What’s already known about this topic?
Interstitial lung disease (ILD) is one of the leading cause of mortality and morbidity for connective tissue disease. Immunosuppressive drugs are the main treatment for ILD. Cyclophosphamide (CYC) and azathioprine (AZA) are the leading treatment options for CTD-ILD and data related to those treatments mostly come from studies on scleroderma patients. Head to head comparison of CYC and AZA in first line treatment of CTD-ILD is also lacking.