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.