Infectious urticaria with purpura: a mild subtype of urticarial vasculitis?

Urticaria is characterized by transient wheals. We report here five cases with long-lasting urticarial lesions persisting for more than 24 hours. Each lesion left purpura after fading. There was no systemic involvement. C-reactive protein and serum levels of complement were elevated or normal. Histologically, marked infiltration by eosinophils and neutrophils with karyorrhexis in the perivascular and intercollagenous spaces was observed, but there was no evidence of vasculitis (venulitis). Skin symptoms were resistant to systemic corticosteroids. In contrast, treatment of underlying bacterial infections resulted in marked improvement of skin lesions. E-selectin, VCAM-1 and ICAM-1 were expressed on endothelial cells. Marked deposition of C3a, C5a, neutrophil elastase and major basic protein in the dermis was observed. These urticarial lesions provoked by bacterial infections seem to lie on the continuum between urticaria and urticarial vasculitis.