A 3-year-old boy presents to his pediatrician for follow-up. He was seen two days prior with a 4-day history of fever ranging from 102°F (38.9°C) to 104°F (40°C), anorexia, and irritability. He is fully vaccinated and has not traveled outside Houston. His examination at that time was remarkable for bilateral conjunctivitis without discharge, and erythema of the lips, tongue, and pharynx. A rapid strep test was negative. A clean-catch urinalysis showed 2+ leukocytes but no other abnormalities. Because he had no other localizing symptoms, he was started on an oral cephalosporin for presumptive urinary tract infection pending urine culture results. Today he returns with persistent fever and irritability and does not want to walk; his mother attributes it to swelling of his feet. The physical findings noted previously are still present, but now he also has a maculopapular rash over his torso, nonpitting edema of the hands and feet, and a 1.7-cm non erythematous, non suppurative right anterior cervical lymph node. The urine culture and a throat culture from the previous visit show no growth. A complete blood cell count (CBC) shows a white blood cell count of 20,000/mm3, hemoglobin 10 g/dL, and platelets of 470,000/mm3. An erythrocyte sedimentation rate (ESR) measures 67 mm/h.
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