Transplant-associated thrombotic microangiopathy (TA-TMA) is a life-threatening complication of hematopoietic stem cell transplantation in which systemic complement activation induces endothelial injury, leading to microangiopathic hemolytic anemia, thrombocytopenia, and organ dysfunction. TA-TMA often progresses rapidly and has historically been associated with high mortality. Over the last decade, increasing recognition of complement activation as a central driver of TA-TMA has shifted managem