Thrombotic microangiopathy (TMA) in the renal allograft is a form of renal capillary injury that may associate with many disorders including calcineurin inhibitor (CI) toxicity, antibody-mediated rejection (AMR), infections, and recurrent diseases. In this study, we aimed to show the incidence of thrombotic microangiopathy in patients with the diagnosis of acute humoral rejection (AHR), chronic active humoral rejection (CAHR), polyomavirus nephropathy (PVN), acute cellular rejection (ACR) and IgA recurrence.

All patients who had diagnosed as PVN and IgA recurrence between 2006 and 2016 included into the study and reevaluated for the final diagnosis and presence of TMA. Consecutive renal allograft biopsies diagnosed as AHR, ACR, and CAHR within 24 months also evaluated for the final diagnosis, presence of C4d expression and TMA. The positive C4d expression criteria reconsidered according to the latest Banff criteria and the final diagnosis given in all cases. Clinical data and the immunosuppressive (IS) therapy reviewed and noted for all cases.

Total 272 patients with a mean age of 42,8±12,7 years studied. Of 272 patients 90 patients had AHR, 51 had ACR, 55 had PVN, 53 had CAHR and 23 had IgA nephropathy. Among these 272 patients, only 74 patients (27.2%) had TMA. TMA found in 30 of 90 (33.3%) AHR, 9 of 51 (17,6%) ACR, 22 of 53 CAHR, 10 of 55 (18.2%) PVN and 3 of 23 (13%) IgA nephropathy recurrence. Twelve patients who had TMA also shown CMV IgM positive serology at the time of diagnosis. Significant differences found between the type of IS therapy and the development of TMA in 272 patients (p<0.001). Patients who had under cyclosporin A (38,5%) therapy were tended to show a higher incidence of TMA development compared to patients with tacrolimus (20,7%) and sirolimus (7,7%) therapy. The incidence of TMA found to be higher in C4d positive AHR (39%) and CAHR (51,4%) groups compared to C4d negative AHR (14,3%) and CAHR ( 18,8%) groups (p<0.05). Graft loss was significantly greater in C4d positive TMA group compared to C4d negative group (p=0.013).

We concluded that AHR, CAHR, PVN, ACR and IgA recurrence are risk factors for TMA in renal allografts. Also, we noted that PTC C4d is a significant risk factor for TMA, and the concurrence of C4d and AMR may portend a greater probability of graft loss due to the effect of TMA.

CITATION INFORMATION: Ozdemir B, Ok Atilgan A, Haberal M. Significance of Thrombotic Microangiopathy in Renal Allografts. Am J Transplant. 2017;17 (suppl 3).

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