Clinical features of polymyositis/dermatomyositis with steroid-resistant interstitial lung disease

Polymyositis and dermatomyositis (PM/DM) without creatine kinase (CK) elevation shows a poor prognosis. PM/DM is complicated with interstitial lung disease (ILD), some of which progress rapidly. To clarify the clinical features of PM/DM from the viewpoint of ILD progression, the clinical data of 25 PM/DM patients with ILD were reviewed. They were classified as responders or non-responders. The patients whose ILD responded to steroid therapy and elicited good clinical courses were termed as responders. On the other hand, the patients who had rapidly progressive ILD resistant to steroid therapy were considered as non-responders. The patients diagnosed to have DM were likely to be steroid-resistant. The non-responder group revealed significantly high aspartate aminotransferase (AST), low CK, low white blood cell (WBC), and low absolute lymphocyte counts in their peripheral blood. High CK/AST may be a favorable predictor of the disease. The percentages of lymphocytes in bronchoalveolar lavage fluid were increased in both groups. However, the percentages of two responders with low CK/AST were lower than those of three non-responders. A steroid-resistant ILD group with PM/DM may be clinically different from a steroid-responsive ILD group.