Persistent diffuse pulmonary interstitial emphysema mimicking pulmonary emphysema.

A 69-year-old male non-smoker with a history of atopic asthma presented with symptoms suggestive of chronic obstructive pulmonary disease and this appeared to be corroborated by lung function testing and a chest radiograph. However, a chest CT showed no evidence of pulmonary emphysema and instead demonstrated free air along the bronchovascular sheaths indicative of pulmonary interstistial emphysema, possibly caused by repeated prior exacerbations of asthma. His lung function tests and symptoms improved within months of being treated for his airways disease but the CT findings were unchanged after 2 years.