Clinical phenotype and prognostic determinants of spontaneous pneumomediastinum in anti-MDA5 antibody-positive dermatomyositis.

INTRODUCTION

To identify the clinical phenotype and prognostic determinants in patients with anti-MDA5 antibody-positive dermatomyositis (MDA5+DM) with spontaneous pneumomediastinum (SPM).

METHODS

We retrospectively analyzed 150 MDA5+DM patients (50 with SPM and 100 without). Clinical, laboratory, and therapeutic profiles were analyzed. Multivariable logistic regression was used to identify factors associated with survival in the SPM cohort.

RESULTS

The SPM group had a significantly higher 6-month mortality than the non-SPM group (54% vs. 16%, P<0.001). Patients with SPM were older and less frequently had arthralgia, and exhibited a hyper-inflammatory phenotype [elevated CRP, serum ferritin (SF), LDH, neutrophil-to-lymphocyte ratio (NLR), KL-6], severe lymphopenia, and higher infection rates. Prior calcineurin inhibitor (CNI) use was more common in the non-SPM group (85% vs. 62%, P = 0.001). Within the SPM group, non-survivors had shorter disease duration and higher inflammatory markers. Multivariable analysis identified longer pre-SPM disease duration (OR 0.479, 95% CI 0.266-0.863) and prior cyclophosphamide (CTX) therapy (OR 0.034, 95% CI 0.003-0.405) as factors independently associated with improved survival (both P<0.05).

CONCLUSION

Older MDA5+DM patients with a hyper-inflammatory phenotype and fewer arthralgias are at increased risk for SPM, whereas prior CNI use may be protective. In SPM patients, elevated inflammatory markers predict poor survival, while longer pre-SPM disease duration and prior CTX therapy are associated with improved survival, suggesting early aggressive immunosuppression may improve outcomes.