Urticarial plaques that last longer than 24 hours and burn or sting more than they itch characterize urticarial vasculitis. Histologically, urticarial vasculitis sits in a continuum lying between chronic urticaria and conventional cutaneous leukocytoclastic vasculitis. The infiltrates tend to be sparser than conventional LCV, but neutrophil dominant compared to chronic urticaria. The presence of slight nuclear debris and/or scattered
extravasated red blood cells is a histologic clue to urticarial vasculitis. Direct immunofluorescence examination reveals vascular deposition of
immunoreactants, mostly C3 or IgM,in .50% of all patients.Am J Dermatopathol Volume 28, Number 6, December 2006