Donor stem cell‐derived paroxysmal nocturnal hemoglobinuria after umbilical cord blood transplantation

Donor cell-derived hematological disorder (DCHD) is a rare complication of allogeneic hematopoietic stem cell transplantation (HSCT). The number of reports of DCHD has been increasing in the last decade, which likely reflects the growing number of HSCTs and the improved ability to identify the donor cell origin. Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematological disorder arising in the context of clonal expansion of hematopoietic stem cells harboring a somatic mutation in phosphatidylinositol glycan anchor biosynthesis, class A. We report here a patient with adult T-cell leukemia/lymphoma, who developed PNH 7 years after umbilical cord blood transplantation. The patient has maintained complete remission with full-donor chimerism after HSCT. Thus, PNH was derived from stem cells of donor origin. The immature immune environment in the recipient after cord blood transplantation might have contributed to the rapid clonal expansion for neonatal stem cells in cord blood to develop typical symptomatic PNH in a short period. To the best of our knowledge, this is the first report in the literature of a case of PNH that developed in donor stem cells after HSCT.