Rheumatoid Pleuropulmonary Disease Mimicking Refractory Empyema: A Diagnostic Challenge With Trapped Lung.

Rheumatoid arthritis (RA)-related pleural disease is an uncommon but serious extra-articular complication that can closely mimic empyema. Rheumatoid pleural effusions are exudative, with low pH, markedly reduced glucose, and elevated lactate dehydrogenase (LDH), and the fluid may appear green and frankly purulent, a constellation that overlaps substantially with infected parapneumonic effusion, particularly when cultures are negative. We report a 66-year-old woman with a 22-year history of seropositive, erosive, nodular RA who presented with recurrent right-sided pleural effusions and progressive dyspnea over three years. She was initially diagnosed with empyema following a presumed ruptured pleural-based pulmonary abscess. Pleural fluid was an exudate with elevated LDH (1,364 U/L), low glucose (45 mg/dL), and a lipid profile consistent with a chronic pseudochylous effusion, and repeated bacterial, mycobacterial, and fungal cultures were sterile. Video-assisted thoracoscopic surgery (VATS) with pleural and lung biopsies demonstrated findings characteristic of RA-related lung disease, including fibrinous pleuritis, follicular bronchiolitis, and a usual interstitial pneumonia (UIP) pattern. Because the lung remained trapped by a fibrous peel, staged thoracotomy with decortication and parietal pleurectomy was performed, and immunosuppression was escalated from leflunomide to rituximab. Detailed long-term follow-up data were not available for inclusion in this report. This case illustrates that in a patient with established RA, an exudative, culture-negative, purulent-appearing pleural effusion should raise suspicion of rheumatoid pleuritis before empyema. Early recognition, alongside continued exclusion of infection, may reduce diagnostic delay and the need for extensive thoracic surgery.