Rapidly progressive pulmonary abscess initially misdiagnosed as lung cancer: the role of Peptostreptococcus stomatis and Parvimonas micra.

Pulmonary abscess is a serious infectious disease characterized by localized lung tissue necrosis, primarily caused by anaerobic or facultative anaerobic bacterial infections. While the Streptococcus anginosus group (SAG) is a well-established pathogen in pulmonary abscess formation, recent findings suggest that strict anaerobes such as Peptostreptococcus stomatis and Parvimonas micra can also contribute to deep-seated infections. However, their role in rapidly progressive pulmonary abscesses has not been previously documented. Here, we present a case of a rapidly progressive pulmonary abscess caused by Peptostreptococcus stomatis and Parvimonas micra in an immunocompetent patient, initially misdiagnosed as lung cancer. This case highlights the importance of differentiating infectious lung lesions from malignancies and underscores the clinical utility of metagenomic next-generation sequencing (mNGS) in diagnosing rare anaerobic infections, offering valuable insights for precise diagnostic and therapeutic strategies.