A 29 year old unemployed woman who had never smoked was referred to the outpatient clinic with a 10 month history of non-productive cough, breathlessness, and chest tightness. Her exercise tolerance had reduced dramatically from breathlessness on exertion to symptoms at rest over six months. She had been treated for asthma in the community for six months before attendance, although inhalers had conferred little improvement in symptoms. She lived alone and had kept budgies for several years.

She did not have cyanosis or clubbing. Her pulse rate was 80 beats/min regular, blood pressure was 124/88 mm Hg, and her heart sounds were normal. On auscultation she had vesicular breath sounds with fine inspiratory bilateral basal crackles.

Routine haematological and biochemical parameters were normal. Her urinalysis was negative. Chest radiography showed diffuse bilateral air space consolidation, and electrocardiography was normal. Her forced expiratory volume in 1 second (FEV₁) and forced vital capacity (FVC) were 1.8 l (predicted 3.3 l) and 2.1 l (3.9 l), respectively.