Black Pleural Effusion as a Rare Presentation of Serotype 3 Pneumococcal Empyema.

Black pleural effusion (BPE) is exceptionally rare in children, with only 1 previously reported pediatric case linked to a pancreaticopleural fistula, while adult cases are typically associated with rupture of pancreatic pseudocysts, malignancy, fungal infection, or hemorrhage. A previously healthy, fully vaccinated 6-year-old boy presented with severe pneumonia, and thoracentesis/chest drainage revealed dark sanguineous, black fluid that tested positive by multiplex polymerase chain reaction for Streptococcus pneumoniae serotype 3, confirming empyema. He responded well to chest tube drainage, intrapleural fibrinolysis, and antibiotic therapy, and no underlying malignancy or pancreatic disease was identified. This case represents a rare instance of BPE caused by bacterial empyema in a child, expanding the pediatric differential diagnosis and underscoring that severe bacterial pneumonia-despite vaccination-can present with this unusual pleural fluid appearance.