INTRODUCTION: Late AMR can develop at any time post kidney transplantation and represents a major challenge.

OBJECTIVE: To characterize a series of kidney transplant recipients with late AMR and the response to treatment.

METHODS

This is a retrospective case series of kidney transplant patients who were diagnosed with a late antibody-mediated rejection (AMR).

RESULTS: 31 kidney transplant recipients with late (> 90 days after transplantation) antibody-mediated rejection could be identified. Patient age at transplantation was 39.5±18.3 years (donor age 48.4±15.4 years). 13/31 patients received a transplant from a living donor. 9/31 received a 2nd or 3rd transplant. ABDR mismatch was 3.8±1.4. Only two patients had a PRA of >25% at time of transplantation. All patients had a negative CDC crossmatch at time of transplant. Two patients had donor-specific antibodies (both received desensitization therapy before or shortly after the transplant), one of these two patients had a positive flow cytometry crossmatch at transplantation. Antibody-mediated rejection was detected at a mean time of 63.7±77.0 (2.3-249) months after transplantation. In all but one patient AMR was detected by indication biopsy, in one patient by one-year protocol biopsy. 9/31 patients received a triple therapy containing Tacrolimus (> 3 ng/mL), MMF of ≥ 1g/day, and prednisone ≥ 5 mg/day. 4 patients received a CNI-free mTOR-I-based therapy, another 4 patients a combination of CNI and mTOR-I. 13 patients had a steroid free (or very low dose steroid therapy; ≤ 7.5 mg/week). The mean lowest post-transplant serum creatinine was 1.2±0.3 mg/dL. At time of rejection 2.34±1.06 mg/dL (Proteinuria 1599±2376). All but three patients received treatment with rituximab, IVIG, PE. Time of follow up was 23.5±11.1 months (1.6-54.9) months. 9/31 (29%) grafts were lost at 9.5±8.7 months after diagnosis of AMR (1.2-28 months). Cr at last follow-up of the remaining 22 patients was 2.5±1.35 mg/dL (Proteinuria 1178±1582 mg/day). Response to treatment in terms improvement of Cr and Proteinuria was associated with better graft survival. Reduction of DSA was not associated with better outcomes.

CONCLUSION:

Late AMR is associated with a high rate of graft loss within two years in spite of treatment with rituximab, IVIG, PE and reduction of the DSA concentration.

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