LAUSR

A 45-year-old white woman presented for photorejuvenation of her upper back and arms. Two 1927-nm nonablative fractional laser treatments were performed to her upper back, spaced 8 weeks apart. Over a similar period, she underwent 3 treatments to her bilateral arms, spaced 4 to 6weeks apart. The laser settings were as follows: energy of 10 mJ, treatment Level 4, and 4 to 6 passes. A slightly pruritic, papular rash appeared on the patient’s arms 7 to 10 days after the last arm treatment. The pink papules and pseudovesicles spread to the patient’s back, most without apparent central umbilication (Figure 1A,B). The differential diagnosis included folliculitis, candidiasis, and polymorphous light eruption, among others. A shave biopsy was performed and confirmed the diagnosis of MC with the pathognomonic Henderson–Patterson bodies (Figure 2). The lesions resolved with cryotherapy and topical imiquimod, with no residual scarring. The patient did later admit to brief exposure to children infected with MC. Of note, she was otherwise healthy and was not taking any immunosuppressive agents.