Abstract Background Gaseous empyema (pyopneumothorax) is an uncommon variant of pleural infection characterized by the presence of both purulent fluid and gas within the pleural space. It is typically associated with gas-forming organisms, bronchopleural fistula, or prior thoracic instrumentation. We report a rare case of pyopneumothorax caused by Streptococcus viridans in a patient with metastatic lung cancer. Case Presentation A 56-year-old man with stage IV squamous cell carcinoma of the lung presented with five days of dyspnea, productive cough, pleuritic chest pain, and fever. He was tachypneic with decreased breath sounds over the right lung field. Laboratory results showed leukocytosis of 11,000/µL (84% neutrophils) and a C-reactive protein level of 110 mg/L. Chest CT demonstrated a large right-sided pleural effusion with multiple internal gas locules, consistent with gaseous empyema, without evidence of recent procedures or trauma (Images 1). A chest tube was inserted, draining thick purulent fluid. Pleural fluid Gram stain and culture grew Streptococcus viridans. Broad-spectrum antibiotics with piperacillin-tazobactam and teicoplanin were initiated. A follow-up CT scan revealed improved lung expansion and near-complete resolution of the effusion. Discussion This case is notable because Streptococcus viridans is not traditionally considered a gas-forming organism. In oncology patients, immunosuppression, tumor necrosis, and altered pleural immunity may predispose to atypical presentations of empyema. Early recognition of gaseous empyema is crucial, as delayed management can result in sepsis, bronchopleural fistula, trapped lung, or death. CT imaging plays a key role in diagnosis, particularly in distinguishing pyopneumothorax from hydropneumothorax or necrotizing pneumonia. Conclusion Gaseous empyema is a rare but serious condition that should be suspected when air-fluid levels are present in the pleural space without recent invasive interventions. This case expands the spectrum of causative organisms to include Streptococcus viridans and emphasizes the importance of early drainage and antimicrobial therapy, particularly in patients with lung cancer or immunocompromised states. This abstract is funded by: none
Alkharabsheh et al. (Fri,) studied this question.