Subclinical miliary Mycobacterium bovis following BCG immunotherapy for transitional cell carcinoma of the bladder

The authors present an unusual case of a 51-year-old man who developed relatively mild non-specific symptoms following intravesical BCG instillation for superficial transitional cell carcinoma of the bladder, with radiological investigations demonstrating typical features of miliary tuberculosis (TB). Transbronchial biopsy showed small foci of poorly formed granuloma suggestive of Mycobacterium infection. The patient's respiratory symptoms only became apparent 7 days after discharge having had 4 weeks of unremarkable inpatient stay where he remained clinically well. Prompt anti-TB treatment resulted in a remarkable improvement in his symptoms and radiological appearance, supporting the diagnosis of disseminated Mycobacterium bovis infection. This case highlights the importance of recognising miliary M bovis as a potential complication in patients receiving BCG immunotherapy, and that the disease course can be subclinical with delayed onset of symptoms.