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Woronoff's Ring

Woronoff's ring is a section of paler-than-normal (hypopigmented) skin which can sometimes be found surrounding a psoriasis plaque, especially those being treated with UV light and/or coal tar. From what I've found, there's no indication that these rings pose any problems, and they are transitory.

Medical speculation over the last 30-something years, for which there is some evidence, says that Woronoff's rings are due to a chemical being released from psoriasis plaques. The chemical may be a prostaglandin inhibitor, which would mean fewer capillary-dilating prostaglandins around a plaque, leading to skin with little blood in it. However, at least one study found decent blood flow in Woronoff's rings, calling that hypothesis into question.

So it would appear that nobody really knows why Woronoff's rings appear, and one group of researchers found that it was possible to induce Woronoff's rings around sites of skin trauma in people without psoriasis, so this phenomenon may not be unique to this disease.

General Information:

• Answers, AIIMS May 2002 (Question 189)
• Hypopigmented Skin Lesions
• Military Dermatology, Chapter 20 (page 5)
• Pediatric Database

German Information:

• Aus der Klinik für Dermatologie und Allergologie des St. Josef-Hospitals
• An Exam (Question 144)

Citations, Articles & Abstracts:

• "A human model system for the release of endogenous inhibitor(s) of prostaglandin biosynthesis." Simon et al, Prostaglandins 1977 Aug;14(2):363-9
• "Local variation in cutaneous and subcutaneous blood flow measured by CdTe(C1) minidetectors in normal and psoriatic skin." Klemp and Bojsen, The Journal of Investigative Dermatology 1986 Feb;86(2):109-14
• "Pathogenesis of Woronoff ring in psoriasis." Penneys et al, Archives of Dermatology 1976 Jul;112(7):955-7
• "Scientific Update - Psoriasis" Bhavsar and Shah, Gujarat Medical Journal News Bulletin 2002 Nov;49(1):6-8
• "Woronoff ring during anthralin therapy for psoriasis." Gupta et al, Archives of Dermatology 1986 Mar;122(3):248
• "The Woronoff ring in psoriasis." Varma and Finlay, British Journal of Dermatology 2003 Jan;148(1):170
• "The Woronoff ring of psoriasis: study of a patient." Koplon et al, International Journal of Dermatology 1971 Oct-Dec;10(4):233-6
• "[Woronoff rings in a mathematical model]" Groebe et al, Hautarzt 1990 Apr;41(4):226-8
• "The Woronoff zone surrounding the psoriatic plaque." van de Kerkhof, British Journal of Dermatology 1998 Jul;139(1):167-8

Footnotes Only:

• British Journal of Dermatology
• Crutchfield Dermatology - Bibliography
• Medline Repository
• YSI 5300A References-Pathology and Toxicology

Thanks to Screeee for introducing me to the term 'Woronoff's Ring'.