Urticaria, Angioedema, and Hereditary Angioedema
What is Urticaria
The earliest texts called urticaria and angioedema "a vexing problem". Little has changed since that assessment. Today's clinician is still faced with a common syndrome that affects 20% of the population at some time in their lives, but there is no cohesive understanding of the many clinical mechanisms, presentations, or clinical management of the urticarias. For the clinician, this requires a broad knowledge of the many clinical forms of urticaria and an even more extensive familiarity with the creative ways that medications and treatment can be applied. Modern concepts of allergen-induced cellular inflammation, late-phase cutaneous responses, adhesion molecules, cytokines, and inflammatory autocoids, are leading to a better understanding of pathogenesis and treatment. Meanwhile, clinicians should formulate a rational approach to the care of patients with these conditions.
Symptom of Urticaria and Angioedema
Urticarial lesions can have diverse appearances. Generally they consist of raised, erythematous skin lesions that are markedly pruritic, tend to be evanescent in any one location, are usually worsened by scratching, and always blanch with pressure. Individual lesions typically resolve within 24 hours and leave no residual skin changes. This description does not cover all forms of urticaria, but it includes the features necessary for diagnosis in most clinical situations. Angioedema is frequently associated with urticaria, but the two may occur independently. Angioedema is similar to urticaria, except that it occurs in deeper tissues and is often asymmetric. Because there are fewer mast cells and sensory nerve endings in these deeper tissues, pruritus is less common with angioedema, which more typically involves a tingling or burning sensation. Although urticaria may occur on any area of the body, angioedema most often affects the perioral region, periorbital regions, tongue, genitalia, and extremities. In this review, angioedema and urticaria are discussed jointly except where specified.
Evaluation of Acute and Chronic Urticaria
Acute urticaria is arbitrarily defined as persisting for less than 6 weeks, whereas chronic urticaria refers to episodes lasting more than 6 to 8 weeks. When considering chronic urticaria, an etiologic agent or precipitating cause such as a physical urticaria is established in up to 30% of patients who are thoroughly evaluated
Various forms of chronic urticaria have now been associated with eosinophil granule proteins presumed to be capable of causing prolonged inflammation of the skin.