What You Need to Know About Hereditary Angioedema

Learn what can trigger an episode, when symptoms can be life threatening and other facts about this rare condition.

What You Need to Know About Hereditary Angioedema

Hereditary angioedema, abbreviated as HAE, is a disorder where people experience recurring episodes of severe swelling. This swelling can occur throughout the body, affecting areas such as the hands and feet, the face, the genitals, the gastrointestinal tract and the throat. HAE is a rare condition, affecting between 6,000 and 10,000 people in the United States. For most people, symptoms first appear in childhood and get worse with the onset of puberty.

Here are seven things you should know to better understand this condition.

HAE symptoms are unpredictable
The frequency, duration and severity of HAE episodes vary from person to person. Many people experience episodes several times a month, while others only experience episodes occasionally. The areas of the body affected by HAE episodes do not follow a pattern—for example, you may experience swelling in the hands during one episode, and swelling in the abdomen during a different episode. Swelling can also occur in multiple sites during the same episode. While symptoms can be difficult to predict, there are treatments available that can help prevent episodes from occurring.

HAE episodes may have triggers
A trigger is factor that acts as a catalyst for symptoms. While the majority of HAE episodes occur without any identifiable trigger, mental stress and anxiety, physical exertion, surgery, dental work, injuries, illnesses, and changes in the weather are all listed as possible triggers for HAE episodes. Women have a few additional triggers to be mindful of—menstruation, pregnancy and using oral contraceptives. Identifying triggers is an important step in managing HAE, because it can help you help you prevent and anticipate episodes.

HAE episodes can be life threatening
Swelling in the intestinal tract or the throat can be life threatening. In addition to causing abdominal pain, nausea, diarrhea and vomiting, swelling in the intestinal tract can lead to hypovolemic shock, a condition resulting from severe fluid loss that can cause organ failure and death. An episode of swelling in the throat is extremely dangerous—and about 50 percent of people with HAE will experience at least one episode of this in their lifetime. Swelling in the throat can close the airways, making it difficult or impossible to breathe and potentially causing death by asphyxiation. Any swelling in the throat should be considered a medical emergency.

Even when symptoms aren’t life threatening, they can be debilitating. Swelling in the hands and feet can make doing basic everyday tasks impossible when you’re experiencing an episode. Many patients with HAE report that it has a negative impact on education, career, relationships and quality of life.

HAE is caused by a genetic mutation
In the majority of cases, hereditary angioedema is the result of mutations in the SERPING1 gene. This gene is important to the production of a protein called C1 inhibitor, which suppresses other proteins that promote inflammation in the body. When a person has HAE, their body does not make the C1 inhibitor protein, or C1 inhibitor does not function properly. This leads to an excess amount of proteins that promote inflammation and fluid leaking from cells—which leads to episodes of swelling that are the major symptom of HAE.

There are three types of HAE
Hereditary angioedema can be classified as Type I, Type II or Type III. About 85 percent of people with HAE have Type I, where the body does not produce the C1 inhibitor protein. Roughly 15 percent have Type II, where the body produces C1 inhibitor, but the protein functions abnormally.

Type III is very rare, and there is still much researchers do not understand about Type III. People who have this type have C1 inhibitor that functions normally, and the angioedema has other causes. Another name for Type III is “HAE with Normal C1 Inhibitor.”

HAE is not always inherited
Children who have a parent with HAE have a 50 percent chance of inheriting HAE. Unlike many other inheritable disorders, there are no carriers for Type 1 or Type II HAE; those who do not have these conditions cannot pass it on. There is evidence that some people may carry the genetic mutation for Type III.

An estimated one in four people with HAE did not inherit the condition from a parent, but instead developed HAE due to a new mutation of the gene that occurred at conception. Those who develop HAE through this spontaneous genetic mutation can still pass it on to their children.

There are treatments available for HAE
There are numerous prescription medicines available that can help treat and manage HAE. Treatments involve boosting levels of C1 inhibitor to counteract inflammation. Some treatments are taken to prevent attacks, others are taken in anticipation of an attack, or to halt and reduce the severity of an attack. Speak with your healthcare provider about the treatment option that is best for you.

Medically reviewed in January 2018.

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