Traumatic pulmonary pseudocyst is a rare complication of blunt chest trauma that usually appears immediately in children or young adults and is characterized by a single or multiple pulmonary cystic lesions on chest radiography and has spontaneous resolution of the radiologic manifestations.
However, we experienced a case of a delayed complicated pulmonary pseudocyst in a 17-year-old boy following severe traumatic acute respiratory distress syndrome rescued by Veno-venous extracorporeal membrane oxygenation (ECMO). In this case, the pseudocyst appeared on the 12th day after trauma and transformed into an infected cyst. Veno-venous ECMO was successfully maintained for 20 days without anticoagulation.