Disseminated Culture-Negative Periprosthetic Knee Infection With Multifocal Septic Arthritis Associated With...

We report a case of a 72-year-old woman with Waldenström macroglobulinemia who developed a culture-negative periprosthetic joint infection (PJI) of the right knee following total knee arthroplasty. Despite multiple debridements and broad-spectrum antibiotics, she developed systemic signs of infection and hematogenous spread to multiple native joints, including the contralateral knee, ankle, wrist, and lumbar facet joints. All intraoperative cultures remained negative. A respiratory PCR was performed, which detected Mycoplasma pneumoniae, and metagenomic next-generation sequencing (mNGS) of plasma supported the diagnosis of the pathogen. Based on these findings, therapy was narrowed to doxycycline, resulting in clinical improvement and deferral of further surgery. This case highlights the importance of considering atypical pathogens in culture-negative PJI and demonstrates the utility of mNGS in guiding targeted antimicrobial therapy.