Unilateral hypertranslucency of the left hemithorax due to aneurysm of the thoracic aorta

A 19 year old man presented with a six months history of dyspnoea on exertion. Chest radiographs, isotopic lung scans, and computed tomographic scans of the chest showed unilateral translucency of the left lung, absence of ventilation and perfusion in the same lung, and a 3.5 cm aneurysm of the descending thoracic aorta which compressed the left mainstem bronchus.