BK polyomavirus nephropathy complicated with acute T-cell-mediated rejection in a kidney transplant recipient: a case report.

We present a case of severe BK polyomavirus nephropathy (BKVN) complicated with persistent acute T-cell-mediated rejection (ATMR) that progressed to allograft failure. A 54-yr-old man received a living donor kidney transplant from his wife. Approximately four months after transplantation, the patient's serum creatinine (SCr) increased from a baseline value of 1.5-2.4 mg/dL. A histological analysis showed BKVN, and the SV40 antigen was detected in the tubular nuclei. The doses of immunosuppressants were reduced, and immunoglobulin was administered intravenously. The SCr increased further, to 5.3 mg/dL, and a second renal biopsy revealed the presence of severe ATMR. Antirejection treatment was performed, and low-dose cidofovir was started. The SCr decreased, to 3 mg/dL, and BK virus antigen in the serum and urine samples became negative at the time of hospital discharge. However, the histological findings subsequently showed gradually progressive interstitial fibrosis and tubular atrophy, and the SCr increased gradually. Two years after the transplantation, the patient resumed hemodialysis. BK polyomavirus nephropathy is usually treated with a reduction in immunosuppressant therapy, although in some patients, the reduction in immunosuppressants induces a subsequent exacerbation of acute rejection and results in progressive graft failure, which suggests difficulty in treating BKVN after kidney transplantation.