A 19 year old man presented with a six months history of dyspnoea on e
xertion. Chest radiographs, isotopic lung scans, and computed tomograp
hic 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 ma
instem bronchus.