Pneumocystis Pneumonia in Thoracic Organ Transplantation: Current Perspectives and Updates

Pneumocystis jirovecii pneumonia (PCP) is an opportunistic infectious disease in thoracic solid organ transplant (SOT) recipients, occurring particularly in the setting of augmented immunosuppression. Thoracic allograft recipients are particularly at risk of severe outcomes. Diagnosis is frequently delayed due to nonspecific clinical findings and challenges in ruling out other opportunistic pathogens and distinguishing between pneumonia and colonization. Advances in molecular diagnostics, such as quantitative PCR (qPCR), droplet digital PCR (ddPCR), and loop-mediated isothermal amplification (LAMP), have considerably improved PCP diagnosis. Meanwhile, non-invasive diagnostic applications such as artificial intelligence (AI)-assisted imaging and radiomics hold promise for timely diagnosis. Trimethoprim-sulfamethoxazole (TMP-SMX) remains the first-line therapy; however, shorter treatment durations and lower-dose regimens have not been investigated to reduce toxicity. Alternative agents such as clindamycin-primaquine are used for documented intolerance. The effectiveness of adjunctive glucocorticoid therapy in post-transplant PCP remains unclear. Careful management of immunosuppression following a PCP diagnosis is essential to minimize the risk of allograft rejection. PCP prophylaxis remains a crucial component of the post-transplant preventive strategy, although further research is necessary to determine the optimal duration and dosing regimen. Future efforts should focus on developing risk stratification tools to implement tailored prevention strategies. Interventional studies are needed to provide evidence-based guidelines for PCP management and prevention. Continued advancements in diagnostics, therapeutics, and prophylaxis are vital to reducing the burden of PCP among thoracic SOT recipients.