An optimal method for experimental provocation of polymorphic light eruption

Background: There is controversy about the best method to induce polymorphic light eruption (PLE) experimentally. Objectives: To review articles on PLE induction and design a UV radiation protocol that improves success rates with clinically relevant doses of environmentally relevant solar-simulated radiation (SSR). Design and Setting: All articles on the experimental provocation of PLE published since 1980 were reviewed. Photoprovocation of lesions was studied in 25 PLE patients. The 24-hour minimal erythemal dose (MED) of SSR was determined. Thereafter, six 4 X 4-cm adjacent sites on previously affected and previously unaffected skin were exposed to 0.25, 0.5, 0.75, 1.0, 1.25, 1.5 MED of SSR for 3 to 4 consecutive days. The study period was autumn to spring in London, England (510 north latitude). Main Outcome Measures: Relationship between PLE induction and biological and physical exposure parameters. Conclusions: The review shows that fractionated erythemally effective UV-A exposures were more successful than single-sunburning UV-B doses. Photoprovocation of PLE was successful in 68% of patients after 2 to 3 SSR exposures that were not necessarily erythemal. There was no difference in success rate between previously affected and previously unaffected skin. Our data indicate that PLE is more likely to be induced when the natural causes of the disease are simulated.