Background/Purpose: Patients with anti-PM-Scl antibody (PM-Scl) can present with several different phenotypes: polymyositis (PM), dermtomyositis (DM), systemic sclerosis (SSc), scleromyositis, or sclero-dermatomyositis. Interstitial Lung Disease (ILD) is a disease manifestation of SSc and PM/DM. However, characteristics of ILD in patients with PM-Scl have not been characterized in the published literature.

Methods: All patients screened for PM-Scl between October 1999 and April 2014 were evaluated through our electronic medical record (EMR) and patients with positive PM-Scl were identified. Data on demographics, rheumatologic diagnoses (PM, DM, SSc, PM-SSc, DM-SSc), and high resolution computed tomography (HRCT) defined interstitial lung disease (ILD) were extracted from their EMR. Available HRCT images were reviewed by a thoracic radiologist with expertise in ILD (RY). Radiographic diagnoses on thoracic HRCT scan [cellular non-specific interstitial pneumonia (NSIP), fibrotic NSIP, usual interstitial pneumonia (UIP), and organizing pneumonia (OP)] were determined. The degree of parenchymal inflammation and fibrosis were scored using the criteria defined by Ooi (Acta Radiologica. 2003;44:258-264) Comparisons between initial and follow-up scans were performed using Wilcoxon signed rank tests.

Results: PM-Scl was detected in 42 patients. Of these, ILD was described on HRCT scan in 27 patients (64.2%). HRCT images were available for review in 23 patients; 17 (73.9%) were female. The rheumatologic diagnoses of these patients include diffuse cutaneous SSc (dcSSc) (n=1), limited cutaneous SSc (lcSSc) (n=4), PM (n=6), DM (n=3), overlap of dcSSc and DM (n=1), overlap of lcSSc and PM (n=2), overlap of lcSSc and DM (n=4) and other diagnoses (n=2). HRCT diagnoses of these 23 patients include fibrotic NSIP (n=13), cellular NSIP (n=6), organizing pneumonia (OP) (n=2), UIP (n=1), and bronchiolitis (n=1). Fifteen patients had follow-up HRCT images available after a mean interval of 46.5 months. The initial HRCT scans indicated fibrotic NSIP (n=8), cellular NSIP (n=5) and OP (n=2). Of the 5 patients with initial cellular NSIP, 3 patients continued as cellular NSIP and 2 progressed into fibrotic NSIP. Two patients with initial OP developed fibrotic NSIP on follow up HRCT scan. The mean total HRCT score on the initial scan was 6 and the mean HRCT score on the follow up scan was 6.6 (P=0.14). The mean inflammation score on the initial scan was 4.9 and that of fibrosis score was 1.1. On the follow up HRCT scan the inflammation score was 4.4 (P=0.41) and the fibrosis score was 2.2 (P=0.063). All patients received immunosuppressive therapy including glucocorticoids (n=15), azathioprine (n=10), mycophenolate mofetil (n=4), methotrexate (n=3), tacrolimus (n=2), rituximab (n=2), leflunomide (n=2), cyclophosphamide (n=1) and intravenous immunoglobulin (n=4).   

Conclusion: NSIP was the predominant HRCT-based subtype of ILD in our cohort of patients with PM-Scl. All patients received immunosuppressive therapy. The total lung score did not change significantly over a mean follow-up period of 46.5 months but fibrosis score showed an upward trend over the study period.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/interstitial-lung-disease-in-patients-with-anti-pm-scl-antibody/