Abstract Introduction Idiopathic Inflammatory Myopathy Associated Interstitial Lung Disease (IIM-ILD) can be the initial presentation for myositis. Conversely, systemic autoimmune rheumatic diseases-associated intestinal lung diseases (SARD-ILD) typically progress after the onset of a systemic rheumatic disease. However, there exists another subset of patients with positive myositis associated antibodies (MAAs) and myositis specific antibodies (MSAs) and ILD but no other rheumatological symptoms. The 2023 ACR/CHEST guidelines regarding management for IIM-ILD and SARD-ILD do not address patients with positive antibodies with no other systemic rheumatological symptoms. This study aimed to see whether there were any significant differences in baseline characteristics and outcomes between patients with IIM-ILD and those with SARD-ILD or undifferentiated patients with positive MSA or MAA antibodies. Methods A retrospective chart review from 2014 to 2025 at a quaternary academic center identified adults diagnosed with ILD and positive MSAs or MAAs. One hundred twenty-one patients were identified with primary outcomes including changes in pulmonary function tests, need for transplant, and overall mortality. Patients were categorized as either having rheumatologist-diagnosed IIM-ILD or positive MSA or MAA antibodies without a formal diagnosis. Chi-Squared and Fisher Exact Test were used to compare categorical variables, while Mann-Whitney U-Test was done to compare continuous variables. Results Twenty-nine patients had IIM-ILD, and 92 patients had positive MSA or MAA antibodies. At baseline, patients diagnosed with IIM-ILD were significantly younger (p 0.001), less likely to have a history of smoking (p = 0.04), and more frequently positive for an MSA antibody (p 0.001). There was no statistically significant difference in gender and race between the two groups. In terms of quantitative CT analysis, there was evidence of more consolidation (p = 0.029) in the myositis group and a trend towards increased reticulation (p = 0.064) with no statistically significant difference in the amount of ground glass opacities or honeycombing. For primary outcomes, there was no statistically significant difference in change in forced vital capacity (FVC) or diffusing capacity of the lungs for carbon monoxide (DLCO) or difference in mortality. Patients with IIM-ILD were less likely to be treated with anti-fibrotic therapy (p = 0.042). Conclusion Although individuals diagnosed with a clinical IIM presented at a younger age, there was no difference in the amount of quantitative fibrosis or outcomes. Therefore, patients who test positive for MSA or MAA antibodies with evidence of ILD should be treated similarly to those with IIM-ILD. This abstract is funded by: None
Mittal et al. (Fri,) studied this question.
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