BK virus viremia in a well-HLA-matched kidney transplant population mainly on low-dose cyclosporine-based immunosuppression.

The incidence and clinical course of polyomavirus-associated nephropathy (PyVAN) in our well-HLA-matched kidney transplant population mainly on low-dose cyclosporine-based triple-drug immunosuppression has not been described in detail. We aimed to characterize our patients with PyVAN and BK virus (BKV) viremia. Among 166 kidney transplantations between January 2007 and February 2011 followed up at Helsinki University Hospital nephrology clinic, 136 were screened for BKV viremia by quantitative analysis of BKV DNA in plasma. PyVAN was diagnosed by biopsy histopathology and SV40 T-antigen detection. BKV viremia or PyVAN were treated by reducing immunosuppression. BKV viremia was detected in 12 (9%) patients. PyVAN was diagnosed in six patients (4%). In the six patients with no PyVAN, four had low-level viremia (<10,000 copies/mL) of short duration (<2 months), one had high-level viremia, and one had sustained low-level viremia. After reduction of immunosuppression, all except one patient were able to clear viremia. No grafts were lost due to PyVAN. Even in a low-risk population, BKV viremia and PyVAN occur, highlighting the importance of monitoring viral loads. Reduction of immunosuppression was successful, and no grafts were lost due to PyVAN.