Persistent abnormal dilatation of the bronchi owing to localized and irreversible destruction and widening of the large airways.

Tracheal diverticula are blind-ended outpouchings arising from the trachea. They are usually an incidental finding. Occasionally they can mimic pneumomediastinum. Tracheal diverticula are either congenital or acquired, in the latter case the most common causes are prolonged increased intraluminal pressure, e.g. chronic cough, COPD, tracheomalacia, and iatrogenic (e.g. post-surgical).

An increased susceptibility to bronchopulmonary infections as manifested by a history of recurrent bronchopulmonary infections.