Preemptive retransplant for BK virus nephropathy without concurrent transplant nephrectomy.

BK virus (BKV) nephropathy (BKVAN) has become an important cause of graft dysfunction after kidney transplant over the last decade (1). Consequently, consideration of retransplantation in the setting of BKVAN has become an increasingly pertinent issue. Questions of timing (preemptive vs. after progression to renal failure) and need for allograft nephrectomy remain unknown. Retransplantation has been reported in a total of 21 cases (2– 4), four of which were performed preemptively. All preemptive retransplants were performed with concurrent allograft nephrectomy because of concerns of possible BKV reinfection. We report for the first time a preemptive retransplant performed in a patient with BKVAN without simultaneous allograft nephrectomy. A 69-year-old woman had undergone living unrelated kidney transplant 5 years before presentation. Her first transplant was initially uneventful, but her baseline serum creatinine level increased during posttransplant months 8 to 14 from 1.3 to 4.0 mg/dL. A qualitative BKV blood polymerase chain reaction (PCR) was positive for BKV, and a biopsy demonstrated polyomavirusassociated interstitial nephritis with significant inflammation and fibrosis (retrospectively graded as b3 [5]). Five months after transition from tacrolimus/ mycophenolate/prednisone to low-dose sirolimus/leflunomide/prednisone, her viral PCR was undetectable, but she remained with a serum creatinine of 4.2 mg/dL (estimated glomerular filtration rate 12 mL/min). Leflunomide was discontinued, and she was placed on the transplant waiting list for retransplantation and maintained on sirolimus 2 mg daily (trough levels 4 – 8 ng/mL) and prednisone 5 mg daily with periodic monitoring of BKV. In the subsequent 4-year period, she remained clinically stable off of dialysis with an estimated glomerular filtration rate of 10 to 12 mL/min and BKV PCR that were undetectable, until she received a four-antigen mismatched deceased-donor kidney transplant. Three days before transplant, a screening BKV blood PCR had been undetectable. She received induction therapy with 1.5 mg/kg per day thymoglobulin for 3 days and was placed on tacrolimus, myfortic, and prednisone with immediate graft function. Figure 1 describes the clinical course of the patient. She experienced recurrent BKV viremia identified at 3 months posttransplant (after a steroid taper for gout) and underwent biopsy of both her first and second kidney transplants at posttransplant month 4 (BKV viremia 20,235 copies/mL). Neither kidney demonstrated SV40 staining for BKV despite examining two separate (totally four) cores including tissue at the corticomedullary junction from each kidney. Given the patchy distribution of BKV, the lack of findings may have reflected a sampling error or a potential uroepithelial source of BK viremia. Immunosuppression dose reduction resulted in a clearance of BKV viremia, and renal function remained stable throughout. This case is the first report of a successful preemptive kidney retransplant without graft nephrectomy in a patient with prior BKVAN. The clinical course highlights the need for ongoing monitoring of BKV replication both in the immediate posttransplant setting (to minimize the risk of development of BKVAN) and in the setting of the failing allograft (to dictate proper management and retransplant options). Critical to the decision making to not remove the failing allograft was the absence of BKV in blood at the time of retransplant. The success of our approach supports others’ FIGURE 1. Renal function and blood BK virus (BKV) polymerase chain reaction assessment after preemptive retransplant. Immunosuppression exposure is presented at monthly intervals. Despite stable renal function (serum creatinine [SCr] 0.8–0.9 mg/dL), the patient developed BK viremia prompting biopsy of both the failed allograft and functional second allograft. No BKV activity was identified in either biopsy by SV40 immunohistochemical staining. Decreased dosing of mycophenolate and tacrolimus resulted in clearance of BKV without clinical consequence.