002 Multiple exposures to blue light does not improve psoriasis in patients with elevated endogenous levels of protoporphyrin IX

Abstract

Endogenous levels of protoporphyrin IX (PpIX) are known to be elevated in psoriatic plaques. Activation of PpIX by visible light after topical application of aminolevulinic acid has been shown to improve psoriasis. This study was designed to determine whether multiple exposures to blue light alone could improve psoriasis in patients exhibiting elevated endogenous PpIX levels. Patients and methods: Seventeen patients with at least two psoriatic plaques of 4 × 4 cm exhibiting elevated endogenous PpIX levels (as detected by in vivo fluorescence spectroscopy) were included in the study. Patients were required to discontinue all topical therapies for at least 2 weeks and systemic therapy for at least 8 weeks before treatment. One of the two plaques on each patient was exposed to 10 J/cm2 Of blue light from a fluorescence panel three times per week for 4 consecutive weeks. The other plaque was used as a non-exposed control. Blinded clinical evaluations were performed at baseline and every week during the 4-week treatment period as well as at 1 and 3 weeks after the last exposure. Psoriasis severity was assessed by evaluating on a scale of 0–4 the presence of erythema, induration, and desquamation. PpIX levels were measured before and after light exposure by in vivo fluorescence spectroscopy at week 1 and 4. Results: All patients completed the study without presenting treatment related side-effects. In vivo fluorescence spectroscopy demonstrated an almost complete photobleaching of PpIX in exposed plaques immediately after light exposure (P = 0.005). There was no significant difference between the mean psoriasis severity score of the exposed or control plaques before and after 12 exposures to blue light. Conclusion: Under the current conditions multiple exposures to blue light did not improve psoriasis.