An infant with a hyperlucent chest mass: An unexpected diagnosis.

Introduction: We report an unusual finding of pneumatocele in an infant.

Case Report: A previously well four month old presented with worsening respiratory distress over 6 weeks. He had no antecedent signs or symptoms of respiratory infection. Chest radiograph demonstrated a lucent hemithorax concerning for tension pneumothorax. Urgent needle decompression was performed. Chest CT showed a persistent dominant macrocyst on the left. Thoracotomy revealed a large cystic lesion necessitating a left lower lobectomy. Histopathology was consistent with a pneumatocele. He remains clinically stable at 16 months postoperatively.

Discussion: Pneumatocele is a rare cause of cystic lung disease presenting in infancy. The young age at onset, prolonged symptoms without preceding infection, and tension physiology in our patient are unique.