Hematopoietic stem cell transplantation in inborn errors of metabolism-a retrospective analysis on behalf of the pediatric disease working party from the Brazilian Society of Bone Marrow Transplantation and Cellular Therapy.

Hematopoietic stem cell transplantation (HSCT) is an established treatment for selected patients with inborn errors of metabolism. In this first report from the PDWP-SBTMO, we included 105 patients transplanted between 1988 and 2021 across six Brazilian HSCT centers. The most prevalent diseases were X-linked adrenoleukodystrophy (n = 61) and mucopolysaccharidosis (type I n = 20; type II n = 10), with a median age at HSCT of 8.7 years and 2.1 years, respectively. Most conditioning regimens were myeloablative and busulfan-based. With a median follow-up of 6.7 years, the 5-years overall survival (OS) was 75% (95% CI, 0.65-0.82) with a superior 5-years OS for those transplanted after 2010 (87% vs. 63%, p = 0.01). Higher risk of death was associated with the use of haploidentical donor (HR8.86, p 0.021), unrelated cord blood (HR 8.76, p 0.005), unrelated donor (HR 5.91, p 0.02), and for HSCT performed before 2010 (HR 4.16, p = 0.0015). The CI of acute GVHD was 24.8%, while chronic GVHD was 9.5%. Major causes of death were infections (n = 8), GVHD (n = 6), and neurologic progression (n = 3). Despite improvements in transplant outcomes since 2011, challenges persist, emphasizing the need for early diagnosis, timely transplantation and expanding HSCT centers with expertise in the field.