Abstract
Spontaneous pneumomediastinum is a recognized complication of connective tissue disease associated interstitial lung disease, most extensively described in dermatomyositis. Despite rheumatoid arthritis being the most common connective tissue disease with pulmonary involvement, spontaneous pneumomediastinum in rheumatoid arthritis associated lung disease has been reported only once previously. Rheumatoid arthritis uniquely causes two distinct forms of structural lung injury (interstitial lung disease and bronchiectasis) both linked to seropositive autoimmunity. An 83-year-old woman, a never-smoker with seropositive rheumatoid arthritis, progressive pulmonary fibrosis, left lower lobe bronchiectasis, low body mass index, and iatrogenic lymphopenia developed extensive pneumomediastinum during community-acquired pneumonia. Computed tomography scan demonstrated pneumomediastinum with subcutaneous emphysema, emphysematous lungs with diffuse interstitial scarring, bronchiectasis, and lobar consolidation. Conservative management with antibiotics achieved complete radiographic resolution at 8 weeks with no recurrence at 12 weeks. We hypothesize a three-component pathophysiologic framework: structural alveolar fragility from interstitial lung disease and emphysema may provide the substrate for alveolar rupture, while infection-driven coughing from true airway bronchiectasis may serve as the mechanical trigger via the Macklin effect. In rheumatoid arthritis, all three components appear driven by a shared seropositive autoimmune process. This mechanistic profile may differ fundamentally from dermatomyositis, where spontaneous pneumomediastinum is thought to reflect rapidly progressive parenchymal destruction, suggesting that dermatomyositis-derived mortality data may not be directly applicable to rheumatoid arthritis. Spontaneous pneumomediastinum in seropositive rheumatoid arthritis may follow a favourable trajectory when the mechanical trigger is reversible. High titer seropositivity, low body mass index, and iatrogenic immunosuppression may identify a convergent risk phenotype.