BCG gone rogue: A case report of disseminated Mycobacterium bovis

Bacillus Calmette-Guérin (BCG) bladder instillation is an effective therapy for non-muscle-invasive bladder cancer. Disseminated Mycobacterium bovis infection is a rare but potentially life-threatening complication. Despite increasing use of intravesical BCG, evidence-based guidance regarding its administration in immunocompromised patients remains limited. Here, we report a case of disseminated M. bovis infection presenting as fever of unknown origin.

A 59-year-old man presented to the hospital with fevers and chills. His past medical history was significant for renal transplantation with subsequent graft failure. He was maintained on tacrolimus 3 mg twice daily and prednisone 10 mg daily. He also had a history of bladder cancer treated with intravesical BCG immunotherapy 2 years prior to presentation. His hospital course was complicated by persistent undulating fevers. Computed tomography of the chest revealed a small cavitary lesion in the right upper lobe, and positron emission tomography imaging demonstrated increased uptake in the right iliopsoas muscle. A QuantiFERON Gold tuberculosis test was positive. Thirty days after presentation, acid-fast bacillus (AFB) blood cultures obtained at initial presentation, as well as AFB cultures from bronchoalveolar lavage and iliopsoas aspirate, grew pyrazinamide-resistant Mycobacterium tuberculosis complex. Subsequent sequencing identified M. bovis, consistent with disseminated infection related to prior intravesical BCG therapy.

This case of fever of unknown origin was ultimately attributed to disseminated M. bovis infection, likely related to prior intravesical BCG therapy in an immunocompromised patient. Early recognition of this rare complication is critical, as disseminated M. bovis infection may present with severe systemic illness and multi-organ involvement.