Hereditary angioedema (HAE) is an inherited disease that causes repeated episodes of swelling.
Angioedema means swelling beneath the surface of the skin. In HAE, the swelling and associated inflammation most often occurs in the face, hands, feet, arms and legs. Dangerous swelling in the airways — trachea (windpipe) or larynx (voice box) — or intestinal tract can also occur
There is a wide range of severity for people with HAE. Some people with HAE have mild inflammation that requires no treatment. Others may need to be hospitalized for life-saving treatment.
There are three types of HAE: type 1, type 2, and type 3. Each type has its own causes and symptoms.
Each type of HAE has a different cause.
Type 1 is caused by mutations in the SERPING1 gene. This gene makes the protein C1 inhibitor. The C1 inhibitor is part of the body’s complement system. The complement system is made up of small proteins that assist the immune system. This system helps control inflammation. People with type 1 don’t make enough of the C1 inhibitor. Because of this, the body can’t control inflammation.
People with type 2 also have a mutation in the SERPING1 gene. They make enough C1, but the C1 doesn’t work properly.
There aren’t any abnormalities found with the C1 inhibitor in people with type 3. Type 3 has several potential causes. This condition occurs mainly in women and can be made worse with pregnancy or use of birth control medications.
It’s also associated with a mutation in the factor XII (F12) gene. This gene makes coagulation F12. F12 assists in the blood clotting process. It can also stimulate inflammation. In people with type 3, too much coagulation F12 is produced.
HAE mutations are dominant. This means you only need to inherit one copy of a mutated gene to develop HAE. A parent with HAE has a 50 percent chance of passing it on to their child.
In rare cases, a person will develop HAE when neither parent is affected. This means that a spontaneous gene mutation has occurred. This accounts for about 20 percent of HAE cases. Although technically the person’s HAE isn’t inherited, they will be able to pass it on to their children.
Symptoms are grouped by the area of inflammation. Swelling may affect the abdomen, face, throat, limbs, and intestines. An episode of swelling may last for up to four days
Symptoms of intestinal swelling include:
- severe abdominal pain and cramping
- nausea and vomiting
- shock (in severe cases)
Symptoms of throat inflammation include:
- hoarse voice
- difficulty swallowing
- difficulty breathing
Other symptoms include swelling in the:
These symptoms may also be caused by other conditions. Always seek medical attention if you have unexplained swelling.
Call 911 immediately if you develop throat swelling or difficulty breathing or talking. These are potentially life-threatening symptoms. They could lead to shock or death.
Blood tests can check the C1 inhibitor level and function. Because the Cl inhibitor is part of the complement system, blood tests for complement components C4 and C2 may also help diagnose HAE.
There’s no cure for HAE. Treatment focuses on relieving symptoms and preventing flare-ups.
Several types of medication and therapies can be used to treat HAE.
Epinephrine is usually used in life-threatening situations to keep the airway open. The medication tightens blood vessels and relaxes muscles in the throat. Epinephrine is more effective than antihistamines. Antihistamines haven’t been proven to be as effective in treatment of HAE. Epinephrine also works more quickly, making it a better option in emergency situations.
Other treatments can include:
- fresh frozen plasma
- attenuated androgens
If you have severe throat swelling, you may need respiratory treatments. These are given in a hospital setting.
Several types of medication have been approved to prevent flare-ups. These drugs are available by prescription only. Some must be administered in a controlled healthcare setting.
- C1-inhibitors (Cinryze, Berinert)
- ecallantide (Kalbitor)
- icatibant (Firazyr)
HAE can be life threatening. Swelling in the throat can cause difficulty breathing, and eventually death. Prompt treatment with intubation or tracheotomy can be life-saving. Hypovolemic shock due to loss of blood from blood vessels must be treated promptly with fluid replacement.
If you have trouble breathing, seek immediate medical attention.
If you have HAE, speak with your doctor about how to manage your flare-ups. Together, you can develop the best course of treatment for your specific type of HAE.