- Etiology: intrinsic airway lumen narrowing due to dysplastic bronchial cartilage or extrinsic airway lumen narrowing leading to congenital ball valve effect and hyperinflated lobe
- CXR: single large lesion with retention of fluid at birth and air trapping later
- Imaging: Usually unilateral and involves one lobe, usually affects upper lobes (left upper lobe > right middle lobe > right upper lobe > lower lobes), has normal blood supply from pulmonary artery
- Clinical: symptomatic during infancy