Spontaneous Resolution of Miliary Pulmonary Nodules Following Intravesical Bacillus Calmette-Guérin (BCG) Therapy: A Case Report and Literature Review.

Intravesical Bacillus Calmette-Guérin (BCG) immunotherapy is a well-established treatment for non-muscle-invasive bladder cancer. Although it is typically associated with local irritative symptoms, rare systemic and pulmonary complications can occur, including hypersensitivity pneumonitis and miliary tuberculosis. We report the case of a 70-year-old man who developed diffuse miliary pulmonary micronodules and ground-glass opacities after his 12th BCG instillation. Despite imaging findings suggestive of disseminated infection, the patient remained clinically stable, without fever, hypoxia, or systemic deterioration. Bronchoalveolar lavage cultures were negative for Mycobacterium bovis. A shared decision was made to withhold antimycobacterial therapy and monitor closely. Follow-up imaging revealed spontaneous improvement without treatment. This case underscores that observation may be appropriate in selected stable patients without systemic signs of infection. Careful clinical assessment and individualized management are essential to avoid unnecessary therapy and ensure patient safety.