Differences in clinical features and prognosis of interstitial lung diseases between polymyositis and dermatomyositis

Objective. To assess the difference in clinical features and prognosis of patients with interstitial lung disease (ILD) comparing polymyositis (PM) and dermatomyositis (DM). Methods. Medical records of 28 ILD patients with PM/DM (16 PM-ILD, 12 DM-ILD) were reviewed retrospectively. Results. Serum CPK concentrations were significantly higher in PM-ILD than in DM-ILD. Bronchoalveolar lavage analysis showed that the percentages of lymphocytes and eosinophils were significantly higher in DM-ILD than in PM-ILD. Ten patients (5 PM-ILD, 5 DM-ILD) underwent surgical lung biopsy, and 3 (3 DM-ILD) had an autopsy. Nonspecific interstitial pneumonia (NSIP) was found in 7 (4 PM-ILD, 3 DM-ILD) and usual interstitial pneumonia (UIP) in 3 (1 PM-ILD, 2 DM-ILD). Interestingly, diffuse alveolar damage (DAD) was found in 3 patients with DM-ILD, who. all died of deterioration of ILD; but no one with PM-ILD had DAD. Corticosteroid treatment alone achieved a favorable response in 6 patients (37.5%) with PM-ILD, but in only one (8.3%) with DM-ILD. Administration of cyclosporine in the early phase of onset benefited 4 corticosteroid-resistant patients with DM-ILD. Conclusively, survival in DM-ILD was significantly worse than that in PM-ILD. Conclusion. DM-ILD is more refractory to corticosteroid therapy, resulting in poorer prognosis compared with PM-ILD. These data indicate that intensive therapy, including cyclosporine, should be considered for DM-ILD.