A 2-YEAR-OLD BOY presented to the emergency room with a 1-day history of a diffuse, mildly pruritic rash and swelling of his knees, ankles, and feet following treatment of acute otitis media with amoxicillin for the previous 8 days. He was mildly febrile and consolable, but he was refusing to walk. His medical history was unremarkable.
Physical examination revealed erythematous annular wheals on his chest, face, back, and extremities. Lymphadenopathy and mucous membrane involvement were not present. A complete blood count (CBC) with differential, inflammatory marker tests, and a comprehensive metabolic panel were ordered. Given the joint swelling and rash, the patient was admitted for observation.
During his second day in the hospital, his skin lesions enlarged and several formed dusky blue centers (FIGURE 1A). He also developed swelling of his hands (FIGURE 1B).
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