Incidence of Thrombotic Microangiopathy in Kidney Transplant Recipients Who Received Tacrolimus: A Multicenter Retrospective Study

Background: Thrombotic microangiopathy (TMA) is a severe condition characterized by thrombocytopenia, hemolytic anemia, and acute kidney failure. TMA can be triggered by infections, medications such as calcineurin inhibitors, and genetic complement defects. In kidney transplant recipients, TMA can lead to graft failure, morbidity, and mortality. Our study aims to identify the incidence of TMA in kidney transplant recipients on tacrolimus versus those not on tacrolimus, and to assess outcomes including transplant rejection, graft failure, and mortality risk. Methods: We conducted a retrospective multi-center cohort study using TriNetX. We identified 1,252 post-renal transplant recipients on tacrolimus and 290 not on tacrolimus. Survival rates after developing TMA were analyzed over 5 years. Secondary endpoints included the incidence of kidney transplant failure in recipients who developed TMA on tacrolimus compared to those not on tacrolimus, and the risk of graft failure, mortality, and TMA incidence over 5 years. Results: TMA occurred in 40.3% of kidney transplant recipients on tacrolimus, compared to 24.4% in the non-tacrolimus group (RR=0.613, 95% CI 0.495-0.760). The 5-year risk of developing TMA was higher in patients on tacrolimus (0.7% vs. 0.2%, P=0.0). Survival probability was 36.1% in tacrolimus patients with TMA, compared to 77.3% in non-tacrolimus patients (RR=0.379, 95% CI 0.291-0.495). The risk of graft rejection over 5 years was higher in patients on tacrolimus with TMA (43.1% vs. 16.95%). The risk of kidney graft failure over 5 years was higher in tacrolimus patients with TMA (38.6% vs. 24.1%, RR=0.624). Kidney transplant recipients on tacrolimus with TMA had a survival rate of 98.4% compared to 99.2% in the other group (Hazard ratio 0.387, 95% CI 0.329-0.453). Our study shows a significant difference in TMA incidence in kidney transplant recipients on tacrolimus compared to those not on tacrolimus (P=0.053). There is a higher risk of graft rejection in patients on tacrolimus who develop TMA. Conclusion: 1. Tacrolimus appears to be an independent risk factor for TMA in kidney transplant recipients. 2. The risk of graft rejection is higher in patients on tacrolimus who develop TMA. 3. The survival rate in kidney transplant recipients who developed TMA was less in those who recieved tacrolimus.