Objective. In patients with interstitial lung disease (ILD) associated with connective tissue disease (CTD), chronic ILD related symptoms may often dominate the clinical picture or precede systemic findings and thus often be seen by a non-rheumatologist. The purpose of this study was to evaluate the importance of rheumatologic consultation during ILD work up.
Methods. We retrospectively reviewed 64 patients with ILD from a single tertiary center for their clinical and laboratory characteristics, rheumatologic consultation status, and result of the consultation. American College of Rheumatology criteria for classification of each connective tissue disease were utilized. Undifferentiated connective tissue disease (UCTD) was classified by pre-specified criteria.
Results. A total of 23 (36%) of the ILD patients had associated CTD. Five (8%) patients had underlying CTD before the diagnosis of ILD, whereas 18 (28%) patients were diagnosed with CTD after the rheumatologic consultation. ILD patients with CTD were predominantly female, had significantly more frequent radiographic diagnoses of nonspecific interstitial pneumonia, increased frequencies of high titer antinuclear antibody positivity, and rheumatoid factor positivity. Rheumatologic consultation was referred in 36 (56%) patients. In 18 (50%) of the referred patients, CTD was diagnosed. In 61% of the patients diagnosed with CTD as a result of rheumatologic consultation, changes in therapy occurred.
Conclusion. A substantial proportion of patients with ILD are found to have an underlying CTD upon evaluation by a rheumatologist. Since ILD associated with CTD mimics idiopathic interstitial pneumonia, rheumatologic consultation may have a significant impact on the clinical care of ILD.

Keywords: Interstitial lung disease, Connective tissue diseases, Rheumatologic consultation