Severe osteoarticular and skin and soft tissue infection with Mycobacterium bovis following intravesical BCG instillation

•Intravescial BCG for bladder cancer is generally considered safe, although rare systemic complications have been described.•When local or systemic symptoms appear after BCG treatment, early recognition of complications is essential.•Treatment should include a systemic antimycobacterial regimen, excluding pyrazinamide due to intrinsic resistance in M. Bovis.•Consideration of surgical interventions may be warranted for extended (prosthetic) joint infections to achieve source control.•Consider paradoxical reactions when symptoms recur during and after discontinuation of immunosuppressive therapy. We describe the case of a 70-year-old immunocompromised patient who developed a severe disseminated Mycobacterium bovis BCG infection with several infected prosthetic joints and soft tissue abscesses following intravesical BCG instillation for bladder cancer. This case report addresses the risk of severe complications in immunocompromised patients and the challenges in the management of this potentially life-threatening condition.