Characteristics of late transplant‐associated thrombotic microangiopathy in patients who underwent allogeneic hematopoietic stem cell transplantation

Transplant-associated thrombotic microangiopathy (TA-TMA) has a wide range of presentations after hematopoietic stem-cell transplantation (HSCT). We retrospectively studied the risk factors and outcomes of patients with early (≤day 100) and late (>day 100) TA-TMA. Among the 1451 HSCT recipients, early TA-TMA occurred in 45 (3.1%) patients at a median of 27 (3-91) days, and late TA-TMA in 39 (2.7%) patients at a median of 303 (122-2595) days. Patients with early TA-TMA were more likely to have high blood calcineurin-inhibitor levels (P < .001) and acute graph-vs-host disease (GVHD, P < .001), while late TMA patients were more likely to have chronic GVHD (P < .001). The estimated median overall survival after onset of TMA for the entire cohort was 6 months. The estimated median overall survival was not reached in patients with an improvement of TMA vs 2 months in patients with no improvement (P < .001). In the early TMA group, older age (for every 10 years, HR 1.40; 95% CI 1.00-1.94; P = .049) and bacterial infection (HR 2.42; 95% CI 0.98-6.00; P = .056) were positively associated with mortality. Switching to MMF treatment (HR 0.40; 95% CI 0.16-0.99; P = .047) and improvement of TMA (HR 0.08; 95% CI 0.03-0.25; P < .001) were negatively associated with mortality in the multivariate analysis. In the late TMA group, the improvement of TMA was the only independent predictor associated with a lower risk of death (HR 0.05; 95% CI 0.02-0.19; P < .001). Mortality rates in both early and late TMA remain unacceptably high. Future studies are needed for early diagnosis, trigger identifications, and use of targeted treatments.