Congenital lung overinflation secondary to a unilateral obstructing mediastinal bronchogenic cyst

We present the case of a 39 week-gestational age female infant who, following an uncomplicated pregnancy developed progressively worsening respiratory distress. She was diagnosed with a mediastinal bronchogenic cyst which was intermittently occluding the left mainstem bronchus, leading to overinflation of the left lung, mediastinal shift with the heart in the right chest and a hypoplastic right lung. Despite luminal stenting, the left lung remained enlarged with the right lung hypoinflated. Interestingly, there was no physiologic consequences to the significant mediastinal shift. We hypothesize that the process began in utero where the bronchogenic cyst caused unilateral bronchial occlusion triggering left lung hyperplasia. The cyst was resected without complication and the patient suffered no further respiratory issues.