BK Nephropathy in the Modern Era: What Have We Learned?

BK polyomavirus (BKPyV) remains a significant cause of graft dysfunction and failure in kidney transplant recipients, with DNAemia affecting up to 30% and nephropathy contributing to approximately 7% of graft losses. This review synthesizes current understanding of BKPyV pathogenesis, risk factors, and management strategies. Screening protocols and immunosuppression reduction remain the cornerstone of care, though emerging therapies-including monoclonal antibodies and virus-specific T-cell therapies-offer promise. The role of mTOR inhibitors and other agents is critically evaluated, with recent trials challenging their efficacy. Unique transplant-related factors, such as ureteral stent use and the kidney's role as a viral reservoir, may explain the predominance of BKPyV in renal transplantation. The review highlights the need for improved serologic and cellular immunity assays, targeted antiviral therapies, and individualized approaches to retransplantation. Continued research is essential to reduce the burden of BKPyV-associated nephropathy and improve long-term kidney transplant outcomes.