Biopsy-proven BK virus nephropathy in renal transplant recipients: A multi-central study from Turkey (BK-TURK STUDY).

Aim: BK polyomavirus infection is a challenging complication of renal transplantation. The management is not standardized and is based on reports from transplantation centers' experiences, usually with small sample sizes. Therefore, we aimed to present our countrywide experience with BK virus nephropathy (BKVN) in renal transplant recipients.

Materials and methods: Our study was carried out with the participation of 30 transplantation centers from all regions of Turkey. Only cases with allograft biopsy-proven BKVN were included in the study.

Results: 13,857 patients from 30 transplantation centers were screened, and 207 BK nephropathy cases were included. The mean age was 46.4 ±  13.1 years, and 146 (70.5%) patients were male. The mean time to diagnosis of BK nephropathy was 15.8 ± 22.2 months after transplantation. At diagnosis, the mean creatinine level was 1.8 ±  0.7 mg/dL, and the mean estimated glomerular filtration rate was 45.8 ± 19.6 mL/min/1.73m². In addition to dose reduction or discontinuation of immunosuppressive drugs, 18 patients were treated with cidofovir, 11 patients with leflunomide, 17 patients with quinolones, 15 patients with intravenous immunoglobulin (IVIG), 5 patients with cidofovir plus IVIG, and 12 patients with leflunomide plus IVIG. None of the patients receiving leflunomide or leflunomide plus IVIG had allograft loss. During follow-up, allograft loss occurred in 32 (15%) out of 207 patients with BK nephropathy.

Conclusion: BKVN is still a frequent cause of allograft loss in kidney transplantation and is not fully elucidated. The results of our study suggest that leflunomide treatment is associated with more favorable allograft outcomes.