The key to what goes wrong in hereditary angioedema is in the name of the disorder. The term “angio” is derived from the Greek word for “vessel,” in this case referring to blood vessels, and the word “edema” means “swelling.” All mutations that cause HAE ultimately affect how your body controls inflammation, and all can lead to severe swelling. There’s no way to prevent or get rid of HAE if you carry one of the genetic mutations that causes it, but you may be able to control your symptoms by identifying possible triggers and taking prescribed medications. (1)
Hereditary Angioedema (HAE) Causes: A Handful of Genetic Mutations
Hereditary angioedema occurs as a result of a genetic mutation. The mechanism of an HAE attack varies depending on which HAE genetic mutation you have. There are two known mutations — in the SERPING1 gene and the F12 gene — but scientists suspect there are other as yet unidentified genes that cause HAE. The type of treatment you are prescribed will be influenced by which mutation you carry.
Mutations in the SERPING1 Gene Cause HAE Types 1 and 2
Changes in the C1NH gene, also known as the SERPING1 gene, cause type 1 and type 2 HAE. The SERPING1 gene tells the body how to make a protein called C1 inhibitor, which is important for controlling swelling. In type 1 HAE, your body does not make enough C1 inhibitor. With type 2, your body makes enough of the protein, but it doesn’t work properly. Without normal and functional amounts of C1 inhibitor, the body generates too much bradykinin — a protein peptide. Bradykinin causes excessive fluid to leak through the walls of body tissues, which leads to inflammation and episodes of swelling. (2,3,4)
Mutations in the F12 Gene Cause HAE Type 3
Type 3 HAE is an extremely rare form of the disease, and the exact prevalence isn’t known. Scientists believe some cases of type 3 HAE are caused by mutations in the F12 gene. In type 3 HAE, C1 inhibitor levels and function are normal, but the F12 mutation dysregulates the system by which the body makes a protein called coagulation factor XII, which plays a role in stimulating inflammation and producing bradykinin. Other cases of type 3 HAE have no known causes. Researchers believe unidentified genes play a role. (2,3,4) HAE can also develop in people with no family history when a spontaneous gene mutation happens during conception. (3,4)
Testing for Hereditary Angioedema (HAE)
If HAE runs in your family, you might want to consider getting tested for it. Or, you might decide that you want your family members to get tested if you have the disease. Even though this is a disease that is caused by a genetic mutation, genetic testing, which analyzes changes in genes, isn’t needed to confirm a diagnosis of HAE. The simplest form of testing involves a blood test that measures levels of C1-inhibitor or how well this protein works in your body, and sometimes other biomarkers of the disease, in your bloodstream. Genetic testing can be used as a follow-up test to confirm the results of the blood test, if necessary. Testing for HAE is a personal choice, and it can be scary for some people. But, knowing that you have the disease can help prepare you or your loved ones for future attacks, allowing you to take advantage of preventive treatments early and take control of your health. (5)
What Are the Early Signs of a Hereditary Angioedema (HAE) Attack?
Most HAE attacks occur when your body needs the C1 inhibitor but can’t make enough of the protein or use it properly. (4) Attacks may involve severe swelling in the skin, abdomen, or throat. While it’s hard to predict when an HAE episode will happen, some people report symptoms that forecast a problem. These signs can occur several hours or even a full day before the attack. Common signs of an HAE attack include: (4)
FatigueIrritabilityWeaknessNauseaPink rings or rash
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What Are Hereditary Angioedema (HAE) Attack Triggers?
Certain factors may prompt an HAE attack. These include: (4,6)
Stress Anxiety and stress can both be triggers.Common Illnesses Having an injury or an infection, such as the cold or flu, may bring on an HAE episode.Pregnancy, Menstruation, or Breast-Feeding Many women report an increase in the number of attacks during their period or other times when they experience hormonal changes.Drugs Medicines such as oral contraceptives and angiotensin-converting enzyme (ACE) inhibitors are linked to an increase in the number and severity of HAE episodes.Medical Procedures Some studies have shown that attacks after surgery are common. They typically happen 4 to 30 hours later. (4) Having a dental procedure may also trigger an HAE episode.
Some people also report swelling after engaging in activities such as: (6)
Typing or writingPushing a lawn mowerShovelingHammeringOther physical activities
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Avoiding Hereditary Angioedema (HAE) Triggers
It might be impossible to avoid all HAE triggers, but there are some steps you can take to lessen your chances of a severe attack. For instance, try to keep stress levels low. Also, talk to your doctor before taking any new medications or having a surgical procedure that could provoke a swelling episode. And, take all your prescribed preventive medicines. Some people keep a journal of their attacks. This can help you better identify triggers.
