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Polymorphous light eruption. A case report and consideration of the hardening mechanism
M Watanabe1, H Yamanouchi, F Ogawa
1Department of Dermatology, Nagasaki University School of Medicine, Nagasaki, Japan.
Background:
Polymorphous light eruption (PLE) is a common form of photodermatosis. The pathogenesis of the disease and the mechanism of the hardening phenomenon, however, have not been clarified.
Observation:
We report a 62-year-old Japanese woman with PLE. Provocation and hardening induction testing revealed that hardening was induced at the sites irradiated by a sufficient dose of UV for reproduction of the lesion. Topical steroid could prevent a positive reaction but not the hardening induction. The expression of adhesion molecules and CD1a was decreased at the hardening site.
Conclusion:
From these results, the hardening phenomenon in our case might be due to immunosuppression by UV exposure supported by the down-regulation of cell adhesion molecule expression and partially due to the depletion of endogenous antigens which cause a delayed-type hypersensitivity reaction.