BCGitis and BCGosis spectrum of imaging findings in immunocompromised pediatric patients.

Tuberculosis (TB) remains a significant public health concern despite preventive measures, such as the use of the Bacille Calmette-Guérin (BCG) vaccine, which reduces the risk and severity of early-life TB infection. The adverse effects of the BCG vaccine include infection by the live-attenuated organism, more commonly seen in the immunocompromised host. This pictorial review aims to outline the imaging spectrum of BCG-vaccine-related infections in immunocompromised pediatric patients, which can be localized (BCGitis) or disseminated (BCGosis). We illustrate the more common imaging findings, including lymphadenopathy and involvement of solid organs, as well as less frequently encountered sites, such as the lungs and gastrointestinal tract, emphasizing their distinct imaging patterns. Interpretation of these findings in the context of prior administration of the BCG vaccine not only helps in the diagnosis of BCG-vaccine-related infections and guiding timely management, but can also be an early indicator of an underlying immunodeficiency disorder, prompting comprehensive immunological investigation.