Pathogenesis of Woronoff ring in psoriasis

Area of Science:

• Dermatology
• Biochemistry
• Photobiology

Background:

• Psoriatic plaques treated with ultraviolet light or coal tar can develop a surrounding white ring, known as the Woronoff ring.
• The physiological basis for the formation of this specific skin reaction remains incompletely understood.
• Previous observations suggest altered vascular or cellular responses in the affected skin area.

Purpose of the Study:

• To investigate the role of prostaglandin E2 (PGE2) in the formation of the Woronoff ring.
• To identify potential biochemical factors within the Woronoff ring that may explain its altered physiology.
• To determine the vascular responsiveness of the Woronoff ring to exogenous PGE2.

Main Methods:

• Injection of prostaglandin E2 (PGE2) into the skin outside the Woronoff ring to assess vascular response.
• Analysis of whole skin homogenates from the Woronoff ring and uninvolved skin (psoriatic and normal controls) for prostaglandin synthesis inhibitors.
• Quantification of PGE2 levels in skin homogenates from the Woronoff ring compared to uninvolved skin.

Main Results:

• Injection of PGE2 induced redness within the Woronoff ring, indicating vascular responsiveness.
• Skin homogenates from the Woronoff ring contained an inhibitor of prostaglandin synthesis, absent in uninvolved skin.
• PGE2 levels were significantly lower (one-third) in the Woronoff ring compared to uninvolved skin.

Conclusions:

• The Woronoff ring is likely formed due to a localized inability to synthesize PGE2 following ultraviolet light stimulation.
• This impaired PGE2 synthesis is attributed to the presence of a prostaglandin synthesis inhibitor within the Woronoff ring.
• These findings elucidate a biochemical mechanism contributing to the characteristic skin changes observed in treated psoriasis.