摘要Background Interstitial lung disease (ILD) is a serious lung complication in polymyositis (PM) and dermatomyositis (DM) which affects prognosis and requires a more aggressive approach in therapy. This study investigated the prevalence, characteristics, predictive factors and unfavourable prognostic factors of ILD in newly diagnosed PM, DM and amyopathic DM (ADM). Methods From January 2000 to December 2008, the medical records of 197 consecutive PM and DM patients at the Second Affiliated Hospital of Sun Yat-Sen University were reviewed excluding overlapping, juvenile, and malignancy-associated cases. The patients were assigned to an ILD (69 patients) and a non-ILD group (128 patients). The clinical features, laboratory findings, and prognosis were compared. Results The multivariate analysis indicated that older age at onset (OR 1.033, 95%CI 1.009-1.058, P=0.007), fever (OR 4.109, 95%CI 1.926-8.767, P<0.001) and arthritis/arthralgia (OR 2.274, 95%CI 1.101-4.695, P=0.026) were the independent predictive factors for developing ILD in PM/DM after excluding anti-Jo-1. Regarding anti-Jo-1, fever (OR 4.912, 95%CI 2.121-11.376, P<0.001) was associated with ILD. Poor survival in ILD patients was associated with ILD clinical subset (RR 0.122, 95%CI 0.049-0.399, P<0.001), ADM/DM/PM-ILD (RR 0.140, 95%CI 0.031-0.476, P=0.002), cardiac involvement (RR 4.654, 95%CI 1.391-15.577, P=0.013) and serum albumin level (RR 0.910, 95%CI 0.831-0.997, P=0.042). Conclusions Patients who presented with fever tended to have a higher frequency of PM/DM-associated ILD. A Hamman-Rich-like presentation, ADM-ILD, cardiac involvement and hypoalbuminemia were poor prognostic factors in ILD-PM/DM.