Objective  To explore the clinical application experience of leflunomide in rescuing therapy of BK virus nephropathy (BKVN) after renal transplantation in the case of ineffective treatment with reduction of immunosuppressant.

  Methods  Four recipients with BKVN after renal transplantation were diagnosed at 135^th-737^th day after operation, with the pathological staging as following: 2 cases in stage A1, 1 case in stage B1 and 1 case in stage B2. For all recipients, leflunomide was used for rescuing therapy due to ineffective treatment with reduction of immunosuppressant for 0.5-3.0 months. Initially, 50 mg/d of leflunomide was given continuously for 3 days, so as to reach therapeutic serum concentration, and then 20 mg/d of leflunomide was given for maintaining. The efficacy and safety were observed.

  Results  After a follow-up for an average of 6 months (5-7 months), 3 recipients with development of BKVN were controlled effectively, 1 recipient (stage B2) with ineffective treatment. No obvious adverse reactions occurred during medication.

  Conclusions  It is possible to slow down the development of BKVN and reduce the incidence of renal allograft loss by using leflunomide to conduct rescuing therapy of BKVN after renal transplantation in the case of ineffective treatment with reduction of immunosuppressant. Better effect can be achieved if early detection and diagnosis of BKVN are conducted as well as effective measures are taken timely in the early pathological stage.