An 11-year-old girl presented with acutely itching, target-like bullous lesions on the back of both hands. The blisters had arisen 3 weeks earlier following ultraviolet light (UV) exposure. Inspection disclosed accompanying residual herpes simplex lesions on the upper lip, and we suspected erythema multiforme. Histological examination showed superficial and deep lymphocytic infiltrates, spongiosis, and a normal stratum corneum, findings compatible with polymorphous light eruption. The absence of necrotic keratinocytes and the concentration of the itchy skin lesions in UV-exposed areas also speak against the diagnosis “erythema multiforme”. Further questioning revealed that the skin rash and the herpes simplex infection did not begin at the same time. We initiated topical treatment with fusidic acid and betamethasone. The patient was advised to avoid direct sunlight and use protective sunscreen lotion. Prophylactic phototherapy was planned. Polymorphous light eruption is the most frequently occurring form of immune-mediated photodermatitis. It arises from a few hours to a few days after light exposure and is viewed as a delayed hypersensitivity reaction to newly UV-induced antigen(s).
Translated from the original German by David Roseveare
Cite this as: Miguel D, Lindhaus C: Polymorphous light eruption mimicking erythema multiforme.
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Footnotes
Conflict of interest statement:
The authors declare that no conflict of interest exists.