Bacillus Calmette-Guerin (BCG) is a live attenuated strain of Mycobacterium bovis that is administered locally for treatment of superficial bladder cancer. It is usually well tolerated, but rarely, there can be infectious complications – both local and systemic.
The pathogenesis is not completely understood, but it is theorized that the organisms gain access to the lymphatics and blood via disrupted uroepithelium, with the potential to disseminate to multiple sites.
Severe adverse events due to instillation of BCG for bladder cancer are uncommon (less than 5%).
1) A mild cystitis develops in the majority of patients after instillation of BCG.
1) The most common severe systemic disease is a high fever (>39 degC), in ~3% of pts
2) Other systemic complications of BCG instillation include:
Pneumonitis (interstitial or military pattern)
The diagnosis of a BCG-related reaction can be difficult to confirm, as the mycobacteria are not always seen on acid-fast smears or cultures.
Here is a great CPC from NEJM on the infectious complications of BCG.