AbstractLung disease is common in patients with rheumatoid arthritis (RA). The onset of lung involvement in RA is not well known. The objective is to describe the features and evolution of lung involvement in early RA, its relationship with disease activity parameters, smoking and treatments. Consecutive patients with early RA without respiratory symptoms were included and tracked for 5 years. Lung assessment included clinical, radiological and pulmonary function tests at diagnosis and during follow-up. Peripheral blood parameters (erythrocyte sedimentation rate, C reactive protein, rheumatoid factor and anti-citrullinated peptide autoantibodies) and scales of articular involvement, such as DAS28-CRP, were evaluated. 40 patients were included and 32 completed the 5-year follow up. 13 patients presented lung involvement in the initial 5 years after RA diagnosis, 3 of them interstitial lung disease. Significant decrease of diffusion lung transfer capacity of carbon monoxide over time was observed in six patients, 2 of them developed interstitial lung disease. DLCO decrease was correlated with higher values of CRP and ESR at diagnosis. Methotrexate was not associated with DLCO deterioration or lung disease development. Subclinical progressive lung disease correlates with RA activity parameters. Smoking status and methotrexate were not associated with development or progression of lung disease.