Pathogenesis of Woronoff ring in psoriasis

Abstract

• As a result of ultraviolet light and coal tar therapy, a white ring (Woronoff) may develop in the normal skin adjacent to psoriatic plaques. Injection of prostaglandin E₂(PGE₂) 1 cm outside of Woronoff ring produced redness in the ring, demonstrating that vessels within the ring were not unresponsive to PGE₂. Whole skin homogenates from Woronoff ring contained an inhibitor of prostaglandin synthesis that was not found in uninvolved skin that was obtained from either psoriatics or normal controls. Prostaglandin E₂levels in the ring were one third of those in uninvolved skin from either psoriatics or normal controls. These findings suggest that the white ring that surrounds ultraviolet-light-treated psoriatic plaques is produced by a local inability to synthesize PGE₂in response to an ultraviolet light stimulus, resulting from the presence of an inhibitor of prostaglandin synthesis. (Arch Dermatol112:955-957, 1976)