Abstract

Abstract Context Mucopolysaccharidosis (MPS) requires urgent treatment to prevent neurological damage. While gene therapy holds promise for effectively treating these diseases with minimal toxicity, access remains limited for most patients. Consequently, advancing allogeneic hematopoietic stem cell transplantation (HSCT) for young children is crucial. Since the 2010s, cord blood (CB) transplants with reduced‐toxicity conditioning (RTC) have become the standard of care. Patients and methods Recent reports in France indicate a significant incidence of graft failures (GF), prompting a large‐scale retrospective study from the French‐speaking bone marrow transplantation society's registry, to understand GF risks, guide clinicians in selecting transplant platforms, and describe outcomes of second HSCT in young patients. Results This report analyses 93 children who underwent HSCT for MPS between 2000 and 2020. The GF rate was notably high (22.6% at day 100), primarily associated with the donor's HLA compatibility and the recipient's age. Well‐matched CB and RTC were not found to be risk factors for GF. This study also details the procedures for second and third transplants in patients who rejected their first HSCT. Conclusion In the era of RTC, CB remains a viable and expedient option for MPS transplantation.