Successful treatment of de novo thrombotic microangiopathy after minor ABO-mismatched living donor kidney transplantation.

We report a case of thrombotic microangiopathy developing after minor ABO-mismatched living donor kidney transplantation. The patient was a 57-yr-old woman whose blood group was B-positive. She received a kidney transplant from her husband whose blood group was O-positive. The recipient human leukocyte antigen haplotype was entirely different from that of the donor and the direct lymphocyte cross-match test was negative. The patient's hemoglobin and platelet (Plt) count fell rapidly from 11.0 g/dL and 34 x 104/[mu]L to 6.0 g/dL and 0.4 x 104/[mu]L between days 10 and 15 after kidney transplantation, with no evidence of bleeding. On day 8, anti-group B IgG and IgM antibodies were found in her serum. This anti-B antibody was thought to be produced from passenger B lymphocytes in the donor's kidney. Although in the case of hemolytic anemia after minor mismatched transplantation, the kidney function usually remains stable, the serum creatinine (s-Cr) rose from 0.8 to 5.2 mg/dL. On day 16, the helmet cells appeared in the serum and a total of 20 units of group O packed red blood cells and 30 units of group O Plts were transfused. Biopsy of the transplanted kidney was performed, which revealed thrombotic microangio-pathy, and appropriate therapy for DIC was administered, including anticoagulants, and cyclosporine A and mizoribine were replaced with tacrolimus and mycophenolate mofetil. Frequent plasma exchanges (PEX) with fresh frozen plasma were carried out. Furthermore, the anti-CD20 antibody rituximab was administered, because PEX had no effect. Following the adoption of these measures, the anti-donor antibodies disappeared to reduce the reaction on flow cytometric cross-match test; an anti-groupB antibody did not completely disappear but decreased in titer, and all the symptoms resolved immediately. The graft function recovered to a s-Cr level of 1.6 mg/dL by 34 d after the transplantation and she was discharged by 36 d after the transplantation. At present, she is entirely healthy and the graft function remains good with a s-Cr level of 1.1 mg/dL., Copyright (C) 2008 Blackwell Publishing Ltd.