Hereditary Angioedema

What is Hereditary Angioedema?

Hereditary angioedema is a rare genetic disorder that causes sudden, severe swelling in different parts of your body. The swelling happens because your body does not produce enough of a protein called C1 inhibitor, or the protein does not work correctly. This protein normally keeps your immune system balanced and prevents unwanted swelling.

When C1 inhibitor levels are low or not working, another part of your immune system called the complement system becomes overactive. This leads to the release of substances that cause blood vessels to leak fluid into surrounding tissues. The result is painful, unpredictable swelling episodes that can affect your face, throat, stomach, hands, feet, and other areas.

This condition affects roughly 1 in 50,000 people and runs in families. Episodes can be triggered by stress, illness, injury, or dental procedures, but sometimes they happen without any clear reason. The swelling typically lasts 2 to 5 days and then goes away on its own, but it can be dangerous if it blocks your airway.

Complement Component C3c

Reveal immune system issues effortlessly
Diagnose inflammation causes with precision
Clarify unexplained symptoms quickly

^$72

Complement Component C4c

Pinpoint the cause of unexplained inflammation
Reveal hidden immune system issues
Clarify the source of chronic fatigue

^$177

Complement Component C3c and C4c

Pinpoint the cause of unexplained inflammation
Reveal underlying immune system issues
Clarify the reasons for frequent infections

^$228

Symptoms

Sudden swelling of the face, lips, tongue, or throat
Swelling in the hands, feet, or genitals
Severe abdominal pain and cramping from intestinal swelling
Nausea, vomiting, or diarrhea during abdominal attacks
Difficulty breathing or swallowing if the throat swells
Skin tightness or tingling before swelling begins
Non-itchy skin swelling that does not respond to antihistamines
Hoarse voice during throat swelling episodes

Some people experience warning signs like tingling or skin tightness before swelling starts. Episodes can range from mild to life threatening depending on where swelling occurs. Throat swelling is a medical emergency that requires immediate treatment.

Causes and risk factors

Hereditary angioedema is caused by mutations in genes that control the production or function of C1 inhibitor protein. Most commonly, the SERPING1 gene is affected, leading to low levels of C1 inhibitor or a version that does not work properly. Because this is a genetic condition, you inherit it from one or both parents. If one parent has the condition, each child has a 50 percent chance of inheriting it.

Specific triggers can bring on swelling episodes even though the underlying cause is genetic. Common triggers include physical trauma, dental work, infections, stress, certain medications, hormonal changes, and menstruation. Some episodes happen without any identifiable trigger. The severity and frequency of attacks vary widely, even among family members with the same genetic mutation.

How it's diagnosed

Diagnosing hereditary angioedema requires specialized blood tests that measure complement system components. Doctors typically check levels of C1 inhibitor protein, C4 complement component, and C3 complement component. Low levels of C4 are a strong indicator of this condition because the overactive complement system depletes these proteins. Some tests also measure how well your C1 inhibitor protein functions, not just how much you have.

Your doctor will also take a detailed family history since this condition runs in families. Genetic testing can identify the specific mutation causing the condition. Because hereditary angioedema is rare, it is often misdiagnosed as allergies or other conditions at first. Talk to our doctor about specialized testing if you have recurrent unexplained swelling that does not respond to allergy medications.

Treatment options

Acute attack medications that replace C1 inhibitor or block swelling pathways
Preventive medications taken regularly to reduce attack frequency
Short-term preventive treatment before dental work or surgery
Emergency medications you can keep at home for sudden attacks
Avoiding known triggers like certain medications and unnecessary trauma
Wearing medical alert identification in case of emergencies
Working with an immunologist or allergist experienced in this condition
Regular monitoring of complement levels and treatment effectiveness

Frequently asked questions

Hereditary angioedema is caused by a genetic deficiency of C1 inhibitor protein, not an allergic reaction. The swelling does not itch, does not cause hives, and does not respond to antihistamines or epinephrine. It typically lasts longer than allergic swelling, usually 2 to 5 days, and can occur without any allergen exposure.

This condition follows an autosomal dominant pattern, meaning you only need one mutated gene copy to have the condition. If one parent has hereditary angioedema, each child has a 50 percent chance of inheriting it. About 25 percent of cases occur from new mutations with no family history.

Yes, swelling in the throat or larynx can block your airway and become life threatening if not treated quickly. Abdominal attacks can be extremely painful and sometimes lead to unnecessary surgeries if misdiagnosed. This is why early diagnosis and having emergency medications available is critical for people with this condition.

Doctors measure C1 inhibitor protein levels and function, along with C4 and C3 complement components. Low C4 levels are typically the first clue since the overactive complement system depletes this protein. Your doctor may also order genetic testing to identify the specific mutation causing the condition.

Attack frequency varies widely from person to person. Some people have attacks weekly, while others go months or years between episodes. The average is about one attack per month without preventive treatment. Frequency can change over time and may be influenced by stress, hormones, and other factors.

Several medications can treat acute attacks by replacing C1 inhibitor or blocking the pathways that cause swelling. These include C1 inhibitor concentrate, icatibant, and ecallantide. Many patients keep emergency medications at home so they can treat attacks immediately when they start.

Preventive medications can significantly reduce attack frequency and severity. Options include C1 inhibitor replacement therapy, androgen medications, and newer targeted therapies. Short-term prevention is also recommended before dental procedures or surgeries that might trigger an attack.

Yes, children should be diagnosed early and have an emergency action plan in place. Schools and caregivers need to know about the condition and warning signs of throat swelling. Many children start preventive treatment to reduce attacks and allow normal participation in activities.

Yes, emotional stress and anxiety are common triggers for swelling episodes. Physical stress like illness, injury, or surgery can also trigger attacks. While you cannot avoid all stress, managing stress through healthy lifestyle habits may help reduce attack frequency.

There is currently no cure since it is a genetic condition. However, modern treatments can effectively control symptoms and prevent most attacks. With proper medication and monitoring, most people with hereditary angioedema can live normal, active lives with minimal interruption from swelling episodes.