BK nephropathy in kidney transplant recipients treated with a calcineurin inhibitor-free immunosuppression regimen.

Recently, polyomavirus-associated nephropathy (PVAN) has been reported more frequently and is emerging as an important cause of renal allograft dysfunction and graft loss. Susceptibility appears to be related to the type and intensity of pharmacologic immunosuppression but some reports have suggested a link among the development of PVAN, the treatment of rejection or maintenance with a tacrolimus-based immunosuppressive regimen. We report three cases of PVAN in patients who never received immunosuppression with calcineurin inhibitors (CNIs). Two patients received induction immunosuppression consisting of an IL-2 receptor antagonist while 1 received thymoglobulin. These 3 patients were maintained on prednisone, sirolimus and mycophenolate mofetil (MMF) and none was treated for rejection. All three patients presented with an elevated serum creatinine and demonstrated polyomavirus infection on biopsy and by blood PCR. These cases demonstrate that, unlike reports linking tacrolimus and PVAN, polyomavirus infection may develop in patients maintained on CNI-free immunosuppressive regimens and have not had episodes of rejection.