Spinal Tuberculosis Diagnosed by Metagenomics Capture (MetaCAP) in a Patient Undergoing Maintenance Hemodialysis: A...

BACKGROUND Spinal tuberculosis is difficult to diagnose in patients undergoing maintenance hemodialysis (MHD) because of immunosuppression, atypical clinical manifestations, and the limited sensitivity of conventional microbiological assays. Rapid and accurate pathogen identification is essential to distinguish spinal tuberculosis from other causes of vertebral destruction, including metastatic malignancy and bacterial spondylitis. This report aims to illustrate the diagnostic value of capture-based targeted sequencing for detecting Mycobacterium tuberculosis in extrapulmonary infection when routine tests and metagenomic next-generation sequencing (mNGS) yield inconclusive or misleading results. CASE REPORT A 64-year-old woman with end-stage renal disease secondary to IgA nephropathy, receiving long-term MHD, presented with progressive low back pain. Imaging revealed multilevel vertebral involvement with pathological fractures, raising suspicion of metastatic disease or infectious spondylitis. Histopathological examination demonstrated granulomatous inflammation, while acid-fast staining and routine cultures were negative. Initial mNGS of spinal tissue identified Staphylococcus aureus, leading to targeted antibacterial therapy. Although inflammatory markers declined, the patient's symptoms worsened and pancytopenia developed. Subsequent analysis of spinal pus using metagenomic capture (MetaCAP)-based targeted sequencing detected the Mycobacterium tuberculosis complex with high confidence. Anti-tuberculosis therapy was promptly initiated, resulting in rapid clinical improvement and radiological resolution. CONCLUSIONS This case shows the limitations of conventional microbiological methods and unbiased mNGS in diagnosing extrapulmonary tuberculosis in immunocompromised patients. Capture-based targeted sequencing offers enhanced sensitivity for Mycobacterium tuberculosis detection and may facilitate timely diagnosis and appropriate treatment of spinal tuberculosis in patients undergoing MHD.