Infection of the acromioclavicular joint with Mycobacterium bovis following intravesical instillation of Bacillus Calmette-Guerin: a case-based review

Purpose Osteoarticular infections caused by intravesical BCG are rare and poorly characterized. This study presents a case of acromioclavicular joint infection caused by Mycobacterium bovis BCG, alongside a systematic review aimed at improving our understanding of the infection's clinical features, diagnosis, treatment and outcomes. Methods This systematic review included all published cases of osteoarticular infections due to M. bovis BCG following intravesical BCG instillation, as identified through a PubMed search conducted up to 1 May 2025. The search used combinations of keywords related to 'BCG', 'bladder', and 'osteoarticular infection'. One additional case from our institution was added. Clinical, biological, radiological, treatment and outcome data were extracted and analyzed. Results We reviewed 67 cases, classified as vertebral (n = 45), prosthetic joint (n = 18), and native joint (n = 4). The affected patients were predominantly men (98.5%), with a mean age of 74.1 ± 9.2 years. The median delay in months between the first instillation and the diagnosis was 23 [IQR 13.0-48.0]. Fever was uncommon (20.5%), while elevated C-reactive protein levels were frequent (80%). Imaging (CT/MRI) played a key role in diagnosis by showing images consistent with infection in all cases in which it was used. Treatment typically involved rifampicin and isoniazid for 12 months, alongside ethambutol for two months. Outcomes were favorable in 90.6% of cases, with one death attributed to the infection. Conclusion Though rare, M. bovis BCG osteoarticular infections should be considered in patients with unexplained joint symptoms following BCG therapy. Early diagnosis and appropriate therapy are essential for optimal management.