Low prevalence of BK virus nephropathy on nonprotocol renal biopsies in Iranian kidney transplant recipients: one center's experience and review of the literature.

OBJECTIVES: BK virus-associated nephropathy in renal transplant recipients has been increasing in frequency in recent years. This rise is probably because of widespread use of highly potent immunosuppressive regimens, and increased immunosuppression load leads to inability of the recipients to increase a successful antiviral immune response. The incidence of BK virus-associated nephropathy in different reports is between 1% and 10%, with an allograft loss in significant numbers of patients, especially when timely diagnosis and treatment is not restored. We report our experience on BK virus nephropathy in our institute. MATERIALS AND METHODS: All renal transplant biopsies performed at our center between 2001 and 2006 were immunohistochemically screened for the presence of PV-specific protein (SV40 Ag). The histologic diagnosis of BK virus-associated nephropathy was made upon the observation of morphologic changes in tubular epithelium and confirmation with immunohistochemical staining. We reviewed the clinical records of the subjects for demographic, clinical, and laboratory data. RESULTS: BK virus nephropathy was found in 0.93% of all investigated allograft biopsies (1/108) and in 1.04% of all recipients (1/96; mean age of recipients, 36.48±14.10 years; age range, 13-74 years); 54 of them were male (57%). Type of kidney transplant was living-unrelated donor 76 (79%), living-related donor 13 (14%), and deceased donor 7. Seventeen patients (18%) were transplanted for a second time. Immunosuppressive drugs in 87 of recipients (90%) were cyclosporine, mycophenolate mofetil, and prednisolone. Our patient who developed BK virus-associated nephropathy 9 months after transplant was a 37-year-old man on prednisone, cyclosporine, and azathioprine immunosuppresion. He lost his graft 4 months after diagnosis. CONCLUSIONS: Although BK virus nephropathy after renal transplant is uncommon, it is a serious complication causing loss of the allograft. It should be included in the clinical differential diagnosis of transplant dysfunction.