A previously healthy, 10-year-old boy presented with 5 days of fever and malaise. He also complained of cough, shortness of breath, sore throat, and myalgias. Three days earlier, he developed the erythematous, annular, and polycyclic rash pictured (Figure). The lesions were blanching and coalesced in some areas; a subset of the lesions had dusky central zones. The rash waxed and waned and lesions appeared in different areas of the body at different times. When the rash was intense, he noticed periorbital and perioral edema. The erythematous macules faded, leaving no residual skin changes. There was some improvement with diphenhydramine treatment.
On physical examination, the child was afebrile. He had rales and rhonchi in the left lung base and mild tenderness to palpation diffusely over his large muscles. He had no hepatosplenomegaly or lymphadenopathy. He had no joint swelling or tenderness. He had a rash as shown.
Figure.
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