Connective tissue diseases are known to be one of the causes of organising pneumonia (OP). However, this association is rare and signs of OP usually occur in the context of an already diagnosed disease. We report three cases of OP preceding the articular symptoms of the underlying connective tissue disease by 3–6 months in two cases of rheumatoid arthritis and by 36 months in one patient with primary Sjögren's syndrome. The diagnosis of post-infectious OP had initially been suspected in the three cases and the patients had not been followed up further. The occurrence of OP preceding articular or any other extrapulmonary involvement of connective tissue disease had been reported in only four cases in the literature and, to our knowledge, no case preceding Sjögren's syndrome had ever been reported. These observations suggest that exhaustive investigations should be considered when OP is diagnosed, including antinuclear auto-antibodies and investigations for Sjögren's syndrome, even when there are no clinical signs suggesting an underlying connective tissue disease. These investigations should also be repeated during the course of the disease, especially in the case of OP continuing to progress under treatment and, of course, if signs of connective tissue disease appear.

FENO could be a tool for differentiating chronic HP from other types of pulmonary fibrosis. The mechanism involved seems to be bronchiolar disease.

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