[1381] Thrombotic Microangiopathy and Humoral Rejection in Renal Allografts

F Salem, A Chang, SM Meehan. University of Chicago, Chicago, IL

Background: Thrombotic microangiopathy (TMA) in the transplant kidney may be due to many disorders including humoral rejection (HR), calcineurin inhibitor (CI) toxicity, infections and recurrent disease. Linear peritubular capillary (PTC) C4d deposition is a marker of HR. TMA is described as a feature of HR, however few detailed studies of TMA with PTC C4d are available. Here we hypothesize that HR is a significant risk factor for TMA in the renal allograft.
Design: All consecutive renal allograft biopsies, routinely stained for C4d over a period of thirty-eight months (n=744), were reviewed for TMA and C4d status. All patients received CI (cyclosporine or tacrolimus), mycophenolate mofetil and prednisone immunosuppression.
Results: One hundred thirty biopsies had PTC C4d (focal in 30, diffuse in 100) in the observation period. Of twenty-one biopsies with TMA (2.8%), six had PTC C4d. TMA was observed with greater frequency in C4d+ (4.6%) than in C4d- biopsies (2.4%) (odds ratio 1.9, 95% CI 0.7-5.0, p=0.23). Thrombotic and obliterative arteriolopathy was evident in TMA with PTC C4d (83.3%) and in TMA without PTC C4d (93.3%).
Conclusions: TMA was infrequently observed in renal allograft biopsies. There is no significant increase in risk of TMA in allografts with HR compared to those without HR. Arteriolopathy, a morphologic finding not described in HR, is a prominent feature of TMA with and without PTC C4d. These findings suggest that TMA in HR may be spurious and other possible contributing causes of TMA should be sought in allografts with HR.
Category: Kidney (does not include tumors)

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 183, Tuesday Afternoon