Purpose: The purpose of this study was to investigate whether systemic lupus erythematosus (SLE) patients with interstitial lung disease represent a particular subset of patients characterized by the presence of clinical, serologic, and nailfold capillary patterns overlapping scleroderma.
Patients and methods: In 57 consecutive patients with SLE, a standardized detailed history was obtained and a physical examination performed, directed at signs and symptoms of connective tissue diseases, in particular scleroderma. Additionally, pulmonary function testing, chest radiography, radionuclide transit studies of the esophagus, nailfold capillary microscopy, and detailed serologic studies directed at the antigenic specificities of antinuclear antibodies were performed. Patients were divided into three groups based on the results of pulmonary function testing, i.e., normal lung function, restriction, or isolated impairment of diffusion. Clinical, serologic, and nailfold capillary microscopic findings were compared among these three groups.
Results: Twenty patients had normal lung function, 19 had restrictive lung function loss, and 9 had an isolated impairment of the diffusing capacity (T1,CO). Patients with obstructive lung disease (n = 9) were excluded from analysis. Sclerodermatous changes of the hands were associated with a restrictive lung function pattern. Interstitial changes on chest radiograph were associated with isolated impairment of T1,CO. Nailfold capillary abnormalities correlated with decreased T1,CO and Dm, the component of T1,CO representing the diffusing capacity of the alveolocapillary membrane. Antibodies to U1-RNA were associated with restrictive lung function and decreased T1,CO.
Conclusion: We conclude that interstitial lung disease is present in a subset of SLE patients characterized by an increased prevalence of scleroderma traits and anti-(U1)RNA antibodies. Microvascular changes may contribute to the development of interstitial lung disease in SLE as well as in scleroderma.