Culture-Confirmed Multilobar Cavitary Pulmonary Tuberculosis Despite a Negative QuantiFERON-TB Gold Assay in an Immunocompetent Young Adult.

Pulmonary tuberculosis (TB) remains a major global health concern and may present with radiographic and laboratory findings that complicate timely diagnosis. Interferon-gamma release assays (IGRAs), including QuantiFERON-TB Gold, are blood tests that measure T-cell immune sensitization to Mycobacterium tuberculosis antigens; they do not distinguish latent infection from active disease and cannot exclude active TB. We report a 23-year-old immunocompetent Venezuelan-born man who presented with fever, night sweats, productive cough, and intermittent hemoptysis after approximately seven months of respiratory symptoms. Chest imaging demonstrated multilobar cavitary disease involving both upper lobes and the left lower lobe. Despite a negative QuantiFERON-TB Gold result, two sputum acid-fast bacilli smears were positive, M. tuberculosis nucleic acid amplification testing was positive, and mycobacterial culture confirmed the M. tuberculosis complex. The patient was placed in airborne isolation and treated with rifampin, isoniazid, pyrazinamide, and ethambutol. Public health authorities coordinated directly observed therapy, contact investigation, and outpatient sputum monitoring. This case demonstrates that a negative IGRA cannot rule out active pulmonary TB and that atypical multilobar cavitation should not lower clinical suspicion when epidemiologic, clinical, and microbiologic findings support the diagnosis.