Acquired Angioedema vs. Hereditary Angioedema: Key Differences

Medically reviewed by Sterling Slocum, M.D.

Written by Kacie Riggs

Posted on July 8, 2026

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Key Takeaways

Hereditary angioedema (HAE) and acquired angioedema (AAE) are two rare conditions that can cause sudden, frightening swelling in the face, lips, throat, and other parts of the body, and understanding the differences between them can help people get the right diagnosis and care.

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Sudden swelling in your face, lips, or throat can feel scary and confusing, especially when it does not seem to be caused by an allergy. Two rare conditions called hereditary angioedema (HAE) and acquired angioedema (AAE) can cause this type of swelling. They may look similar, but they are not the same.

Knowing the differences between HAE and AAE can help people get the right diagnosis, avoid treatments that may not work, and feel more prepared to handle symptoms.

What Happens During a Swelling Episode?

Angioedema is a term that describes swelling in deeper layers of the skin or tissues under the skin. It often affects areas like the face, lips, tongue, throat, abdomen, or genitals. Angioedema happens when fluid leaks from tiny blood vessels and builds up in nearby tissues.

🗳️ Which condition were you diagnosed with?

Acquired angioedema

Hereditary angioedema

I’m not sure

In the most common types of HAE and in AAE, swelling happens because of a problem with a blood protein called C1 inhibitor. This protein helps control parts of the immune system and helps keep fluid from leaking out of blood vessels.

When C1 inhibitor doesn’t work properly, the body can make too much bradykinin. Bradykinin is a chemical that makes blood vessels leaky. This lets fluid move into nearby tissues, causing swelling.

Sometimes, allergies can also cause angioedema. But swelling from HAE and AAE isn’t caused by allergies. It also usually doesn’t involve hives, itching, or anaphylaxis. Anaphylaxis is a severe allergic reaction that can be life-threatening.

What Is HAE?

Hereditary angioedema is a genetic condition often passed down in families. It happens when a person inherits a mutation (gene change) or has a random mutation that affects the C1 inhibitor protein.

HAE causes angioedema because the body either makes too little C1 inhibitor (type 1 HAE) or makes a version of the protein that doesn’t work correctly (type 2 HAE). In rarer cases, people can have HAE even when their C1 inhibitor levels and function are normal.

Symptoms of HAE often begin during childhood or the teenage years, and those who have HAE usually have a family history of the condition.

What Is AAE?

Acquired angioedema is similar to HAE, but it isn’t inherited. Instead, AAE usually develops later in adulthood. It may happen when the body makes antibodies that attack C1 inhibitor or when another health condition causes C1 inhibitor to be used up or broken down.

These health conditions may include a blood or lymph disorder or an autoimmune disease. In autoimmune diseases, the immune system mistakenly attacks the body’s own tissues.

Why HAE and AAE Are So Easy To Confuse

HAE and AAE can look almost identical.

Both conditions include shared symptoms like:

Sudden swelling of the face, lips, and tongue
Swelling of the hands, feet, or genitals
Trouble breathing due to swelling in the upper airway
Abdominal pain, nausea, or vomiting from swelling in the digestive tract
Episodes that can last for days at a time

Unlike allergic reactions, HAE and AAE attacks usually don’t cause hives or itching. Antihistamines, corticosteroids, and epinephrine usually don’t help these attacks.

Both HAE and AAE attacks can be triggered by injuries, dental work, infections like the flu, or stress. Triggers are different for everyone, and sometimes, you may not even be able to tell what caused an attack.

Because the symptoms and potential triggers overlap so much, doctors rely on a person’s medical history and blood tests to tell the two conditions apart. Sometimes, genetic testing is also used to look for mutations responsible for HAE.

How To Tell HAE and AAE Apart

Although the symptoms are similar, some clues can help doctors tell HAE and AAE apart.

When Symptoms Start

Symptoms of HAE can begin as early as 2 years old, and most people will show symptoms by age 20.

AAE typically begins later in adulthood, often after age 40.

Family History

Because HAE is genetic, it often runs in families. In some cases, the genetic mutation can happen on its own, without a family history of HAE.

On the other hand, AAE isn’t caused by genetic changes, so there’s usually no family history of the disorder.

Associated Conditions

HAE isn’t tied to other diseases, and people are often otherwise healthy. But AAE is commonly linked to blood cancers or autoimmune diseases.

Lab Findings

Blood tests are one of the most helpful ways healthcare providers can tell HAE and AAE apart.

In both HAE and AAE, C1 inhibitor levels and C4 levels are often low. C4 is a type of protein found in the blood. C4 levels are used to determine how well the body’s immune system is working.

One key difference between the two conditions involves C1q, another immune system protein found in the blood. In people with HAE, C1q levels are usually normal. In people with AAE, these levels are often low.

A low C1q level generally suggests AAE and helps doctors and HAE specialists tell it apart from HAE.

Managing HAE and AAE Attacks

Treatment for HAE and AAE focuses on stopping the swelling attacks quickly and preventing future attacks.

Both conditions can usually be treated with on-demand medications that address symptoms once they start. These may include:

C1 inhibitor replacement therapy, which adds working C1 inhibitor to the body
Bradykinin receptor blockers, which block the effects of bradykinin, a chemical that causes swelling
Kallikrein inhibitors, which help lower bradykinin levels and reduce swelling

Newer HAE treatments have also given people more ways to treat attacks when they happen and help prevent future attacks. These include oral and injectable medicines.

Preventive medications may also keep symptoms from starting and reduce the risk of an attack.

For AAE specifically, treatment often also involves finding and treating the underlying cause, such as an autoimmune condition or a blood or lymph disorder. Some medicines used for HAE may also be used for AAE, but there is less research on AAE treatment.

Neither HAE nor AAE is caused by allergies. Because of this, allergy medications like antihistamines or epinephrine don’t help with symptoms. They shouldn’t be used as part of a treatment plan.

Why Getting the Right Diagnosis Matters

Telling HAE and AAE apart is important because the two conditions have different causes.

AAE may also signal that an underlying health condition needs treatment. Treating the underlying cause may help reduce the chance that attacks will happen again.

Even though both conditions are rare, patterns such as when symptoms start and whether the condition runs in the family can help healthcare providers make the right diagnosis.

When To Get Emergency Care

Both HAE and AAE can cause swelling in the upper airway, which can make it hard to breathe or swallow. This type of swelling can become life-threatening very quickly and requires immediate emergency care.

Finding the Right Diagnosis

HAE and AAE can feel very similar. Understanding the differences between the two conditions, especially when symptoms start, family history, and lab results, can help guide the right diagnosis and care plan.

If you’re living with angioedema or still searching for answers, working with a specialist and getting the right testing can make a big difference in managing symptoms and protecting your health.