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Author: Vanessa Ngan, Staff Writer, 2006.
Angioedema is a skin reaction similar to hives or urticaria. It is most often characterised by an abrupt and short-lived swelling of the skin and mucous membranes. All parts of the body may be affected but swelling most often occurs around the eyes and lips. In severe cases the internal lining of the upper respiratory tract and intestines may also be affected.
Angioedema and urticaria are very similar in many ways and can co-exist and overlap. Urticaria occurs more commonly and is less severe than angioedema as it only affects the skin layers whereas angioedema affects the tissues beneath the skin (subcutaneous tissue). The main differences between urticaria and angioedema are shown in the following table.
|Tissues involved||Subcutaneous and submucosal surfaces (beneath the dermis)||Epidermis (outer layer of skin) and dermis (inner layer of skin)|
|Organs affected||Skin and mucosa, particularly the eyelids and lips||Skin only|
|Duration||Transitory (usually lasts between 24-48 hours)||Transitory (usually lasts < 24 hours)|
|Physical signs||Red or skin coloured swellings occurring below the surface of the skin||Red patches and weals on the surface of skin|
|Symptoms||May or may not be itchy. Often accompanied by pain and tenderness.||Usually associated with an itch. Pain and tenderness uncommon.|
The causes of angioedema depend on the type of angioedema a patient has. Angioedema can be classified into at least four types, acute allergic angioedema, non-allergic drug reactions, idiopathic angioedema, hereditary angioedema (HAE) and acquired C1 inhibitor deficiency.
|Acute allergic angioedema
(almost always occurs with urticaria within 1-2 hours of exposure to the allergen)
|Non-allergic drug reaction
(onset may be days to months after first taking the medication)
(frequently chronic and relapsing and usually occurs with urticaria)
(very rare autosomal dominant inherited disease)
|Acquired C1 inhibitor deficiency||
Whatever the cause of angioedema, the actual mechanism behind the swelling is the same in all cases. Small blood vessels in the subcutaneous and/or submucosal tissues leak watery liquid through their walls and cause swelling. This same mechanism occurs in urticaria but just closer to the skin surface.
Symptoms and signs of angioedema may vary slightly between the different types of angioedema but in general some or all of the following occur.
Some features specific to the different types of angioedema are listed below.
|Angioedema type||Clinical features|
|Non-allergic drug reaction||
A detailed medical history is invaluable in diagnosing angioedema.
Skin prick testing may be performed to try and identify any allergens. If hereditary angioedema is suspected, blood tests to check for levels and function of specific complement blood proteins may be done.
Treatment of angioedema depends on the severity of the condition. In cases where the respiratory tract is involved the first priority is to secure the airway. Patients may need emergency hospital care and require intubation (placement of a tube in the throat to keep the airway open).
Patients with mild acute angioedema can usually be treated the same way as those with an allergic reaction (see urticaria). In many cases the swelling is self-limiting and resolves spontaneously after a few hours or days. In more severe cases where there is persistent swelling, itchiness or pain the following medications may be used.
Chronic angioedema with chronic autoimmune or chronic idiopathic urticaria is often difficult to treat and response to medication variable. The following treatment steps are recommended. Each step is added to the previous one if inadequate response is obtained.
|Step 1:||non-sedating antihistamines, e.g. cetirizine|
|Step 2:||sedating antihistamines, e.g. diphenhydramine|
|Step 3:||a) oral corticosteroids, e.g. prednisone
b) immunosuppressants e.g. ciclosporin or methotrexate
Omalizumab, an anti-IgE monoclonal antibody, has been reported to be effective in some refractory cases of angioedema.
The goal of treatment for chronic angioedema is to reduce itch, swelling, tenderness and pain to a tolerable level to maintain function (e.g. work, school, sleep).
Acute episodes of hereditary angioedema do not respond to adrenaline, antihistamine and corticosteroids. Fortunately most acute episodes of Type I and II hereditary angioedema are non life-threatening.
The chance of an attack can be reduced with the following medications:
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