Introduction
Bronchial atresia is a rare condition, typically affecting the subsegmental bronchi1, and often noted on prenatal ultrasounds as a hyperexpanded fluid filled lung segment. The more proximal the atresia, the more severe and life-threatening the presentation. Only ten cases of mainstem bronchial atresia (MBA) have been reported to date, with universally poor outcomes2-6. Unlike peripheral bronchial atresia, MBA presents a unique challenge with expansion of the involved lung, mediastinal compression and contralateral shift, hydrops and fetal or infant death. This represents a form of unilateral Congenital High Airway Obstructive Syndrome (CHAOS), with laryngeal or tracheal atresia causing bilateral lung hyperexpansion and diaphragmatic eversion7.