[The patient with polymorphous light dermatosis. Skin type, hardening and other light-associated markers]

From 1985 to 1989 we interviewed 312 patients suffering from polymorphous light eruption (PLE). The interviews were based on a questionnaire dealing with the various light-dependent factors that exacerbate the disease. Of 90 patients who were tested with artificial UV-A and UV-B irradiation sources, 60 reacted with typical PLE lesions: (a) 27 patients to UV-A alone, (b) 12 to UV-B alone, and (c) 21 to both UV-A and UV-B. Using UV-A provocation tests we were able to determine the anamnestic criteria indicating a possible UV-A induction of PLE, e.g. occurrence in the shade, no protection from window glass, no benefit from conventional sunscreens, and occurrence in solaria. The period from experimental irradiation to induction of skin lesions was shorter in skin types I and II than in skin type III and IV. Hardening phenomenon was reported by 37% of our patients. Of the UV-A-positive patients, 38% showed the first presentation of PLE lesions at the height of summer, as against 64% of the total number of patients questioned. Additional lesions at non-irradiated skin sites occurred in 25% of our patients, the frequency rising with increasing duration of the tendency to PLE.