitor (C1INH). C1INH is important to control inflammation. Therefore if one does not have the C1INH or has the C1INH which does not work, he or she will develop episodes of uncontrolled swelling. Unfortunately the development of swelling episodes is difficult to predict, although it can start after someone develops an infection, after dental surgery or after having an accident.

HAE is a pretty rare disease. About one in 10,000 to 50,000 patients has it. Although the name states that it is hereditary, 25 percent of the time it may not be hereditary (there is no family history of anyone with HAE) and it may be due to a sudden change in the gene for the C1INH protein.

How do we treat HAE? Treatment can be broken down into trying to prevent attacks and treatment of attacks when they happen. Unfortunately, the angioedema secondary to HAE cannot be treated with medications typically used for angioedema seen with allergic reactions, such as corticosteroids, epinephrine and anti-antihistamines (such as Claritin, Allegra, Zyrtec, Benadryl, etc).

Treatment of an attack. If the patient is having airway swelling, it is necessary for the patient to come to the nearest emergency room as he or she may need to have a tube placed in the airway to prevent it from closing. It may also be necessary for a patient to come in for HAE attacks to the emergency room if the attacks are extremely painful and the patient needs strong pain medications.

Unfortunately, there are really no good medications in the United States that have been approved for the treatment of HAE attacks. However, the good news is that there are a few companies studying medications, such as giving patients a functional C1INH protein. This medication has been shown in Europe to work well to treat an attack and even prevent attacks.

To prevent HAE attacks, there are a few methods.