A case of pleural Mycobacterium tuberculosis infection with reversion of Quantiferon Gold Plus results from positive to negative.

Introduction Mycobacterium tuberculosis continues to have a high mortality and morbidity burden globally. IGRA such as Quantiferon Gold Plus aid in diagnosis of latent TB but diagnosis of pleural TB remains challenging. We present a case of active pleural MTB infection with reversion of IGRA from positive to negative, and negative Xpert MTB/RIF Ultra PCR results from pleural biopsy tissues. Case A 52-year-old male presented in 2022 with a two-week history of pleuritic chest pain associated with modest elevation in inflammatory markers. The patient had had a positive QFG-Plus result in 2018, however QFG-Plus during this admission was negative. CTPA and needle thoracocentesis showed an exudative left pleural effusion with predominant lymphocytes. The patient’s symptoms failed to resolve with empiric antimicrobial therapy for community-acquired pneumonia. Broncho-Alveolar Lavage as well as biopsies of pleural tissues via video-assisted thoracoscopic surgery from the left lower lobe yielded negative results on routine microbiological culture as well as Xpert Ultra PCR. Growth of AFB was noted from mycobacterial cultures of pleural tissues which was identified as MTB. Conclusion Despite significant technological advances, microbiological diagnosis of MTB infections remains challenging. We document QFG-Plus reversion during development from latent to active pleural TB. Decline in the ability of CD4+ and CD8+ T cells to produce interferon gamma in response to TB antigens (ESAT-6 and CFP-10) was likely associated with loss of host control of latent MTB. This case serves as a reminder that despite exhaustive testing with state-of-art diagnostic platforms, MTB can still elude discovery.