What Is Hereditary Angioedema? Recurrent Swelling, Causes & Treatment Options

Hereditary angioedema is a group of rare genetic disorders that cause unpredictable episodes of deep swelling beneath the skin or within mucosal tissues. HAE attacks often affect the hands, feet, face, lips, eyelids, genitals, gastrointestinal tract, tongue, throat and upper airway.

Most classic forms involve deficient or dysfunctional C1 inhibitor, allowing excessive bradykinin-mediated vessel leakage. Abdominal attacks may cause severe pain without visible swelling, while tongue or laryngeal attacks can obstruct breathing and require immediate on-demand treatment plus emergency airway assessment.

Which Deep Swelling Does Hereditary Angioedema Describe?

Hereditary angioedema describes inherited, recurrent bradykinin-mediated swelling with specific diagnostic, emergency and preventive treatment needs.

The broader term angioedema describes deeper skin or mucosal swelling from several possible mechanisms, including allergy, medicines, acquired C1-inhibitor deficiency and hereditary pathways.

HAE is not ordinary allergic swelling. It usually occurs without typical itchy hives and can involve the bowel or upper airway.

How Can You Recognize a Hereditary Angioedema Attack?

A hereditary angioedema attack usually causes deep, tight swelling without the typical itchy hives seen in many allergic reactions.

The affected area may feel heavy, pressured or painful and usually shows little pitting when pressed. Hands or feet may become difficult to use, facial features can distort temporarily and genital swelling can impair movement.

Severe abdominal pain may occur without external swelling. Attacks can build over hours, persist for days untreated and recur in different locations over months or years.

Poor response to antihistamines or corticosteroids supports a bradykinin pathway but does not establish the diagnosis.

• Recurrent deep swelling.
• Little or no ordinary itching.
• No typical urticarial wheals.
• Tightness, pressure or pain.
• Limb, face, genital, abdominal or airway involvement.
• Longer duration than ordinary hives.
• Weak response to allergy-directed medicines.

What Should You Do When an HAE Attack Begins?

When an HAE attack begins, use the prescribed on-demand HAE medicine at the earliest recognized symptom.

• Treat early according to the individual plan.
• Check immediately for tongue, throat, voice, swallowing or breathing involvement.
• Call emergency services for possible upper-airway swelling.
• Do not wait for the attack to become severe.
• Carry the backup treatment specified in the plan.
• Continue monitoring because symptoms can progress or recur.
• Tell emergency clinicians that the swelling may be bradykinin-mediated HAE.
• Document attack location, trigger, treatment and response.

Any attack affecting or potentially affecting the upper airway requires immediate treatment and emergency assessment.

Which Parts of the Body Can Hereditary Angioedema Affect?

HAE can affect the hands, feet, arms, legs, face, lips, eyelids, tongue, throat, genitals, bowel and upper airway.

Attacks are usually localized rather than generalized whole-body fluid accumulation. Temporary vessel leakage can affect one region during one episode and a different region during the next.

How Does HAE Swelling Affect the Hands, Feet and Face?

HAE swelling in the hands, feet or face often feels tight, heavy and painful rather than itchy.

One hand, foot or larger part of a limb can enlarge enough to prevent gripping, walking or wearing shoes. Facial attacks can produce asymmetry and marked lip or eyelid swelling.

The skin may appear normal, mildly red or stretched. Absence of hives helps distinguish HAE from many mast-cell reactions, but appearance alone is not diagnostic.

How Does an Abdominal HAE Attack Feel?

An abdominal HAE attack can cause severe cramping, vomiting or diarrhea even when no external swelling is visible.

Pain may be colicky and come in waves. Bowel-wall edema and fluid shifting can cause nausea, abdominal distension, appetite loss, dehydration and light-headedness.

The episode may resemble appendicitis, obstruction or another surgical emergency. Recurrent unexplained attacks, especially with transient bowel edema or free fluid on imaging, should raise suspicion for HAE.

Which Throat and Airway Symptoms Make HAE an Emergency?

Tongue, throat, voice, swallowing or breathing symptoms during HAE are medical emergencies.

• Tongue swelling.
• Throat tightness or a lump sensation.
• Difficulty swallowing.
• Drooling or inability to handle saliva.
• Hoarse or altered voice.
• Noisy breathing or stridor.
• Neck swelling.
• Shortness of breath.
• Rapid progression of mouth or facial swelling.

Use prescribed on-demand medicine immediately, call emergency services and prepare for airway protection. Do not remain at home waiting for spontaneous improvement.

Can HAE Cause Warning Symptoms Before Visible Swelling?

Some people notice warning symptoms before swelling becomes obvious, but not every person has a reliable prodrome.

Possible warnings include tingling, tightness, local discomfort, fatigue, irritability, mood change, nausea and muscle aching.

Erythema marginatum is a flat, usually non-itchy expanding ring-like rash that may occur before or during an attack and can be mistaken for hives.

Target-like painful or blistering lesions should not be confused with erythema multiforme without clinical assessment.

How Does Hereditary Angioedema Develop Inside the Body?

HAE develops when contact-system regulation fails and excess bradykinin makes blood vessels temporarily leaky.

C1 inhibitor regulates complement, contact, clotting and fibrinolytic pathways. Deficiency or dysfunction allows greater factor XII and plasma-kallikrein activity.

Kallikrein releases bradykinin from high-molecular-weight kininogen. Bradykinin binds B2 receptors on vessel cells, increasing permeability and allowing fluid to enter subcutaneous or mucosal tissue.

This mechanism produces localized deep swelling without the histamine-driven hive pattern typical of many allergies.

What Causes Hereditary Angioedema?

HAE is caused by inherited or newly occurring pathogenic genetic variants that affect swelling-control pathways.

The most common forms involve SERPING1, which provides instructions for C1 inhibitor. A variant can reduce the amount of C1 inhibitor or impair its function.

About one quarter of HAE-C1-INH cases may result from a new de novo variant rather than a previously recognized affected parent.

HAE is not caused by poor hygiene, infection, contagion or food allergy. A trigger can start an attack but does not create the underlying genetic disorder.

How Is Hereditary Angioedema Inherited?

HAE caused by C1-inhibitor deficiency or dysfunction is usually inherited in an autosomal dominant pattern.

One altered gene copy can cause disease. An affected parent has a 50% probability of passing the familial variant to each child, and the probability resets with every pregnancy.

Severity can differ greatly within the same family. Absence of known family history does not exclude HAE because de novo variants and unrecognized symptoms occur.

Which Types of Hereditary Angioedema Affect C1 Inhibitor?

What Is HAE With Low C1-Inhibitor Levels?

HAE with low C1-inhibitor levels is the traditional type I form of HAE-C1-INH.

C1-INH protein quantity and function are reduced, and complement C4 is often low. A pathogenic SERPING1 variant is usually responsible.

What Is HAE With Dysfunctional C1 Inhibitor?

HAE with dysfunctional C1 inhibitor is the traditional type II form of HAE-C1-INH.

The amount of C1-INH may be normal or elevated, but its function is reduced and C4 is often low. Modern guidance groups both patterns under HAE-C1-INH because the clinical approach is substantially shared.

What Is Hereditary Angioedema With Normal C1 Inhibitor?

HAE with normal C1 inhibitor describes recurrent hereditary swelling despite normal C1-INH amount and function.

Reported genetic forms include F12, PLG, ANGPT1, KNG1, MYOF, HS3ST6, CPN1 and DAB2IP, while some families have no currently identifiable variant.

Facial, tongue or airway attacks and estrogen sensitivity may be prominent in selected subtypes. Diagnosis requires a structured exclusion of mast-cell-mediated, medication-induced and acquired angioedema.

Normal C1-INH and C4 do not establish this diagnosis by themselves.

Which Factors Can Trigger an HAE Attack?

HAE attacks can follow trauma, procedures, pressure, infection, stress, hormones or medicines, but many attacks have no clear trigger.

• Minor injury or repetitive pressure.
• Dental procedures.
• Surgery, endoscopy or airway instrumentation.
• Infection.
• Emotional stress or sleep loss.
• Menstruation or pregnancy-related hormonal change.
• Estrogen-containing contraception or hormone therapy.
• ACE-inhibitor exposure.
• No identifiable trigger.

Trigger tracking supports procedure planning but should not be used to blame a patient for unpredictable attacks.

How Is HAE Different From Allergic Angioedema?

HAE is usually bradykinin-mediated, slower and longer-lasting, without ordinary itchy hives.

An undiagnosed airway emergency may be anaphylaxis, HAE or another process. Emergency clinicians may treat possible anaphylaxis while protecting the airway and evaluating bradykinin-mediated swelling.

How Is HAE Different From ACE-Inhibitor Angioedema?

HAE is an inherited recurrent disorder, while ACE-inhibitor angioedema is a medication-related bradykinin reaction.

ACE-inhibitor swelling commonly affects lips, tongue, face or airway and can begin after the medicine has been used for a long time. It does not require family history and C1-INH tests are usually normal.

The ACE inhibitor should be permanently discontinued under medical guidance. ACE inhibitors are also generally avoided in confirmed HAE.

How Is HAE Different From Acquired C1-Inhibitor Deficiency?

Acquired C1-inhibitor deficiency usually begins later in adulthood and is linked to another disease rather than inherited HAE.

C1q and C1-INH autoantibody testing can help when late onset or associated systemic disease suggests an acquired process.

Which Other Conditions Can Resemble Hereditary Angioedema?

Several allergic, medication-related, infectious, systemic and gastrointestinal disorders can resemble HAE.

Localized swelling after a clear exposure may suggest allergic contact dermatitis, especially when itching and surface inflammation match the contact area.

One-sided painful swelling with warmth, fever, tenderness or spreading redness may suggest cellulitis rather than a typical HAE attack.

How Do Clinicians Diagnose Hereditary Angioedema?

Clinicians diagnose HAE by combining the swelling pattern with complement and C1-inhibitor testing.

• Recurrent non-itchy swelling without ordinary hives.
• Abdominal or airway episodes.
• Age at first attack and attack duration.
• Trigger and medication history.
• Family pattern, while recognizing it may be absent.
• Response to antihistamines or steroids.
• Estrogen exposure.
• C1-INH function, C1-INH level and C4.
• C1q or genetics when indicated.

De novo variants and unrecognized disease in relatives mean that family history supports diagnosis but is not required.

Which Blood Tests Are Used to Diagnose HAE-C1-INH?

The main blood tests are C1-INH function, C1-INH antigenic level and complement C4.

C1-INH function asks whether the protein regulates its target pathways; antigenic testing measures how much protein is present. C4 is often reduced but is not a stand-alone exclusion test.

C1q and C1-INH autoantibodies help investigate acquired deficiency. Abnormal results should be repeated for confirmation using reliable specialist assays.

When Is Genetic Testing Needed for Hereditary Angioedema?

Genetic testing helps when a familial variant is needed, biochemical results are uncertain or HAE with normal C1 inhibitor is suspected.

• Identify a familial SERPING1 variant for relative testing.
• Clarify uncertain biochemical results in a child.
• Investigate normal-C1-INH hereditary swelling.
• Assess strong family pattern with normal complement testing.
• Resolve conflicting clinical and laboratory findings.
• Support prenatal or preimplantation planning.
• Help distinguish hereditary from acquired disease.

A negative panel does not exclude every hereditary form because not all mechanisms are currently identifiable.

Should Family Members Be Tested After an HAE Diagnosis?

First-degree relatives should be offered appropriate evaluation after an HAE diagnosis is confirmed.

Testing can identify relatives before a first airway attack. Children of an affected parent have a meaningful inherited risk, while infant laboratory results may require age-appropriate interpretation.

When a familial variant is known, targeted genetic testing can complement biochemical assessment. Confirmed relatives need treatment access, emergency education and a written action plan.

Does Every HAE Attack Require On-Demand Treatment?

Every HAE attack should be considered for early on-demand treatment, and any upper-airway attack must be treated immediately.

Face, neck and significant abdominal attacks generally justify prompt treatment. A previously mild disease course does not guarantee that a future throat attack will remain mild.

Long-term prophylaxis does not eliminate the need for rescue medicine.

Which Medicines Treat an Acute Hereditary Angioedema Attack?

How Does C1-Inhibitor Concentrate Treat an Attack?

C1-inhibitor concentrate replaces missing or dysfunctional regulation and reduces uncontrolled contact-system activation.

Plasma-derived intravenous products and recombinant C1 inhibitor in selected regions can treat peripheral, abdominal, facial and airway attacks. Self-administration requires training and local authorization.

How Does Icatibant Treat an Attack?

Icatibant blocks the bradykinin B2 receptor and limits continued vascular leakage.

It is given subcutaneously; age approvals and repeat-treatment rules vary by country and the individual plan.

How Does Ecallantide Treat an Attack?

Ecallantide inhibits plasma kallikrein.

In the United States it is administered by a healthcare professional because serious hypersensitivity, including anaphylaxis, can occur.

How Does Oral Sebetralstat Treat an Attack?

Sebetralstat is an oral plasma-kallikrein inhibitor used at early attack recognition.

The FDA approved EKTERLY in July 2025 for acute HAE attacks in adults and patients aged 12 years and older. Availability, interactions and clinical eligibility vary by country.

What Happens When Standard On-Demand HAE Medicine Is Unavailable?

When targeted on-demand medicine is unavailable, emergency care should follow a specialist protocol and still prioritize airway protection.

Solvent-detergent-treated plasma or fresh frozen plasma may be considered when HAE-specific products cannot be accessed, but they carry transfusion and volume risks and are not equivalent first choices.

Patients should build an access plan before emergencies, especially when travelling or living far from specialist centres.

Why Do Antihistamines, Steroids and Epinephrine Usually Fail to Stop HAE?

Antihistamines, corticosteroids and epinephrine usually fail to stop confirmed HAE because they do not directly block the bradykinin pathway.

Antihistamines block histamine, steroids broadly suppress inflammation and epinephrine is lifesaving for anaphylaxis, but none directly replaces C1-INH or stops excessive kallikrein activity.

Repeated allergy treatment without response should prompt diagnostic reconsideration. Suspected anaphylaxis remains an emergency and may still require epinephrine while clinicians protect the airway and identify the mechanism.

How Is an Upper-Airway HAE Attack Managed in Hospital?

Hospital care combines immediate HAE-specific medicine with early preparation for definitive airway protection.

• Immediate on-demand HAE medicine.
• Continuous airway and oxygen assessment.
• Early difficult-airway expertise.
• Fiber-optic or advanced-airway equipment preparation.
• Early intubation when obstruction is progressing.
• Surgical-airway readiness if intubation is impossible.
• Observation after initial improvement.
• Repeat treatment according to product guidance and clinical response.

Medication can reduce swelling, but advanced obstruction may progress too quickly to wait for drug response. Airway patency remains the first priority.

How Are Attacks Prevented Before Dental, Surgical or Medical Procedures?

Selected dental, surgical and airway procedures require short-term prophylaxis planning with the HAE specialist.

Tooth extraction, oral surgery, intubation, bronchoscopy, upper endoscopy and head or neck procedures can trigger attacks through tissue trauma.

• Notify the HAE team before the procedure.
• Assess previous procedure reactions and airway risk.
• Use specialist-recommended short-term prophylaxis.
• Plasma-derived C1-INH is a preferred preprocedural option in international guidance.
• Keep on-demand treatment immediately available.
• Use an airway-capable setting for high-risk procedures.
• Observe after the procedure when delayed swelling is possible.

Prophylaxis reduces but does not eliminate procedure-related risk.

Who Should Consider Long-Term Preventive Treatment?

Long-term prophylaxis should be considered according to disease burden, airway risk, access to emergency care and patient goals rather than a rigid attack count alone.

• Attack frequency and severity.
• History of airway involvement.
• Abdominal-attack burden.
• Emergency or rescue-treatment use.
• School, work or sleep disruption.
• Travel or remote-care risk.
• Anxiety and caregiver burden.
• Quality-of-life impairment.
• Response and burden of on-demand therapy.
• Pregnancy plans and patient preferences.

The goal is complete or near-complete disease control with meaningful quality-of-life improvement. Preventive treatment should be reassessed regularly.

Which Treatments Can Prevent Recurrent HAE Attacks?

How Does Subcutaneous C1-Inhibitor Replacement Prevent Attacks?

Regular subcutaneous C1-INH replacement maintains protective regulatory activity in HAE-C1-INH.

It requires injection training, supply continuity and consideration of local injection reactions.

How Does Lanadelumab Prevent Attacks?

Lanadelumab is a subcutaneous monoclonal antibody that inhibits active plasma kallikrein.

Approved ages and schedules vary by country, and rescue medicine remains necessary.

How Does Berotralstat Prevent Attacks?

Berotralstat is a regular oral plasma-kallikrein inhibitor used for prevention rather than acute rescue.

Gastrointestinal effects and drug interactions can influence suitability.

How Does Garadacimab Prevent Attacks?

Garadacimab targets activated factor XII higher in the contact-system cascade.

The FDA approved ANDEMBRY in June 2025 as a monthly subcutaneous preventive treatment for patients aged 12 years and older.

How Does Donidalorsen Prevent Attacks?

Donidalorsen is an antisense medicine that reduces liver production of prekallikrein.

The FDA approved DAWNZERA in August 2025 for prophylaxis in adults and patients aged 12 years and older.

Are Androgens or Tranexamic Acid Still Used to Prevent HAE Attacks?

Attenuated androgens and tranexamic acid remain options in selected settings, but modern targeted prophylaxis is generally preferred when accessible and suitable.

Danazol can increase C1-INH production but can cause androgenic, metabolic, cardiovascular and liver adverse effects and requires monitoring. It is unsuitable during pregnancy and for many children.

Tranexamic acid has weaker and less consistent preventive evidence. Neither medicine replaces effective on-demand treatment.

Can HAE Attacks Occur Despite Long-Term Prophylaxis?

Breakthrough HAE attacks can occur during prophylaxis, so every patient still needs on-demand rescue medicine.

Any breakthrough airway attack remains an emergency. Attack frequency, location, adherence, injection technique, interactions and rescue use should be reviewed.

Preventive dose intervals or treatment choice may be adjusted through shared decision-making.

How Is Hereditary Angioedema Managed During Pregnancy?

HAE during pregnancy requires a specialist plan because disease activity can improve, worsen or remain unchanged.

Medication plans should be reviewed before conception. Plasma-derived C1-INH is generally preferred for HAE-C1-INH attacks and for prophylaxis when needed during pregnancy.

Delivery planning should include rescue medicine and airway readiness. Attenuated androgens are contraindicated, newer medicines may have limited pregnancy evidence and breastfeeding plans require product-specific review.

How Is HAE Diagnosed and Treated in Children?

HAE can begin in childhood, so children in affected families need early recognition, testing and an emergency action plan.

Abdominal attacks may be mislabelled as infection or functional pain. Laboratory interpretation may vary with age, and medicine approvals differ by product and country.

• Offer family screening.
• Create home and school emergency plans.
• Train caregivers to recognize airway signs.
• Select age-appropriate rescue and preventive options.
• Consider body weight, developmental needs and route burden.
• Support gradual supervised self-treatment skills.
• Review school participation and quality of life.

Which Medicines or Hormones Can Worsen HAE?

ACE inhibitors and estrogen-containing medicines can worsen HAE or trigger bradykinin-mediated swelling in susceptible people.

A medication history matters because a drug rash, ACE-inhibitor angioedema or another medication reaction changes testing and emergency treatment.

ACE inhibitors are generally avoided in confirmed HAE. Progestin-only or non-hormonal contraception may be considered where appropriate, especially when estrogen sensitivity is suspected.

Do not stop essential treatment abruptly; coordinate alternatives with the prescriber and HAE specialist.

Which Hereditary Angioedema Management Mistakes Should Be Avoided?

The most dangerous mistakes are allergy-only treatment, waiting during airway symptoms and relying on prevention without rescue medicine.

How Should Someone Prepare for Travel, School or Work With HAE?

People with HAE should carry rescue medicine, an emergency plan and clear medical documentation.

• Carry sufficient on-demand treatment in hand luggage.
• Follow product storage requirements.
• Carry a written action plan and medical identification.
• Know the nearest emergency facility.
• Inform trusted school or workplace personnel.
• Keep specialist contact details available.
• Arrange travel insurance and medicine documentation.
• Train companions to recognize airway signs.
• Plan carefully for remote destinations.
• Document attacks and treatment response.

Preparation should support normal participation rather than unnecessary avoidance of everyday activity.

How Long Does an Untreated HAE Attack Last—and Can Attacks Change Over Time?

An untreated HAE attack often builds over several hours and may last for several days.

Attack frequency ranges from rare to frequent, and severity can change with puberty, pregnancy, estrogen exposure and other life stages.

One relative may have mild disease while another has severe attacks. A person without previous throat attacks still retains future airway risk, and long symptom-free periods do not mean cure.

Can Hereditary Angioedema Be Cured?

Current approved HAE medicines can treat or prevent attacks but do not permanently correct the inherited variant throughout the body.

Effective prophylaxis can greatly reduce attack burden and restore daily function, while on-demand therapy can shorten acute attacks.

Gene-silencing and gene-editing approaches are under investigation but should not be presented as available genetic cures.

How Does HAE Affect Quality of Life?

HAE can impair quality of life even when attacks are infrequent because swelling is unpredictable and airway episodes can be fatal.

Fear of suffocation, anxiety, missed school or work, interrupted sleep, travel avoidance, severe abdominal pain, dehydration, caregiver burden and treatment-access costs can be substantial.

Long-term prophylaxis decisions should consider life restriction and treatment burden, not only attack count.

When Is Hereditary Angioedema a Medical Emergency?

HAE is a medical emergency whenever swelling may involve the tongue, throat, voice, swallowing, breathing or upper airway.

• Tongue swelling.
• Throat tightness.
• Voice change.
• Difficulty swallowing or drooling.
• Noisy breathing or stridor.
• Shortness of breath.
• Rapidly increasing mouth or neck swelling.
• Inability to speak normally.
• Blue lips.
• Fainting or reduced responsiveness.
• Severe abdominal pain with persistent vomiting or dehydration.
• An attack that worsens after initial treatment.

Administer prescribed HAE-specific on-demand treatment immediately and obtain emergency care. Upper-airway symptoms require preparation for airway intervention.

What Should You Remember About Hereditary Angioedema?

Hereditary angioedema causes recurrent deep swelling driven mainly by bradykinin rather than histamine.

• HAE attacks usually occur without ordinary hives or significant itching.
• Hands, feet, face, genitals, intestines and airway can be affected.
• Tongue or throat swelling requires immediate treatment and emergency care.
• Classic HAE commonly involves deficient or dysfunctional C1 inhibitor.
• HAE-C1-INH is usually autosomal dominant, but de novo variants occur.
• C1-INH function, C1-INH amount and C4 are central tests.
• Normal C1 inhibitor does not exclude every hereditary form.
• Every attack should be considered for early on-demand treatment.
• Acute options include C1-INH, icatibant, ecallantide and sebetralstat where appropriate.
• Modern prevention targets C1-INH, kallikrein, factor XIIa or prekallikrein.
• Prophylaxis does not remove the need for rescue medicine.
• Family testing, procedure planning and written emergency plans protect patients and relatives.

What Questions Do People Ask About Hereditary Angioedema?

Which Sources Support This Hereditary Angioedema Guidance?