Frequency of occurrence of polymorphic light eruption in patients treated with photohardening and patients treated with phototherapy for other diseases

BACKGROUND: Medical phototherapy can lead to the manifestation of polymorphic light eruption (PLE), though little is known about the frequency of such events. AIMS: The aim of this Austrian single center study was to retrospectively investigate over a 4‐year time period the frequency of PLE in patients prone to the condition and patients with other diseases under phototherapy (mainly narrow‐band and broad‐band UVB). MATERIALS AND METHODS: The data for analysis were obtained from the electronic health and patient record database and patient files of the Photodermatology Unit, Department of Dermatology, Medical University of Graz, Austria. RESULTS: PLE occurred in 24.3% (18/74) of PLE patients but only 0.7% (3/421) of psoriasis patients under phototherapy (chi‐square; P < 0.0001). PLE also occurred in 1.2% (3/257) of patients with atopic eczema, 0.8% (1/118) with prurigo, 3.5% (4/115, P = 0.0206) with parapsoriasis en plaques/mycosis fungoides, 7.4% (2/27, P = 0.0013) with granuloma anulare, 14.3% (1/7, P = 0.0002) with scleroderma, and 16.7% (1/6, P < 0.0001 vs. psoriasis) with pityriasis lichenoides chronica or pityriasis lichenoides eruptiva et varioliformis acuta. DISCUSSION AND CONCLUSION: These results are helpful for treatment allocation and risk estimation of PLE occurrence with regard to obtaining informed consent not only from PLE‐prone patients but also from patients with other skin disorders commonly treated by phototherapy.