Thrombotic Microangiopathy in Renal Transplant Recipients

Background and Aim: Thrombotic microangiopathy (TMA) is a disease of microvasculature, triggered by numerous immunological and nonimmunological factors. The aim of this study is to identify the incidence, etiology, and clinical characteristics of posttransplant TMA in renal allografts and its impact on graft outcome. Patients and Methods: In this retrospective study, the records of patients who underwent renal transplantation between January 2013 and December 2017 were reviewed, and those recipients who had allograft biopsy-proven TMA were analyzed. Based on the clinical characteristics and investigations, the recipients were divided into two groups: those with systemic features of TMA and those with allograft-limited TMA. The clinical course and graft outcome of both the groups were compared and analyzed. Results: The number of patients who underwent renal transplantation during the study period was 212. Out of them, 16 patients had biopsy-proven TMA. Five patients had TMA with systemic features and the remaining 11 patients had allograft-limited TMA. In this study, the incidence of TMA among postrenal transplant recipients was 7.5%. The most common cause for TMA was acute antibody-mediated rejection (ABMR), followed by TMA due to tacrolimus toxicity. In one patient, TMA was secondary to disseminated tuberculosis (TB). TB as a cause of TMA is rarely reported. One-year graft survival in patients with allograft-limited TMA was 72.7% when compared to 50% in patients with systemic TMA, but this difference was statistically insignificant ( P = 0.2). The graft loss was high in patients with TMA secondary to ABMR in both the groups. Conclusion: One-year graft survival is better in patients with allograft-limited TMA. Diligent search for an etiology for TMA should be made in all patients with TMA, as the treatment differs between each category.