Persistent polymorphous light eruption after ultraviolet A1 phototherapy.

Polymorphous light eruption (PMLE) is the most common photodermatosis and is characterized by the development of a pruritic skin eruption within a few hours to days after sun or artificial light exposure. The eruption usually takes up to two weeks to resolve in the absence of further ultraviolet radiation. PMLE has been reported as a side effect of ultraviolet A1 (UVA1) therapy but characteristics of the eruption, especially the duration until resolution after treatment, has not been described. A 37-year-old female developed an unusually persistent PMLE that lasted for 5 weeks after completion of UVA1 phototherapy.