Objective: To investigate the clinical manifestation and prognostic factors of interstitial lung disease (ILD) in Korean patients with idiopathic inflammatory myopathies include with polymyositis (PM) and dermatomyositis (DM). Methods: Clinical and laboratory data of 110 patients with PM/DM in our rheumatology clinic were investigated. Clinical data including history, medication, pulmonary function tests (PFT) findings, radiologic findings, and labaratory findings were obtained from medical records at the first diagnosis of ILD with PM/DM. ILD was diagnosed on the basis of the imaging abnormalities defined above on definite findings of chest X-rays and high resolution computed tomography (HRCT), restrictive changes on PFT with respiratory symptoms. During the course of treatment, we assessed chest radiograph and HRCT findings. Results: Forty-two PM/DM patients (38.2%) developed ILD. Anti-extracellular nuclear antigen (ENA) antibody, anti-Jo-1 antibody and ground glass opacity in HRCT were significantly high in PM-ILD. However honeycoomb appearance (53%：22%) and fibrosis (41%：6%) in HRCT were significantly high in DM-ILD. Interest in aspects of prognosis including initial steroid treatment response in HRCT were favorable in PM-ILD. There were statistically significant association between normal level of CPK and usual interstitial pneumonia (UIP) pattern in HRCT in DM-ILD. Such cases had resistance to steroid therapy. Overall interval between steroid and immunosuppressant therapy was significantly shorter in those with DM-ILD. Conclusion: The clinical manifestations between PM-ILD and DM-ILD in Korean patients were not significant different from those of other populations. DM-ILD is more refractory to steroid treatment, expecting in poor prognosis compared with PM-ILD. So immediate intensive immunosuppressive therapy should be considered in DM-ILD.

Keywords: Interstitial lung disease, Inflammatory myositis, Polymyositis, Dermatomyositis