Interstitial lung disease in patients with mixed connective tissue disease: pilot study on predictors of lung involvement.

OBJECTIVES: Mixed connective tissue disease (MCTD) is an immune-mediated systemic disorder characterised by serum autoantibodies against U1-ribonucleoprotein and diverse multisystemic clinical manifestations. Approximately 50% of patients with MCTD develop a radiologic pattern of interstitial lung disease (ILD). Our single centre, cross-sectional study sought to identify clinical and serologic associations of ILD in patients with MCTD which may serve as predictors of lung disease and prognosis.

METHODS: Patients who met validated criteria for diagnosis of MCTD were included in the study, and were further differentiated into study and control groups based on presence or absence of ILD.

RESULTS: Multivariate logistic regression showed an association of two clinical variables: dysphagia with an R2 value of 0.33 (p-value <0.001) and Raynaud's phenomenon with R2 value of 0.28 (p-value <0.001).

CONCLUSIONS: An association of dysphagia with the development of ILD in our study is in harmony with the existing literature. There are primarily case reports, suggesting an association of Raynaud's phenomenon with development of ILD in patients with undifferentiated CTD. To our knowledge, this is the first study highlighting the association of Raynaud's phenomenon with development of ILD in patients with MCTD. The mechanistic aspects of the association between Raynaud's phenomenon and ILD remain unexplored. The association of easily elicited historical and clinical features of MCTD with subtle, but worrisome, pulmonary pathology carries the promise of sensitising the unsuspecting clinician about the entity of ILD in MCTD.