A 35 year old smoker with shortness of breath.

A previously well 35 year old man who currently smoked cigarettes (40 pack years) was referred because of a history of dyspnoea on exertion that had gradually got worse during the two months before presentation and a cough that was initially productive but then dry. He regularly smoked crack cocaine and took cocaine intranasally. At presentation he had hypoxaemia (partial pressure of oxygen 57 mm Hg), with a respiratory rate of 20 breaths/min. Physical examination showed only bilateral fine inspiratory crackles at the middle and lower zones of the chest. Initial blood tests were unremarkable. He had no signs of collagen tissue disorder, his autoantibody profile was negative, and HIV screening was negative. Chest radiography showed a bilateral reticular pattern at the middle and lower zones and bilateral infiltrates in the lower zones of the lung. Pulmonary function testing showed a restrictive pattern (total lung capacity 49%, forced expiratory volume in one second 48%, forced vital capacity 47%, diffusing capacity of the lung for carbon monoxide 36%). A 12 lead resting electrocardiogram showed sinus rhythm and an echocardiogram showed no abnormalities and no indirect evidence of pulmonary hypertension. Baseline saturation was 96% with a heart rate of 100 beats/min. During the six minute walking distance test he desaturated to 83% after three minutes and having completed 110 m. He underwent high resolution computed tomography of the chest (figs 1 and 2⇓ ⇓). Fig 1 High resolution computed tomography of the chest: upper lung zones Fig 2 High resolution computed tomography of the chest: lower lung zones