A case of polyomavirus-associated nephropathy presenting late after transplantation

Background: A 36-year-old white female, who had received a deceased-donor kidney transplant for end-stage renal disease secondary to reflux nephropathy 8 years previously, was referred to a transplant clinic for evaluation following an increase in her serum creatinine level from 123.8 μmol/l to 185.6 μmol/l (1.4 mg/dl to 2.1 mg/dl) over the preceding 9 months. Her immunosuppression regimen included mycophenolate mofetil, ciclosporin and prednisone, with ciclosporin trough levels ranging from 100 ng/ml to 150 ng/ml, as detected by fluorescence polarization immunoassay, over the preceding year. The following possible causes of subacute renal failure were ruled out: post-obstructive nephropathy, altered hemodynamics (hypotension and renal artery stenosis), and toxicity from medications other than calcineurin inhibitors. Potential etiologies such as acute T-cell-mediated rejection, acute and chronic antibody-mediated rejection, polyomavirus-associated nephropathy, and calcineurin inhibitor nephrotoxicity were considered. Investigations: Physical examination, urine and blood analysis, analysis of human leukocyte antigen antibodies by flow cytometry (Luminex®, Luminex Corporation, Austin, TX), ultrasound of the transplanted kidney, polymerase chain reaction assay for the detection of BK virus in the serum, and biopsy of the transplanted kidney with staining for simian virus 40 antigen. Diagnosis: Polyomavirus-associated nephropathy with advanced nephrosclerosis and moderate to marked hyaline arteriolosclerosis. Management: Reduction of immunosuppression by discontinuation of mycophenolate mofetil, dose reduction of ciclosporin, and initiation of leflunomide.