Case Report: Torque teno virus identified in pleural effusion of pediatric severe Mycoplasma pneumoniae pneumonia: diagnostic and therapeutic implications.

Mycoplasma pneumoniae pneumonia (MPP) is a common cause of community-acquired pneumonia (CAP) in school-aged children, among whom 1%-20% may develop pleural effusion. Most effusions are small in volume and self-resolving. We report two pediatric cases of severe MPP complicated by massive pleural effusion that were unresponsive to initial anti-mycoplasma therapy. Targeted next-generation sequencing (tNGS) of pleural fluid identified macrolide-resistant Mycoplasma pneumoniae and Torque teno virus (TTV) in both cases. Both patients recovered after closed thoracic drainage, adjustment of anti-mycoplasma therapy according to resistance findings, and adjunctive immunomodulatory treatment. These cases indicate that, in severe MPP with massive pleural effusion, pleural-fluid tNGS may provide useful diagnostic information beyond conventional testing, including the identification of macrolide resistance and additional viral findings such as TTV. However, given the high background prevalence of TTV in humans and the absence of control samples in this report, the clinical significance of TTV detection in pleural fluid remains uncertain. At present, TTV is more appropriately interpreted as a possible biomarker of immune perturbation or disease severity rather than a confirmed pathogenic driver. Broader pathogen testing in selected specimens such as pleural fluid may complement diagnostic evaluation in complex infections, but larger controlled studies are needed to clarify the significance of TTV in this setting.