B71-03 Culture-negative Disseminated Tuberculosis Mimicking Autoimmune and Malignant Disease

Abstract Background Disseminated Mycobacterium tuberculosis (TB) can present insidiously and mimic autoimmune or malignant disease when microbiologic studies are negative. Repeated negative acid-fast stains and nondiagnostic biopsies may obscure diagnosis, leading to progressive multiorgan involvement. This case highlights the diagnostic complexity of culture-negative disseminated TB in a critically ill patient with initially misleading findings. Case Report A 44-year-old woman with bipolar disorder and hypothyroidism was admitted with dyspnea, weight loss, and weakness. One month earlier, she had been hospitalized for presumed community-acquired pneumonia. Imaging had shown a left pleural effusion and multiple soft-tissue masses concerning for malignancy, but she declined further work-up. On readmission, CT revealed diffuse mediastinal, abdominal, and pelvic lymphadenopathy, pleural-based and chest-wall masses, and ascites. Two thoracenteses produced exudative fluid without malignant cells. Acid-fast bacilli (AFB) stains and cultures from pleura and ascites were repeatedly negative. Core needle biopsies of the chest-wall mass twice showed necrotizing granulomatous inflammation without acid-fast or fungal organisms; bone-marrow biopsy was unremarkable. Laboratory testing demonstrated positive ANA and anti-RNP antibodies, low complement, and elevated rheumatoid factor, suggesting autoimmune disease. A QuantiFERON-TB Gold assay was positive, but three sputum AFB smears and cultures were negative. Despite extensive evaluation, no definitive diagnosis was reached, and the patient deteriorated with recurrent effusions and systemic inflammation. Excisional biopsy of a supraclavicular lymph node ultimately revealed necrotizing granulomatous inflammation, and broad-range PCR detected M. tuberculosis DNA. Antituberculous therapy with rifampin, isoniazid, pyrazinamide, and ethambutol with pyridoxine was initiated, confirming disseminated TB. Discussion This case illustrates the diagnostic challenge of disseminated TB in low-prevalence settings where malignancy or autoimmune disease may be suspected first. Negative cultures occur in up to 50% of extrapulmonary or disseminated TB cases, and necrotizing granulomas are not pathognomonic, often mimicking sarcoidosis or vasculitis 1, 2. Molecular assays such as PCR or nucleic-acid amplification testing (NAAT) detect M. tuberculosis with greater sensitivity and should be used early when conventional studies are inconclusive 3. Clinicians should maintain suspicion for TB in patients with unexplained exudative effusions or granulomatous inflammation and employ molecular diagnostics promptly to prevent progression to critical illness. References 1. Sharma SK, Mohan A. Extrapulmonary tuberculosis. Indian J Med Res.2021;153(4):448-471. 2. Bruchfeld J, et al. Molecular tools in the diagnosis of extrapulmonary tuberculosis: a systematic review and meta-analysis. Eur Respir J. 2021;57(3):2002049. 3. Dheda K, Barry CE, Maartens G. Tuberculosis. Lancet. 2016;387(10024):1211-1226. This abstract is funded by: None