A case of disseminated M. bovis bacillus Calmette-Guérin (BCG) disease after one month of BCG bladder infusion therapy and analysis of 77 cases of suspected BCG infection in Japan, 2017-2022.

Bacillus Calmette-Guerin (BCG) intravesical injections are used as adjuvant therapy for superficial bladder cancer. We report a case of a 78-year-old man who developed disseminated M. bovis BCG disease mimicking miliary tuberculosis early after BCG intravesical infusion. He started coughing after receiving three rounds of BCG for superficial bladder tumors, following transurethral resection of the tumors, approximately one month after initiation. Computerized tomography (CT) images showed diffuse nodular shadows in the bilateral lung fields with a random pattern. Consequently, disseminated BCG disease was diagnosed. Treatment with isoniazid, rifampicin, and ethambutol was initiated. Nine months after initiating treatment, CT showed the disappearance of the miliary shadows. We also discussed 77 cases of suspected BCG infection and the requests for Mycobacterium bovis BCG identification at our institution from 2017 to October 2022. Of these, 76 cases were M. bovis BCG, and 1 case was M. tuberculosis. Since M. tuberculosis can be identified in some patients with suspected BCG infection, it is crucial to distinguish between the two based on pathogenicity.