Polymorphous light eruption: the properties of a UVA-induced PLME patient group.

Experimental induction of PLME lesions in 22 patients, using a pure, high-intensity UVA light source is reported. Fourteen patients had a reduced MED value for either UVB (11 patients) and/or UVA (7 patients). The UVA-SUN 2000 dose required to provoke a positive PLME reaction varied from 26 to 104 J/cm2. The small papular PMLE-type patients were shown to be more photosensitive and the UVA provocation doses required exceeded 50 J/cm2 in 20/22 patients. Lesional immunoglobulin deposition along the BMZ was seen in 3 patients while lesional BMZ complement deposits occurred in 9/15 patients, 2 of whom had similar findings in the dermal capillaries. Complement deposition occurred in non-irradiated control sites in 4 patients. The immunohistologic findings, for reasons given, fail to support the hypothesis of an immune cell-mediated response as the primary event in the pathogenesis of PMLE.