Intravesical Bacillus Calmette-Guérin (BCG) Immunotherapy-Related Pneumonitis: A Case Report.

Intravesical bacillus Calmette-Guérin (BCG) immunotherapy is widely used as a standard adjuvant treatment for non-muscle invasive bladder cancer. The exact mechanism of BCG action and the mechanisms responsible for early and late complications after intravesical BCG treatment remain poorly understood, and it is still unclear in which patients local or systemic adverse effects will develop. The patient who received intravesical BCG treatment for six weeks presented with complaints of arthralgia, loss of appetite, fatigue, and intermittent low-grade fever. High-resolution chest computed tomography showed bilateral ground-glass opacities and showed no response to antiviral or antimicrobial treatments. Bronchoalveolar lavage flow cytometry demonstrated a markedly elevated CD4/CD8 ratio (6:1). Based on clinical, radiologic, and immunologic findings, pneumonitis secondary to BCG-related inflammation (BCG-itis) was diagnosed. Differentiating infectious from immune-mediated adverse events in BCG-itis can be challenging.