Powered By
Continue with Facebook
Continue with Email
You might assume that hereditary angioedema (HAE) is always passed down through families.
However, although many people inherit an HAE-related gene change from a parent, some are the first in their family to have the condition. That means you can have HAE even if no one else in your family has been diagnosed.
If you have HAE without a family history, you’re in a smaller group of people with the condition. Even so, HAE still begins with a change in your genes. Read on to learn more about HAE that isn’t inherited.
Sign up to view the results!
Continue with Facebook
Continue with Email
About 75 percent of people with HAE inherited it from a parent who has it too. HAE is inherited most of the time through something called an autosomal dominant inheritance pattern.
An autosomal dominant pattern of inheritance means that only one of your parents needs to have HAE in order for you to have a chance of developing it too. If you have a parent with HAE but don’t inherit the condition, you won’t be able to pass it down to your children.
Most cases of inherited HAE arise from a genetic variant (or genetic mutation) of the SERPING1 gene. This gene helps your body make C1 inhibitor (C1INH), a protein that helps control inflammation and swelling. A SERPING1 variant can cause low C1INH levels or keep the protein from working properly, leading to a buildup of bradykinin that triggers swelling.
A less common form is called HAE with normal C1 inhibitor (HAE-nC1INH). Some cases of HAE-nC1INH are linked to a variant in the F12 gene, which helps make a protein involved in blood clotting and inflammation. Certain F12 variants can increase bradykinin activity and lead to swelling.
If one parent has HAE, their children have a 50 percent chance of inheriting HAE from the parent. They also have a 50 percent chance of not inheriting HAE.
The other 25 percent of HAE cases aren’t inherited from a parent. If you’re in this category, you probably don’t know of any family members with HAE.
HAE that isn’t inherited from a parent occurs because of a type of gene variant called a de novo gene variant. Here, gene changes happen spontaneously, often in sperm or egg cells before fertilization. They can also occur in an embryo (a fertilized egg) during early pregnancy.
De novo gene variants leading to HAE usually occur in the SERPING1 gene. This means that most people with HAE without a family history experience swelling because of a C1INH deficiency.
In some cases, HAE in people who don’t have an immediate family member with HAE can be misdiagnosed as another condition that causes similar swelling. HAE without a family history may be misinterpreted as either allergic angioedema or idiopathic angioedema.
Allergic angioedema describes swelling that occurs during an allergic reaction, usually within two hours of exposure to something you’re allergic to. Common allergens that might cause allergic angioedema include latex, foods like milk or shellfish, and insect venom.
Allergic angioedema often causes hives along with the swelling, which are itchy welts or bumps on the skin. Hives aren’t associated with HAE, so their presence can make it easier to distinguish the two.
Idiopathic angioedema is swelling without a clear cause, which can also come with hives. Idiopathic angioedema may or may not respond to antihistamines, which are medications used to treat allergic angioedema since the chemical histamine drives the swelling.
In 30 percent to 50 percent of cases, idiopathic angioedema appears to be linked to autoimmune disorders such as systemic lupus erythematosus (SLE), the most common form of lupus.
Some swelling can come from an acquired C1INH deficiency that doesn’t occur because of a de novo or inherited gene change. You might develop an acquired C1INH deficiency after a major illness like cancer or a severe infection.
Having an accurate diagnosis is important because it allows you to treat your HAE effectively, reduce swelling episodes, and avoid potentially life-threatening swelling in the airway.
Not all types of angioedema respond to the same treatments. For example, treatments that work well for allergic angioedema won’t make a difference for swelling from HAE.
Swelling from HAE with a C1INH deficiency won’t improve if you take antihistamines even though antihistamines can very effectively treat other types of angioedema.
Treatments for HAE with a C1INH deficiency often involve C1INH replacement therapy to replace low levels of C1INH. Some treatments reduce the risk of swelling episodes while others can treat HAE swelling as it’s happening.
If you visit your doctor about swelling episodes or other common HAE symptoms, your doctor will ask you to describe the symptoms and when they occur. Your symptoms might happen in response to triggers like stress or trauma, or they might happen with no clear cause at all.
Your doctor will also ask about your family history before recommending any further angioedema tests. Even if you’re uncertain of family members’ exact diagnoses, it can be helpful to mention any known history of swelling in your family.
Based on your answers about your swelling and family history, your doctor may recommend tests for specific types of HAE. Additionally, allergy testing can help your doctor rule out allergic angioedema as a cause of the swelling.
Blood tests can help your doctor see if you have a C1INH deficiency. They might find that you don’t have enough C1INH in your blood, or any at all. Some people have plenty of C1INH, but it doesn’t function as it should to prevent excessive swelling.
Blood tests can evaluate C1INH levels and function, so their results can point to HAE as a diagnosis.
If your doctor thinks you might have HAE based on the results of blood tests and a physical exam, they might recommend genetic testing to see if you have gene changes linked to HAE. Some genetic tests can detect the de novo gene changes that cause HAE without a family history.
It might also be helpful for your family members to get a blood test for a C1INH deficiency or undergo genetic testing for HAE. Since HAE is a rare disease, you might have a family member who has it but has been misdiagnosed with another form of angioedema.
Tell your doctor if you experience swelling episodes but don’t know why. They might refer you to an HAE specialist who knows how to recognize and manage HAE.
While most cases of HAE come from a parent with HAE, you might be in the smaller group of people with HAE without a family history. Your doctor can help ensure you get the right diagnosis and can treat your angioedema accordingly.
On myHAEteam, people share their experiences with hereditary angioedema, get advice, and find support from others who understand.
Are you the only one in your family with HAE? Let others know in the comments below.
Get updates directly to your inbox.
Continue with Facebook
Continue with Email
Continue with Facebook
Continue with Email
Become a member to get even more
Join
Your Privacy Choices
This is a member-feature!
Sign up for free to view article comments.
We'd love to hear from you! Please share your name and email to post and read comments.
You'll also get the latest articles directly to your inbox.