Postpartum Spontaneous Hemothorax Strongly Suggestive of Thoracic Endometriosis Syndrome: A Case Report

A 34-year-old woman developed fever, dyspnea, and hypoxemia 8 days after vaginal delivery and was treated for pyelonephritis with bacteremia. The right dominant pleural effusion was initially clear and transudative, suggesting a systemic postpartum cause. However, sudden chest pain and worsening hypoxemia were followed by the rapid enlargement of the effusion, and repeat thoracentesis revealed hemothorax. Video-assisted thoracoscopic surgery revealed multiple small hematoma-like lesions on the visceral pleura. Markedly elevated pleural fluid CA-125 levels and pigment-laden macrophages suggested thoracic endometriosis syndrome. This case highlights that new hemorrhagic changes in postpartum pleural effusion warrant reassessment, including consideration of thoracic endometriosis syndrome.