Angioedema

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What is Angioedema?

Angioedema is a reaction characterized by fluid accumulation leading to swelling (oedema) of the skin, mucosa and submucosal tissues. Sometimes this can extend to deeper tissues. Because of the rapid progression of the condition, it can lead to potential airway obstruction and suffocation. Hence, angioedema is treated as a medical emergency.

Angioedema is also known as angioneurotic oedema (older term). It can happen in different parts of the body, but the commonly affected part would be the face and the airways. Because of the swelling of the face, it can be extremely disfiguring and frightening to the patient.

Generally angioedema is characterised by involvement of the following sites:

face
airways, eg larynx (the voice box)
bowels

Who gets Angioedema?

Angioedema is considered to be a rare condition. There are many triggers identified that can cause angioedema. Sometimes the 'true' incidence of angioedema is overlapped with anaphylaxis, as it can be a premonitory or accompanying symptom to an anaphylactic or anaphylactoid reaction.

Amongst all trigger for angioedema, angiotensin converting enzyme (ACE) inhibitor would be the most notorious. ACE inhibitors are drugs used to treat high blood pressure, for example enalapril, perindopril, etc. Angioedema occurs in 0.1-0.7% of patients taking the medication. Although uncommon, because of the large number of patients treated with this class of drugs, this can become a significant cause of angioedema.

Predisposing Factors

There are 2 types of angioedema - hereditary and acquired. Hereditary means having the disease from birth due to genetic defect; while acquired means the disease is caused by external substances. Hereditary angioedema is transmitted from parents to children. All races are affected equally, and both males and females are equally affected too.

As for acquired angioedema, it is presumed to affect all races where both males and females are affected equally.

However, hereditary angioedema usually occur earlier in the 20s, while acquired angioedema commonly occurs after the 40s.

Progression

Angioedema is a type I hypersensitivity reaction. Type I hypersensitivity is characterized by Ig E mediated reaction. Ig E is a specific type of antibody that helps to fight infection, but also responsible for this type of allergic response.

There are certain drugs that are associated with angioedema:

Angiotensin-converting enzyme (ACE) inhibitors: to control high blood pressure

Nonsteroidal anti-inflammatory drugs (NSAIDs): commonly used as pain-killer

Radiocontrast agents: this are used in CT scans

Opiates: this include morphine, oxycodone and generally used as strong pain-killers

Aspirin: commonly used as pain relief

There are other common antigens causing angioedema:

insect stings

food such as fish, nuts, eggs, milk, chocolate, etc

after infection

animal protein

Angioedema usually progresses from minutes to hours, as typically occurs in type I hypersensitivity.

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