Clinical impact of pneumomediastinum in patients with myositis-associated interstitial lung disease

Background: Idiopathic inflammatory myositis (IIM) frequently coexists with interstitial lung disease (ILD), significantly impacting morbidity and mortality. Spontaneous pneumomediastinum, a complication of myositis-associated ILD, remains understudied regarding its clinical implications. Method: We retrospectively reviewed patients diagnosed with myositis-associated ILD at Asan Medical Center, Seoul, South Korea, from April 2012 to September 2023. Patients were categorized into two groups based on the presence or absence of spontaneous pneumomediastinum during the follow-up period. Results: Among the 70 patients included in the study, the median age was 55.9 ± 12.2 years, with 62.9% being female. Pneumomediastinum developed in 12 (17.1%) patients. Clinical characteristics did not significantly differ between the pneumomediastinum and non-pneumomediastinum groups, except for the subtype of IIM. Notably, pneumomediastinum was observed in 11 (91.7%) patients with dermatomyositis and 1 (8.3%) with anti-synthetase syndrome (ASS), but none with polymyositis. Multivariate analysis revealed pneumomediastinum as a significant risk factor for mortality (hazard ratio: 2.829, 95% confidence interval: 1.100–7.270, p = 0.031) after adjusting for other variables. Patients with pneumomediastinum exhibited worse survival compared with patients without pneumomediastinum (median survival time: 77.7 ± 11.7 vs. 13.6 ± 3.7 months, p = 0.013). Conclusion: Spontaneous pneumomediastinum is an independent risk factor for mortality in patients with myositis-associated ILD.