Differential diagnosis of chronic urticaria.

Objectives: To review diseases that can present with cutaneous signs and symptoms that mimic those observed in chronic urticaria and to discuss the workup necessary to distinguish these diseases from chronic urticaria.

Data Sources: We performed a PubMed search using the following keywords: urticaria, cryopyrin, Sweet syndrome, subacute cutaneous lupus, urticarial vasculitis, urticaria pigmentosa, angioedema, fixed drug eruption, bullous pemphigoid, and reticular erythematous mucinosis. Appropriate chapters in general dermatology textbooks were also reviewed.

Study Selection: Articles that related to disease states, which present with persistent urticarial lesions, were catalogued for use in this review.

Results: Besides acute, chronic, and physical urticarias, there are 2 categories of diseases that have urticarial lesions. The first group includes those in which the skin lesions are almost indistinguishable from those seen in patients with chronic idiopathic urticaria. Thus, the diagnosis relies on a careful history and physical examination, and in some cases laboratory studies are required. The second group are ones that have skin lesions that at one point in their development have an urticaria-like appearance or on rare occasion may have such lesions. These latter diseases are numerous, and we have tried to highlight the ones that most mimic chronic idiopathic urticaria or are more common.

Conclusions: A working knowledge of the diseases that can present with urticarial lesions is essential to accurately diagnose and effectively treat these symptomatic and sometimes serious conditions.