Urticarial vasculitis in an infant.

Urticarial vasculitis (UV), a subtype of leukocytoclastic vasculitis, is a small vessel necrotizing vasculitis characterized by urticarial lesions and decreased serum complement. Primarily a disease of adult women, this immune complex disorder is seldom reported in children. Pathologic examination of skin lesions in patients with UV reveals leukocytoclastic vasculitis. UV is a frequent finding, particularly involving early components of the classical complement cascade C1q and C2 to C4. We report a 9-month-old male infant who presented with chronic urticaria of 7 months' duration that was unresponsive to conventional therapies for urticaria. His lesions appeared as erythematous wheals followed by the development of purpuric papules and resolving with ecchymoses and postinflammatory hyperpigmentation. Laboratory studies and skin biopsy results were consistent with UV.