A70-13 Disseminated Tuberculosis Presenting as a Necrotic Mediastinal Mass With Vertebral Involvement (Pott’s Disease) and Psoas Abscess in a 33-Year-Old Male

Abstract Mycobacterium tuberculosis (Mtb) can disseminate via hematogenous or lymphohematogenous routes. Disseminated Mtb, a severe form of the disease, is defined as involvement of at least two non-contiguous sites. Disseminated Mtb can mimic malignancy or infection and may yield false negative interferon-gamma release assay (IGRA) posing a diagnostic challenge, leading to therapeutic delays. We describe a previously healthy 33-year-old incarcerated man with three months of fatigue, fevers, night sweats, 30-pound weight loss, dyspnea, pleuritic chest pain, and progressive leg weakness. He appeared chronically ill, febrile, and tachycardic, with decreased right-sided breath sounds. Labs revealed normocytic anemia, thrombocytosis, markedly elevated ESR and CRP, mild transaminitis, hypoalbuminemia, and negative HIV serology. Despite strong clinical suspicion, both QuantiFERON-TB Gold Plus and serial sputum AFB smears were negative. CT imaging revealed a large necrotic posterior mediastinal mass with coarse calcifications, T4-T7 vertebral erosions, T5-T6 pathologic fractures, and epidural extension causing canal compromise. Additional findings included a right pleural effusion, lytic fourth-rib lesion, bilateral sacroiliitis, and a ring-enhancing right iliopsoas abscess.Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) of a retrotracheal (3P) node produced necrotic purulent material. Bronchoalveolar lavage was AFB-positive, and nucleic-acid amplification testing confirmed Mtb complex. Drug-susceptibility testing demonstrated a fully susceptible strain. Standard RIPE (rifampin, isoniazid, pyrazinamide, ethambutol) therapy with pyridoxine was initiated, and a 12-month course was planned due to extensive osseous involvement. Neurosurgery recommended conservative management given the absence of neurologic deficits despite epidural compression. Early follow-up imaging showed paradoxical worsening, likely from immune reconstitution, while clinical status and inflammatory markers improved with therapy. Mtb presenting as a large necrotic mediastinal mass often mimics malignancy, particularly lymphoma or metastatic carcinoma, creating major diagnostic challenges. The presence of necrotic mediastinal adenopathy, anterior vertebral body destruction with disc preservation, and large paravertebral and psoas abscesses strongly suggested Mtb. Cases of Mtb with a similar presentation of mediastinal mass, Pott’s disease, and psoas abscess have been documented in the literature, further increasing our suspicion. EBUS-TBNA provided minimally invasive diagnostic confirmation through necrotizing granulomas and PCR identification of Mtb, while CT-guided aspiration of a rib lesion was AFB- and Mtb DNA-positive by NAAT. EBUS-TBNA demonstrates high diagnostic accuracy (79-91% overall; 62-100% for Mtb), supporting its use over more invasive procedures. The negative QuantiFERON-TB Gold result highlights limitations of IGRAs in severe or disseminated Mtb. Multidisciplinary management and an extended 12-month ATT regimen were essential to achieve cure and prevent relapse, emphasizing the need for multimodal management. This abstract is funded by: None