Polymorphic light eruption.

Polymorphic light eruption (PMLE) is the most common photodermatosis. It is typically characterized by nonscarring, pruritic, erythematous papules, plaques, or vesicles on sun-exposed skin that develop 30 minutes to several hours after sun exposure. The eruption may persist for a few hours to as long as 2 weeks. Females are affected two to three times more often than males. PMLE has been reported in all races, but tends to affect fair-skinned individuals with Fitzpatrick skin types I-IV most commonly. The pathogenesis of PMLE has been difficult to define, although it appears to be an immune-mediated delayed-type hypersensitivity reaction. Abnormalities of arachidonic acid metabolism and a possible correlation with lupus are other theories that are reviewed. Treatment options have been explored extensively. While "hardening" or desensitization of the skin through repeated irradiation seems to be the most effective, therapeutic options such as sun avoidance/sun protection, oral carotenoids, and antimalarials are also considered.