Polyomavirus associated nephropathy presenting five years after kidney transplantation.

Background: Polyomavirus associated nephropathy (PVAN) is being recognised as an important cause of renal transplant dysfunction. It is a difficult diagnosis to make and requires a high index of suspicion. Here we describe an unusually late presentation of PVAN that responded favourably to reduction of immunosuppression.

Methods: A 52 year-old male presented with an elevated serum creatinine of 3.8 mg/dl five years after kidney transplantation. He was maintained on tacrolimus, mycophenolate mofetil (MMF), and prednisolone. He had loose motions that subsided when MMF was withdrawn. His tacrolimus trough level was very high and its dose was reduced, with no improvement in creatinine level. Doppler of the transplanted kidney revealed normal perfusion. The patient's urine was negative for decoy cells and his plasma PCR for polyoma BK virus DNA was also negative. Kidney biopsy revealed histological features suggestive of PVAN and this diagnosis was confirmed by immunohistochemistry which was positive for simian virus 40 (SV40) antigen. Tacrolimus was discontinued and the patient maintained on azathioprine and prednisolone. His serum creatinine stabilized at 1.2 mg/dl.

Conclusions: This case highlights the propensity of PVAN to present very late after transplantation. Renal biopsy is very valuable in establishing the diagnosis and timely management can prevent graft loss.