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 <i>Streptococcus anginosus group</i> (SAG) is a well-established pathogen in pulmonary abscess formation, recent findings suggest that strict anaerobes such as <i>Peptostreptococcus stomatis</i> and <i>Parvimonas micra</i> 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 <i>Peptostreptococcus stomatis</i> and <i>Parvimonas micra</i> 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.