A rare case of disseminated Mycoplasma pneumoniae infection spreading from a pelvic lesion to a psoas muscle abscess

OBJECTIVES: Extrapulmonary infections caused by Mycoplasma pneumoniae are uncommon, and their manifestation as soft tissue abscesses is particularly rare. Diagnosing such culture-negative infections in immunocompromised hosts poses a significant clinical challenge. This study reports a case of M. pneumoniae-induced soft tissue abscesses in an immunocompromised patient, highlighting the diagnostic utility of advanced microbiological techniques. METHODS: We retrospectively analyzed the clinical course of a 17-year-old female with aplastic anemia and a history of haploidentical hematopoietic stem cell transplantation, who presented with recurrent fever and pelvic/psoas abscesses. Metagenomic next-generation sequencing (mNGS) was performed on abscess drainage to identify the causative pathogen and its resistance profile. RESULTS: mNGS of the abscess fluid identified M. pneumoniae as the dominant pathogen and revealed a macrolide-resistant 23S rRNA A2063G mutation. Consequently, targeted antimicrobial therapy with tigecycline and omadacycline was administered, which led to the resolution of clinical symptoms. CONCLUSION: This case underscores the critical role of mNGS in the accurate diagnosis of culture-negative extrapulmonary infections. Furthermore, it demonstrates how mNGS-guided resistance profiling can inform effective antimicrobial therapy in immunocompromised patients.