American Board of Internal Medicine (ABIM) Certification Practice Exam

Which infection risk significantly increases with the need for increased immunosuppression following a transplantation?

1. Viral respiratory infections

2. Pneumocystis jirovecii infection

3. Urinary tract infections

4. Fungal skin infections

The correct answer is: Pneumocystis jirovecii infection

The significant increase in the risk of Pneumocystis jirovecii infection following transplantation is closely related to the immunosuppression required to prevent organ rejection. This protozoan parasite commonly causes pneumonia in individuals with weakened immune systems, particularly those undergoing immunosuppressive therapy after an organ transplant. In transplantation, the immune system is intentionally suppressed to prevent the body from rejecting the new organ, and this increased immunosuppression directly affects the body's ability to fight off infections. Pneumocystis jirovecii is particularly notable because it is an opportunistic pathogen; under normal circumstances, it might not cause any harm, but in an immunocompromised host, especially those with CD4 T-cell counts significantly reduced, it can lead to severe pneumonia. While other infections such as viral respiratory infections, urinary tract infections, and fungal skin infections can also occur in transplant patients due to immunosuppression, Pneumocystis jirovecii pneumonia remains a classic and critical concern due to the specific immune mechanisms involved in its pathogenesis and the high morbidity and mortality associated with this infection in transplant recipients. Prophylactic measures against Pneumocystis jirovecii are often instituted in transplant patients to mitigate this risk.