A 20-MONTH-OLD infant had a 4-week history of bilaterally bulging neck masses that were apparent while crying. The masses were initially noted after an upper respiratory infection, and they became progressively more prominent. The infant had several episodes of difficulty swallowing, mild hoarseness, and occasional perioral cyanosis during a 5-day hospitalization to evaluate the neck masses. The infant's medical history was notable for respiratory syncytial virus bronchiolitis at age 6 months and several episodes of otitis media. There was no history of trauma or surgery.