Background: Polymorphous light eruption (PLE) is an idiopathic eruption induced by ultraviolet (UV) radiation (UVR). Objective: Evaluation of the clinical aspects, diagnostic criteria of PLE in a major Swiss referral center. Methods: 25 patients with PLE were tested with a standardized protocol for the assessment of photodermatoses. Results: 25 patients (22 women vs. 3 men) were identified. Papular and papular-vesicular eruptions were the most common clinical presentations. 6 of 25 patients had a reduced minimal erythema dose (MED) für UVA and 8 of 25 patients had a reduced MED for UVB. Photoprovocation was positive in 11 of 20 patients for UVA and 7 of 20 patients for UVB. Photohardening with narrow-band UVB was successful in 8 of 10 patients. Combined UVA/UVB therapy had a satisfactory effect in 10 of 15 patients. Narrow-band UVB therapy was still successful after ineffective UVA/UVB therapy. Conclusion: The MED was of no value for the diagnosis of PLE. The typical lesions were reproduced by UVA and UVB photoprovocation. We recommend photohardening with narrow-band UVB (311 nm).

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