Persistently High-Level Polyomavirus BK Replication in the Absence of Renal Function Abnormalities in a Kidney Transplant Recipient

Polyomavirus-associated nephropathy is an important cause of allograft dysfunction and graft loss after kidney transplantation. Even if histological evaluation is the gold standard for graft study and diagnosis of polyomavirus-associated nephropathy, K-DIGO guidelines suggest performing an indication biopsy in selected patient’s clinical conditions or laboratory parameters. The practice of protocol biopsy is still controversial. We report the management of a case of presumptive polyomavirus-associated nephropathy in a 53-year-old kidney transplant recipient affected by type 1 hyperoxaluria with persistent high levels of viruria and sustained levels of polyomavirus BK viremia. The presence of a presumptive polyomavirus-associated nephropathy, even if never confirmed by biopsy, never compromised his clinical condition and allograft function. As a result of an immunosuppression-sparing policy and use of mTOR inhibitor, the polyomavirus BK viremia was successfully controlled with an observation time >5 years. The decision to perform or not a graft biopsy was the main question in the management of this case. We opted for a non-invasive approach because of the high risk of biopsy with macrohematuria on earlier biopsy in a dual kidney transplant and patient’s unwillingness for the procedure. The replication level of polyomavirus BK was significantly reduced by the decrease of immunosuppression on the basis of a close nucleic acid testing monitoring. The strategy we adopted could be considered in cases when renal biopsy is contraindicated or considered to be high risk.