Pulmonary tuberculosis is usually diagnosed by microscopy and sputum smear culture, but diagnosis is difficult in patients with atypical imaging findings and negative conventional tests. The article describes the case of a 53-year-old immunocompetent woman with extensive bilateral opacities without classic symptoms of tuberculosis. Routine microbiological cultures, tests for acid-fast bacteria and serological tests were all negative. The diagnosis was established by next-generation metagenomic sequencing (mNGS) of bronchoalveolar lavage fluid, which identified Mycobacterium tuberculosis and was confirmed by a positive TB T-spot test. Standard antituberculosis treatment resulted in complete disappearance of opacities within nine months. The case highlights the importance of mNGS as an auxiliary diagnostic tool in cases where conventional methods fail, enabling early diagnosis and improved treatment outcomes.