A 6-year-old child presented to the emergency department with left upper-quadrant abdominal tenderness and a persistent fever. He had a white blood cell count of 30,000/μL, and a computed tomographic image of the abdomen showed splenic fluid (image A). A splenic drainage tube was placed and collected aseptic fluid with neutrophilic infiltration, indicating an aseptic splenic abscess. After tube removal, a tender, raised, and ulcerated skin lesion appeared over the drain site with violaceous rolled borders. Another kissing lesion appeared on the medial left brachium at the site of the intravenous line (image B). Tissue samples revealed aseptic intraepithelial neutrophilic infiltration. Based on the persistent fever, elevated white blood cell count, and pyoderma gangrenosum, Sweet syndrome was diagnosed. The patient was treated with systemic cyclosporine, prednisone, and topical FK-506 and made an unremarkable recovery. 

Sweet syndrome, also referred to as acute febrile neutrophilic dermatosis, is a hypersensitivity reaction with symptoms and laboratory findings of fever; neutrophilia; leukocytosis; an abrupt onset of tender, erythematous, and violaceous inflammatory papules, nodules, and plaques; and high inflammatory markers.¹ Diagnostic criteria are outlined by von den Driesch,² and treatment consists of systemic corticosteroids or potassium iodide.