Polymyositis–Dermatomyositis-associated Interstitial Lung Disease

TLDR

Treatment consisted of high‑dose prednisone (40–60 mg/d) for initial control, followed by a taper with a lower dose plus an immunosuppressant such as azathioprine or methotrexate for disease suppression. In 70 patients with polymyositis or dermatomyositis and diffuse interstitial lung disease, the predominant presentations were musculoskeletal or pulmonary symptoms, imaging revealed bilateral irregular linear opacities, Jo‑1 antibodies were present in 38 % of those tested, lung biopsies showed nonspecific interstitial pneumonia in 82 % of cases, and survival was better than that of idiopathic UIP and comparable to idiopathic NSIP, with no difference between Jo‑1 positive and negative groups.

Abstract

We report findings in 70 patients with both diffuse interstitial lung disease and either polymyositis (PM) or dermatomyositis (DM). Initial presentations were most commonly either musculoskeletal (arthralgias, myalgias, and weakness) or pulmonary (cough, dyspnea, and fever) symptoms alone; in only 15 patients (21.4%) did both occur simultaneously. Pulmonary disease usually took the form of acute to subacute antibiotic-resistant community-acquired pneumonia. Chest radiographs and computed tomography most commonly demonstrated bilateral irregular linear opacities involving the lung bases; occasionally consolidation was present. Jo-1 antibody was present in 19 (38%) of 50 patients tested. Synchronous associated malignancy was present in 4 of 70 patients (5.7%). Surgical lung biopsies disclosed nonspecific interstitial pneumonia (NSIP) in 18 of 22 patients (81.8%), organizing diffuse alveolar damage (DAD) in 2, bronchiolitis obliterans organizing pneumonia (BOOP) in 1, and usual interstitial pneumonia (UIP) in 1. Treatment usually included prednisone in 40-60 mg/d dosages for initial control, followed by lower dose prednisone plus an immunosuppressive agent such as azathioprine or methotrexate for disease suppression. Survival was significantly better than that observed for historical control subjects with idiopathic UIP, and was more consistent with survival previously reported in idiopathic NSIP. There was no difference in survival between Jo-1 positive and Jo-1 negative groups.