Urticaria is composed of wheals (transient edematous papules and plaques, usually pruritic and due to edema of the papillary body). Angioedema is a larger edematous area that involves the dermis and subcutaneous tissue. Urticaria and/or angioedema may be acute recurrent or chronic recurrent. There are some syndromes with angioedema in which urticarial wheals are rarely present (e.g., hereditary angioedema).
Causes of Urticaria and Angioedema
Lesions in acute IgE-mediated urticaria result from antigen-induced release of biologically active molecules from mast cells or basophilic leukocytes sensitized with specific IgE antibodies (type I anaphylactic Hypersensitivity). Mediators released increase venular permeability and modulate the release of biologically active molecules from other cell types.
In complement-mediated urticaria, complement is activated by immune complexes; this results in the release of anaphylatoxins, which, in turn, induce mast cell degranulation.
In chronic idiopathic urticaria, histamine derived from mast cells in the skin is considered the major mediator. Other mediators, including eicosanoids and neuropeptides, also may play a part in producing the lesions, but direct measurement of these mediators has not been reported. Intolerance to salicylates and food preservatives and additives, such as benzoic acid and sodium benzoate, as well as several azo dyes, including tartrazine and sunset yellow; is presumably mediated by abnormalities of the arachidonic acid pathway.
In 40% of patients with chronic urticaria an anti-FceRI autoantibody has been identified and a positive correlation between histaminereleasing activity and disease activity has been demonstrated. Clinically, patients with these autoantibodies are indistinguishable from those without them. These autoantibodies may explain why plasmapheresis, intravenous immunoglobulins, and cyclosporine induce remission of disease activity in these patients. The concept that some chronic urticarias are a manifestation of autoimmune mast cell disease is also supported by the association of chronic urticaria with autoimmune thyroid disease (14%).
In hereditary angioedema, decreased or dysfunctional CI-esterase inhibitor leads to increased kinin formation. The angioedemaurticaria-eosinophilia syndrome may result from the eosinophilia that is markedly elevated in the skin. In this syndrome, the eosinophilia increases and decreases with the angioedema and urticaria; major basic protein is distributed after its release from the eosinophil between the collagen bundles, and mast cells in the dermis show degranulation.
Symptoms of Urticaria and Angioedema
- Sudden and severe swelling of your face, arms, legs, hands, feet, genitalia, digestive tract and airway
- Abdominal cramping as a result of digestive tract swelling
- Difficulty or obstructed breathing due to swelling of your airway
Diagnosis
A detailed history (previous diseases, drugs, foods, parasites, physical exertion, solar exposure) is of utmost importance. Most difficult to evaluate is chronic urticaria. A practical approach to the diagnosis of chronic urticaria. A careful history of medications including aspirin and nonsteroidal anti-inflammatory drugs should be obtained. If physical urticaria is suspected, appropriate challenge testing should be performed. Cholinergic urticaria can best be diagnosed by exercise to sweating and intracutaneous injection of acetylcholine or mecholyl, which will produce micropapular whealing. Solar urticaria is verified by testing with UVB, UVA, and visible light. Cold urticaria is verified by a wheal response to the application to the skin of an ice cube or a test tube containing ice water. If urticarial wheals do not disappear in 24 h or less, urticarial vasculitis should be suspected and a biopsy done. The angioedema-urticaria-eosinophilia syndrome has high fever, high leukocytosis (mostly eosinophils), a striking increase in body weight due to retention of water, and a cyclic pattern that may occur and recur over a period of years. Hereditary angioedema has a positive family history and is characterized by angioedema of the face and extremities as the result of trauma, abdominal pain, and decreased levels of C4 and C1-esterase inhibitor or a dysfunctional inhibitor.
Treatment
Antihistamines H1 blockers, e.g., hydroxyzine, terfenadine; or loratadine, cetirizine, fexofenadine. 180 mg/d of fexofenadine or 10 to 20 mg/d of loratadine usually controls most cases of chronic urticaria, but cessation of therapy usually results in a recurrence; if they fail, H1 and H2 blockers (cimetidine) and/or mast cell-stabilizing agents (ketotifen). Doxepin, a tricyclic antidepressant with marked H1 antihistaminic activity, is valuable when severe urticaria is associated with anxiety and depression.
Prednisone Indicated for angioedemaurticaria-eosinophilia syndrome.
Danazol Long-term therapy for hereditary angioedema; whole fresh plasma or C1-esterase inhibitor in the acute attack.
Prevention
Try to prevent attacks by elimination of etiologic chemicals or drugs: aspirin and food additives, especially in chronic recurrent urticaria-rarely successful.
References