Predictive factors and unfavourable prognostic factors of interstitial lung disease in patients with polymyositis or dermatomyositis: a retrospective study.

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.