A 64-yr-old male with a longstanding history of psoriatic arthritis presented with a 6-week history of dry cough without other respiratory symptoms. His other past medical history showed hypertension and type II diabetes mellitus. He took methotrexate 12.5 mg weekly (commenced 9 yrs previously), folic acid, aspirin, nortriptyline, metformin, valsartan and insulin. The patient was an ex-smoker of 5 pack-yrs, having stopped smoking 32 yrs earlier. He kept no pets and there was no significant occupational exposure or travel history. On examination his chest was clear. There was no lymphadenopathy or clubbing.
A chest radiograph (fig. 1⇓) showed multiple pulmonary nodules. C-reactive protein was 6 mg·L−1, erythrocyte sedimentation rate was 17 mm·h−1 and white blood cell count was 13×109 cells·L−1 …