Rheumatoid arthritis and cryptogenic organising pneumonitis.

We describe three patients with rheumatoid arthritis who presented with non-specific pulmonary symptoms, a restrictive defect in lung function and bilateral changes on chest radiograph. Lung histology showed characteristic features of cryptogenic organising pneumonitis and treatment with steroids produced significant improvement. The clinical and laboratory features of cryptogenic organising pneumonitis (otherwise known as bronchiolitis obliterans organising pneumonia, 'BOOP') are discussed and compared with those of bronchiolitis obliterans with which the condition should not be confused. Cryptogenic organising pneumonitis should be considered as one of the pulmonary manifestations of rheumatoid arthritis, but lung biopsy is essential to make the diagnosis.