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Urticarial vasculitis is an ill-defined entity in which patients develop urticarial plaques that persist for more than 24 hours. Histologically, features of leukocytoclastic vasculitis are seen. To determine the earliest events in the pathogenesis of urticarial vasculitis, investigators biopsied exercise-induced urticarial vasculitic lesions from one patient four times over a 24-hour period.
Clinically, the lesions appeared 10 hours after the exercise challenge, became purpuric by 24 hours, and resolved within 72 hours. Initial biopsies taken before the exercise challenge revealed the presence of immune complexes within dermal blood vessel walls, a finding not seen in ordinary urticarial lesions. The earliest histologic changes after exercis…