Timing and Clinical Impact of Opportunistic Infections in Pediatric Kidney Transplant Recipients: A 10-Year Single-Center Experience

Background/Objectives: Opportunistic infections remain clinically important after kidney transplantation and may contribute to morbidity and graft dysfunction in pediatric recipients. Data regarding their timing, spectrum and clinical course in children remain limited. Methods: We retrospectively reviewed pediatric kidney transplant recipients followed at a single tertiary center between 2014 and 2024. Demographic and clinical characteristics, infection type, timing after transplantation, management and outcomes were recorded. Infection incidence was assessed at the patient level, whereas pathogen distribution and timing were analyzed per infection episode. Results: Twenty-seven pediatric kidney transplant recipients were included, with a mean follow-up of 5.6 years. Ten patients (37.0%) developed at least one clinically significant opportunistic infection, and one patient experienced two distinct episodes, resulting in 11 infection events. BK virus was the most frequent pathogen, followed by fungal infections and cytomegalovirus (CMV). Five episodes (45.5%) occurred within the first post-transplant year, whereas six (54.5%) occurred later during follow-up. Late infections included CMV, fungal infections, BK virus and West Nile virus. Most infections resolved after targeted management without persistent graft impairment; however, one patient developed biopsy-confirmed BK virus-associated nephropathy with sustained graft dysfunction. No infection-related mortality was observed. Conclusions: Clinically significant opportunistic infections occurred both early and late after pediatric kidney transplantation, with more than half of all infectious episodes developing beyond the first post-transplant year. Although overall outcomes were favorable, BK virus-associated nephropathy remained clinically relevant because of its impact on graft function.