Urticaria and angioedema: A clinical spectrum

Objective: The objective of this review is to give the reader a global insight into the spectrum of urticaria, focusing on differential diagnosis and pathogenic mechanisms. This review will define the role of the mast cell, explore a possible autoimmune basis for urticaria, and examine the purported role of food allergy in chronic urticaria. Last, the work-up and treatment of urticaria will be discussed in the context of the histologic diagnosis. Study Selection: The relevant past medical literature will be reviewed in the context of new and novel research into the mechanisms of chronic urticaria. Results: Urticaria can be classified histopathologically into the following three categories: (1) neutrophilic vasculitis, (2) polymorphous perivascular infiltrate, and (3) sparse perivascular lymphocytic infiltrate. Each of the above histologic patterns correlates with a distinct clinical entity and the work-up and treatment of urticaria will be related to each of the above histologic types. Conclusions: Urticaria and angioedema are frustrating problems for both physicians and their patients; however, the problem can best be approached by considering urticaria as a symptom that may be part of a larger clinical spectrum. The physical examination and medical history remain the two most important pieces of information. The allergist frequently overlooks the value of a skin biopsy as an aid in sorting out the pathophysiology of urticaria and the biopsy results may help to classify urticaria into subgroups which respond differently to treatment.