Disseminated Bacillus Calmette-Guérin (BCG) infection presenting as severe respiratory failure and septic shock.

Introduction: Intravesical Bacillus Calmette-Guérin (BCG) instillation is the most effective adjuvant therapy for superficial urinary bladder carcinoma, prolonging disease-free survival. Although it is usually well tolerated, moderate to severe local or systemic infectious complications, including sepsis involving multiple organs, may occur.

Case report: We report the unusual case of a man in his mid '70s who presented with septic shock and severe acute respiratory failure requiring intubation. Lack of response to antibiotics, history of intravesical BCG instillation and consistent imaging findings led to further investigations, with bronchoalveolar lavage (BAL) fluid polymerase chain reaction (PCR) results indicating pneumonitis due to Mycobacterium bovis dissemination. Prompt anti-tuberculosis treatment combined with corticosteroids resulted in significant clinical and radiological improvement, supporting the diagnosis of disseminated BCG infection.

Conclusions: Due to its non-specific clinical presentation and the relatively low diagnostic yield of conventional microbiological tests, a high index of suspicion is required for prompt diagnosis and treatment of systemic BCG infection. PCR-based assays for mycobacterial DNA identification may represent a valuable tool facilitating timely diagnosis of this uncommon, yet potentially life-threatening infection.