title: Polymorphous light eruption. A case report and consideration of the hardening mechanism.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Dermatology, Nagasaki University School of Medicine, Nagasaki, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Watanabe
authors.forename: H
authors.initials: H
authors.lastname: Yamanouchi
authors.forename: F
authors.initials: F
authors.lastname: Ogawa
authors.forename: I
authors.initials: I
authors.lastname: Katayama
mesh_terms: D018949:Antigens, CD1 / Q000378:metabolism; D019040:E-Selectin / Q000378:metabolism; D005076:Exanthema / Q000209:etiology* / Q000276:immunology / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D008875:Middle Aged; D010328:Patch Tests; D010787:Photosensitivity Disorders / Q000209:etiology* / Q000276:immunology / Q000378:metabolism; D017319:Photosensitizing Agents / Q000276:immunology; D011836:Radiation Tolerance; D012871:Skin Diseases / Q000209:etiology* / Q000276:immunology / Q000378:metabolism; D013472:Sunlight / Q000009:adverse effects; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D018949:Antigens, CD1; D019040:E-Selectin; D017319:Photosensitizing Agents; D018799:Intercellular Adhesion Molecule-1