Chronic Urticaria and Angioedema: Masqueraders and Misdiagnoses

Chronic urticaria is a common condition presenting with intensely pruritic wheals. Although individual lesions resolve within 24 hours, by definition, chronic urticaria lasts for a duration of at least 6 weeks. Both spontaneous and inducible forms exist. In the spontaneous variant, chronic urticaria occurs in the absence of clearly identifiable triggers. In chronic inducible urticaria, specific triggers may include dermatographism, cholinergic (heat), cold, exercise, delayed pressure, and solar. Extensive laboratory evaluation for chronic spontaneous urticaria is not required unless indicated by clinical history or physical examination. Angioedema describes sudden onset of localized edema involving the deep layers of the skin and submucosal tissues. It can be seen in isolation or in conjunction with chronic urticaria. Angioedema typically resolves slower than wheals, taking up to 72 hours or longer. Histamine- and bradykinin-mediated forms exist. Both chronic urticaria and angioedema have many mimics, and a broad range of differential diagnoses should be considered. Importantly, an incorrect diagnosis may have significant implications for the additional investigation, treatment, and prognosis of the affected patient. The aim of this article is to discuss the characteristics of chronic urticaria and angioedema, and an approach to the investigation and diagnosis of their mimics.