Clinical Profiles and Lung Function Trajectories of Patients With Idiopathic Inflammatory Myopathy Associated Interstial Lung Disease: A Comparative Study of Pulmonology and Rheumatology Settings.

BACKGROUND

Idiopathic inflammatory myopathies (IIMs) are frequently complicated by interstitial lung disease (ILD). Although clinical heterogeneity is recognized, comparisons between patients with idiopathic inflammatory myopathy associated interstial lung disease (IIM-ILD) managed in pulmonology vs rheumatology centers remain limited.

RESEARCH QUESTION: Do differences in clinical features, treatment strategies, lung function trajectories, and transplant-free survival among patients with IIM-ILD followed at pulmonology or rheumatology centers exist?

STUDY DESIGN AND

METHODS

We conducted a multicenter, observational, cohort study including 75 patients with IIM-ILD diagnosed between 2014 and 2024: 25 from 2 Italian pulmonology centers and 50 from a rheumatology center in Norway. All met IIM classification criteria, had ILD confirmed by high-resolution CT scan, and had serial pulmonary function tests. Associations of baseline features, imaging patterns, and treatments with referral center were assessed using logistic regression. Lung function trajectories were assessed with linear mixed-effects models and transplant-free survival with Cox regression.

RESULTS

Patients with IIM-ILD from pulmonology centers were more often male, had more fibrotic ILD (OR, 5.61; 95% CI, 1.88-16.73; P = .002), had lower baseline diffusing capacity of the lungs for carbon monoxide (OR, 0.96; 95% CI, 0.93-0.99; P = .048), had less cutaneous (OR, 0.11; 95% CI, 0.03-0.40; P = .001) and musculoskeletal involvement, and used less rituximab (OR, 0.06; 95% CI, 0.01-0.23; P < .001) than patients from rheumatology centers. Despite baseline differences, both cohorts showed significant and comparable improvement in FVC and diffusing capacity of the lungs for carbon monoxide % predicted over a mean of 2.5 years. Transplant-free survival did not differ significantly between specialty centers. Factors associated with worse transplant-free survival included anti-MDA5 positivity (hazard ratio, 10.24; 95% CI, 1.70-61.66; P = .011), elevated C-reactive protein, and extensive lung fibrosis.

INTERPRETATION: Our results show that although baseline presentation and treatment characteristics of patients with IIM-ILD differed between rheumatology and pulmonology cohorts, transplant-free survival was comparable. Including patients from both pulmonology and rheumatology in future clinical trials may enhance representativeness without compromising data consistency.