Case Report: Suspected Mycobacterium abscessus-associated polyserositis following coronary stenting, diagnosed with the aid of metagenomic next-generation sequencing.

BACKGROUND: Mycobacterium abscessus (M. abscessus), a rapidly growing non-tuberculous mycobacterium (NTM), rarely causes extrapulmonary disease involving more than one serosal compartment. CASE PRESENTATION: An 83-year-old man developed intermittent fever about 6 weeks after coronary stent implantation. Multiple antibiotics were ineffective, and he was admitted for fever of unknown origin. Echocardiography showed newly developed pericardial adhesion with echocardiographic changes suggestive of possible early constrictive physiology. These were absent on the echocardiogram performed on the day of percutaneous coronary intervention. During admission, he underwent surgery for mechanical small-bowel obstruction, in which dense omental adhesions were found. With no prior abdominal surgery, the synchronous pericardial, pleural, and peritoneal abnormalities raised suspicion of a systemic inflammatory or infectious process. A single blood-culture draw at the outside hospital grew coagulase-negative staphylococcus, but blood cultures repeated after admission and a bone-marrow culture were negative. Blood metagenomic next-generation sequencing (mNGS) detected M. abscessus at very low abundance (three species-level reads, below the ≥8-read threshold), reported as a suspected organism. Temperature improved during the administration of agents with recognized activity against M. abscessus (linezolid, tigecycline) and relapsed during the administration of β-lactams not active against this organism. Integrating the clinical course, treatment response, and consultation from a tuberculosis specialty hospital, a clinically suspected diagnosis of M. abscessus infection supported by mNGS was made, although microbiological confirmation was not obtained. Temperature normalized on tigecycline and the patient's condition improved, and he was transferred for continued anti-NTM therapy. He was subsequently lost to follow-up, and therefore, the long-term outcome is unknown. CONCLUSION: We report a rare presentation of suspected M. abscessus-associated polyserositis following coronary stenting, in which mNGS provided the etiologic clue when cultures were unrevealing. NTM should be considered in older patients with unexplained fever after cardiovascular intervention. Low-abundance mNGS results, although below reporting thresholds, may be clinically meaningful when interpreted alongside the clinical course and treatment response, while remaining open to contamination and misclassification. NTM-associated myeloperoxidase-antineutrophil cytoplasmic antibody positivity is non-specific and must be distinguished from primary vasculitis.