Urticarial vasculitis.

The vasculitides are a heterogeneous group of disorders characterized by inflammation and necrosis of blood vessels. They have been classified into several major groups on the basis of the size and type of vessels affected and the type of inflammation. Urticarial vasculitis is a recently recognized but relatively common presentation of cutaneous necrotizing vasculitis. This article discusses its clinical, pathologic, and immunologic features, its association with other disease states, and its differentiation from nonvasculitic urticaria.