Case Report: Donor-derived early T-cell precursor acute lymphoblastic leukemia following an allogeneic hematopoietic stem cell transplantation for pediatric severe aplastic anemia.

Donor cell leukemia is a rare but severe complication following an allogeneic hematopoietic stem cell transplantation (allo-HSCT), particularly in patients with non-malignant diseases, due to its aggressive clinical progression and poor prognosis. In recent years, with the increasing number of umbilical cord blood stem cell transplantation cases, umbilical cord blood-derived donor cell leukemia has garnered growing attention. Although umbilical cord blood cells may inherently carry tumor precursor characteristics, host environmental factors, immunosuppression, and chemotherapy during transplantation can exacerbate their transformation into leukemia. Herein, we report a clinical case of a pediatric patient with severe aplastic anemia who developed umbilical cord blood-derived early T-cell precursor acute lymphoblastic leukemia 2 years and 5 months after receiving an allo-HSCT. Despite multiple chemotherapy regimens, the patient ultimately failed to achieve remission and succumbed to the disease. Although this outcome is regrettable and highlights the refractory nature of post-transplant donor cell leukemia, further investigation into its molecular biological mechanisms is warranted to develop early prevention strategies and more effective therapeutic approaches.