Angioedema

Angioedema, with or without urticaria, is classified as allergic, hereditary, or idiopathic.

Allergic and idiopathic angioedema

Allergic angioedema (IgE mediated) and idiopathic, is caused by mast cell degranulation causing release of histamine, prostaglandins, leukotrienes and thromboxanes.

There may not be a preceding history of allergy or the patient may not be able to recall the exposure to the allergen.

More than 90% of patients have some combination of urticaria, erythema, pruritus, or angioedema. Airway compromise is caused by the resultant vasodilatation and associated oedema.

Immediate treatment is with an age-based dose of intramuscular adrenaline as per the algorithm below. Other beneficial treatments include oxygen, steroids, H1 and H2 blockers, IV fluids and consideration of intubation.

If adrenaline is required, the child must be admitted for observation due to the risk of re-occurrence after six hours. This is 6 hours after the symptoms have resolved and that this is due to the risks of biphasic anaphylaxis that occurs in up to 4.5% [26] of allergic reaction with and average time between reactions of 6-10 hours (Mean 8.13. [27]

On discharge, children should be referred to an allergy specialist; receive training on the use of an adrenaline auto-injector e.g. Epipen or Anapen and be discharged with two adrenaline auto-injectors, one of which should be kept at school.

Click the thumbnail to see the algorithm on anaphylaxis.

Learning bite

Adrenaline is the first pharmacological intervention with a child with anaphylaxis.

Heredetary angioedema

Hereditary angioedema (HAE) is an autosomal dominant disorder of C1 inhibitor. Oedema formation is related to the reduction or dysfunction of C1 inhibitor which results in the release of bradykinin and C2-kinin mediators. This enhances vascular permeability and leads to extra-vascular fluid shifts. [29]

Approximately 40% of people with HAE present with the first episode before the age of 5 years and 75% present before age 15 years. Attacks normally occur at a single site. The life time risk of laryngeal involvement during an attack is about 70%, although uncommon in  children. [30] Other presentations are subcutaneous angioedema and abdominal attacks.

Subcutaneous angioedema is circumscribed, non-puritic and non-erythematous swelling of the skin. Almost 100% of patients with HAE will experience this in their lifetime. 45% of attacks involve the limbs but can also develop on the face, neck, genitals and trunk. Skin oedema occurs in 50% of all attacks. Abdominal attacks mimic an acute abdomen with abdominal pain, vomiting, diarrhoea and even ileus. [31]

For severe HAE attacks i.e. facial, tongue, oropharyngeal swelling, dysphagia, voice alteration, or severe abdominal pains; administration of C1 inhibitor concentrate is the treatment of choice (table 1). Clinical improvement is seen within 15 to 60 minutes. A repeat dose may be required if symptoms are not relieved within an hour. [32] If C1 inhibitor concentrate is not available then fresh frozen plasma (10 ml/kg) or solvent detergent treated plasma (Octaplas) can be used. [33]

Table 1 Dose of C1 inhibitor concentrate

Weight	Dose
<50 kg	10 units per kilogram
50-100 kg	1000 units
>100 kg	1500 units

Learning bite

HAE does not respond to adrenaline.