Hereditary angioedema explained

What hereditary angioedema is

Hereditary angioedema, often shortened to HAE, is a rare condition passed down through families. In most people with it, the body is short of, or has a faulty version of, a protein in the blood that normally keeps a particular chemical pathway in check. Without enough of this control protein, a substance called bradykinin can build up. Bradykinin makes small blood vessels leaky, so fluid seeps into the tissues and causes swelling. Because a single altered gene is usually enough to cause it, a parent with HAE has a good chance of passing it on, and there is often a family history of unexplained swelling attacks. It is important to know that HAE is not an allergy and not caused by anything the person has eaten or done wrong.

How attacks present

Attacks of hereditary angioedema come and go and can affect different areas. Swelling may appear in the hands, feet, arms, legs, face, lips or genitals, often building up over several hours and then settling over a day or two. When the swelling affects the bowel wall, it causes attacks of severe tummy pain, cramping, and sometimes vomiting, which can be mistaken for other causes of a bad stomach. The most serious attacks involve the throat and airway, where swelling can make breathing and swallowing difficult and become life-threatening. Unlike allergic swelling, HAE attacks are usually not itchy and often do not come with a raised, red hives rash. Some people notice a warning tingling or a blotchy skin pattern before an attack begins, giving them a little time to act.

Why it is not the same as allergy

It is easy to confuse hereditary angioedema with a severe allergic reaction, because both cause swelling, but the mechanisms are different and this matters for treatment. Allergic swelling is driven by histamine and often comes with itching, hives and sometimes a rapid, whole-body reaction; it responds to antihistamines, steroids and adrenaline. HAE swelling is driven by bradykinin, is usually not itchy, and typically does not respond well to those allergy treatments. Instead, HAE needs specific medicines that target the bradykinin pathway. This is why an accurate diagnosis is so important: someone having an HAE airway attack needs the right specialist treatment, and knowing they have HAE rather than an allergy ensures the emergency team and the person use the correct emergency plan.

How it is diagnosed

Hereditary angioedema is often suspected when someone has repeated swelling attacks that are not itchy, do not respond to allergy treatments, and especially when there is a family history of similar problems. Diagnosis is confirmed with blood tests that measure the level and activity of the control protein involved and related markers in the blood. Because the condition is rare, people are usually referred to a specialist centre, often an immunology or allergy service, which can confirm the diagnosis, test family members if appropriate, and set up a proper management plan. Getting a firm diagnosis can be a relief after years of unexplained attacks, and it opens the door to the specific treatments and emergency planning that make HAE much safer to live with.

Preventing and treating attacks

Care for hereditary angioedema is led by a specialist team and has two parts: treating attacks and preventing them. Specific medicines are available to treat acute attacks, particularly those affecting the airway or gut, and people are usually given a clear emergency plan and, where appropriate, treatment they or the emergency services can use quickly. Some people also take regular preventive treatment to reduce how often attacks happen, especially if attacks are frequent or severe. Avoiding known triggers, such as certain medicines that can worsen swelling, and telling doctors and dentists about the diagnosis before procedures, all help. Wearing medical alert identification and carrying an emergency plan are valuable, because a throat attack is an emergency. With specialist care, most people with HAE can lead full lives.