[BK virus nephropathy in a kidney transplant recipient: a case report and literature review]

BK virus nephropathy (BKVN) has emerged as an important cause of allograft dysfunction and loss in kidney transplant recipients. We present a case in a 30-year-old female who underwent ABO-compatible living kidney transplant from her mother and was maintained with tacrolimus, mycophenolate mofetil and prednisolone. The serum creatinine level was stabilized about 0.9 mg/dl on postoperative day (POD) 35. On POD258, the serum creatinine increased to 1.8 mg/dl and the patient received methylpredonisolone pulse therapy under the diagnosis of acute rejection, which resulted in further increase in creatinine level from 1.8 to 2.6 mg/dl. Urine cytology showed decoy cells, but renal biopsy specimen showed no evidence of viral infection. Despite histopathological findings, positive urine and serum BKV-DNA suggested that allograft dysfunction was caused by BKVN. Therefore, the immunosuppession was reduced and gamma-globuline was given for 2 weeks. After the treatment, urine cytology became negative for decoy cells and serum creatinine level recovered to 2.0 mg/dl. On POD456, serum creatinine level was stabilized about 1.8 mg/dl and decoy cells remained negative.