JC polyomavirus-associated nephropathy in a kidney transplant recipient

This report describes a man in his late 50s who underwent donation-after-circulatory-death kidney transplantation in 2012, due to end-stage kidney disease of unknown origin. More than a decade post-transplant, he presented with a progressive decline in graft function after maintenance immunosuppression had been reduced due to multiple skin carcinomas and the prolonged time since transplantation. Kidney biopsy revealed chronic-active tubulointerstitial nephritis with positive immunohistochemical staining for SV40, initially raising suspicion for BK polyomavirus-associated nephropathy. However, quantitative PCR (qPCR) analysis for BKPyV in both plasma and tissue was negative. In contrast, qPCR for JC polyomavirus (JCPyV) was positive in both plasma and biopsy tissue, leading to the diagnosis of JC polyomavirus nephropathy. Despite the reduction of immunosuppressive therapy, the patient experienced ongoing deterioration of graft function. Our report adds to the limited but growing body of literature on JCPyV and emphasises the need for increased clinical awareness and further research into its prevalence, pathogenesis and optimal management in kidney transplant recipients.