title: Repeated exposure to blue light does not improve psoriasis.
abstract: BACKGROUND
  Increased endogenous levels of protoporphyrin IX (PpIX) have been reported in the skin of patients with psoriasis. Activation of PpIX with blue light after exogenous topical application of its precursor, aminolevulinic acid, can improve psoriasis. Light activation of endogenous PpIX for the treatment of psoriasis has never been studied.
  
  
  OBJECTIVE
  The purpose of this study was to determine the efficacy of multiple exposures to blue light in patients with plaque psoriasis.
  
  
  METHODS
  A total of 17 patients with plaque psoriasis presenting increased endogenous level of PpIX were enrolled. Of the 2 identified plaques on each patient, 1 was exposed to 10 J/cm(2) of blue light from a fluorescent panel 3 times per week for 4 consecutive weeks. Plaque severity was assessed in a blinded fashion. PpIX levels were measured with in vivo fluorescence spectroscopy weekly.
  
  
  RESULTS
  A single exposure to blue light induced almost complete photobleaching of PpIX. There was no significant difference between the mean psoriasis severity score of the plaques before and after 12 exposures to blue light.
  
  
  CONCLUSIONS
  Repeated exposure to blue light did not improve psoriasis.
authors.affiliation: Division of Dermatology, University of Montreal Hospital Centre, Quebec, Canada.
authors.forename: Catherine
authors.initials: C
authors.lastname: Maari
authors.forename: Gilles
authors.initials: G
authors.lastname: Viau
authors.forename: Robert
authors.initials: R
authors.lastname: Bissonnette
mesh_terms: D000328:Adult; D000368:Aged; D006801:Humans; D008875:Middle Aged; D011524:Protoporphyrins / Q000032:analysis*; D011565:Psoriasis / Q000378:metabolism / Q000628:therapy*; D012867:Skin / Q000737:chemistry*
chemical_list: D011524:Protoporphyrins; C028025:protoporphyrin IX