Predictive factors for long-term outcome in polymyositis/dermatomyositis-associated interstitial lung diseases

Abstract Background Interstitial lung disease (ILD) is strongly associated with polymyositis (PM), dermatomyositis (DM), and clinically amyopathic dermatomyositis (CADM). It is also related to mortality. Previous studies have highlighted that the acute form of PM/DM/CADM-associated ILD (PM/DM/CADM-ILD) has a poor short-term prognosis. However, little is known about the long-term clinical features of patients with PM/DM/CADM-ILD. The aim of the present study is to clarify the clinical characteristics and the predictive factors for long-term outcomes in patients with PM/DM/CADM-ILD. Methods Thirty-four patients with PM/DM/CADM-ILD who were followed up for more than 12 months were analyzed retrospectively. The patients were classified as “stable” or “deterioration” according to respiratory symptoms, serial changes in forced vital capacity (FVC) or arterial oxygen pressure, and radiologic findings during the follow-up period. Results Twenty-six patients (76%) were in the stable group and eight patients (24%) were in the deterioration group. Home oxygen therapy was performed in six cases in the deterioration group because of chronic respiratory failure due to progression of ILD. The deterioration group, in comparison to the stable group, had a significantly lower %FVC and a higher positive rate for the anti-PL-7 antibody. Multivariate logistic regression analysis revealed that a positive anti-PL-7 antibody test and a lower %FVC were independently associated with deterioration during long-term follow-up. Conclusions Patients with PM/DM/CADM-ILD are at risk for chronic respiratory failure due to the deterioration of ILD during long-term follow-up. The presence of anti-PL-7 antibody and a lower %FVC at initial diagnosis may predict long-term deterioration in patients with PM/DM/CADM-ILD.