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Understanding hereditary angioedema

Q: What is hereditary angioedema (HAE)?

A: People suffering from HAE have a low level of an important protein in their blood. The protein is called C1-INH (pronounced “C1 inhibitor,” which is short for “complement 1 esterase inhibitor”). C1-INH regulates and “turns off” various reactions in the body. In people with HAE, a low level or decreased function of C1-INH is thought to be the major reason for recurrent, often severe, and even life-threatening swelling (angioedema) in different parts of the body. There are two major types of HAE. Type I is caused by low levels of C1-INH. Type II is caused by a decreased function of some of the C1-INH protein. Recently, another kind of HAE (type III) has been identified. In these patients, C1-INH levels are usually normal. Learn more about types of HAE.

Q: How serious is HAE?

A: The severity of HAE is determined by the frequency, location, and degree of swelling. Swelling in the throat may compromise the airway. Therefore, these attacks of HAE can be life-threatening. Swelling in the intestines may cause severe abdominal pain and discomfort. Although the majority of the attacks are not life-threatening, they can seriously affect quality of life. Find out more about living with HAE.

Q: How does a person get HAE?

A: HAE is usually inherited. The abnormality in the C1-INH gene is passed down from a parent to a child. However, about 25% to 30% of HAE cases are caused by a new mutation. In these cases, there is no previous history of HAE in the family. If someone with HAE has a child with a person without the condition, there is a 50% chance their child will have HAE. Learn about what causes HAE.

Q: What are the symptoms of HAE?

A: HAE may mimic other types of medical conditions, such as allergic reactions or appendicitis. However, there are some clues that help physicians identify HAE and distinguish it from other medical problems. The eight simple questions can help you and your physician differentiate HAE from other medical problems.

Q: Since HAE is hereditary, will I pass HAE to my children?

A: If you have HAE and your partner does not, each of your children has a 50-50 chance of inheriting HAE. Learn about what causes HAE.

Q: How common is HAE?

A: Only about 1 in 10,000 to 50,000 people has HAE.

Q: How is HAE diagnosed?

A: HAE is diagnosed by taking a blood sample and measuring the level of C1-INH in the blood. C4 (another important blood protein) is often used in screening tests. Type I HAE is diagnosed by confirming a low level of C1-INH. People with type II HAE will have a normal C1-INH level, but an abnormal C1-INH functional level. No single test can diagnose type III HAE.

Managing hereditary angioedema

The following information does not replace or substitute consultation by a physician and medical advice should always be sought.

Q: Are there any warning signs that may help tell me I am going to have an attack?

A: Attacks are often unpredictable, but you may be able to sense their onset. You will learn to recognise symptoms that herald an attack for you. Common symptoms are sudden mood changes, rash, irritability, aggressiveness, anxiety, extreme fatigue, or a tingling sensation of the skin where the swelling will begin. These symptoms are called prodrome or prodromal symptoms. A hoarse voice or laryngitis, difficulty in swallowing, a feeling of tightness, and voice changes may be the first signs of a life-threatening laryngeal attack. If you experience these symptoms should get emergency help as soon as possible. Learn more about identifying serious attacks.

Q: Should I be on a special diet?

A: There is no evidence at this time to suggest that changes in diet, exercise, or lifestyle will impact the frequency of HAE attacks. Learn more about living with HAE.

Q: Where can I find out about a support group for HAE families?

A: There is a support group available to families with HAE. HAE UK is an association of HAE patients, working together to improve the situation for all HAE Patients in the UK. Visit

Q: Can stress cause HAE attacks?

A: Although actual causes of HAE attacks have not been established and vary from patient to patient, some patients report an increased number of attacks during and after stressful situations. By tracking your symptoms carefully and keeping a journal, you can discover whether or not stress is a trigger for you. Learn more about identifying potential triggers of HAE.

Q: Are there specific medications that may trigger HAE attacks?

A: Patient histories reveal that medications and contraceptives containing oestrogen may trigger HAE attacks or increase attack frequency. In addition, blood pressure lowering medications known as ACE inhibitors can provoke attacks. For this reason, doctors may prescribe an alternative blood pressure lowering medication. Additionally, patients may have individual sensitivities to various medications. Before taking any new medications you should always consult a doctor about potential interactions.

Treating hereditary angioedema

Q: What should I do if I have a hereditary angioedema (HAE) attack?

A: People who experience symptoms of a laryngeal attack (swelling of the larynx, or voice box) should get emergency help as soon as possible. A doctor who is an expert on HAE can help you determine what you should do when you have an attack. The prescribed course of treatment may depend on the location of the attack, the frequency of attacks and the type of medications available to you. Learn more about treating an acute attack of HAE.

Q: How are acute HAE attacks treated?

A: For acute attacks, there are currently the following treatment options available: C1-INH, bradykinin inhibitor and recombinant C1 esterase inhibitor. Learn more about treatment options for HAE.

Q: What side effects might I have with treatment, and how do I manage them?

A: The side effects you experience will depend on the treatment option used, the dosage and how the treatment is administered.

Talk to your doctor about potential side effects based on your personal treatment and when you should call the doctor about a medical problem. Recording information in a diary will help you and your doctor track your progress and effectively manage your condition.

Reporting of side effects of medication: If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in the package leaflet. You can also report side effects directly via the Yellow Card Scheme at .

By reporting side effects you can help provide more information on the safety of your medicine.

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