35 - Urticaria and Angioedema

Abstract

Acute urticaria is a common condition that affects up to 20% of the population and is generally self-limited. Factors associated with acute urticaria may be food or drug allergy in a minority of cases. In contrast, chronic urticaria is less common and afflicts approximately 1% of the population; in the vast majority of cases, skin lesions occur without an identifiable external trigger and are termed chronic spontaneous urticaria. Lesion pathology reveals mast cell degranulation and the infiltration by blood leukocytes. Several theories exist to explain disease pathogenesis, including the possibility of an autoimmune process or abnormal activation of skin mast cells. One-fifth of chronic urticaria patients describe a reproducible trigger for their skin lesions and are therefore termed chronic inducible urticaria (CIndU). This entity is further subdivided into those with a clear physical stimulus, termed physical urticaria. The evaluation of patients involves a detailed history, physical examination, and a limited panel of blood tests to exclude other systemic diseases. Therapy is aimed at the elimination of trigger factors, followed by symptomatic treatment with nonsedating antihistamines in a step-wise fashion. In patients in whom antihistamines are ineffective, or in those who have been dependent on oral corticosteroids for relief, the use of a biologic, omalizumab, is recommended. Several alternative immunomodulators can also be tried in refractory cases, with careful monitoring for toxicity. Most cases of chronic urticaria will resolve over the course of 2 to 3 years, with a longer duration for those with inducible urticaria.