A 10-year-old boy has 3 weeks of migratory polyarthritis involving knees, ankles, elbows, and wrists following a sore throat 4 weeks ago. Examination reveals a painless, rapidly changing macular rash with erythematous rings and central clearing on the trunk, and a soft diastolic murmur at the apex. What is the diagnosis?

• A Serum sickness
• B Poststreptococcal reactive arthritis
• C Kawasaki disease
• D Acute rheumatic fever ✓

Explanation

Migratory polyarthritis, erythema marginatum, and carditis are three major Jones criteria, and evidence of preceding streptococcal infection completes the diagnosis. Poststreptococcal reactive arthritis lacks carditis and erythema marginatum and responds poorly to aspirin. Kawasaki requires prolonged fever with mucocutaneous findings, and serum sickness follows drug or antiserum exposure with urticaria rather than erythema marginatum.

Reference: Nelson Textbook of Pediatrics, 21st ed.

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