Allogeneic hematopoetic stem cell transplantation in pediatric myelodysplastic syndromes: Improved outcomes for de novo disease. Pediatr Transplantation 2011: 15: 334-343. © 2011 John Wiley & Sons A/S. Abstract: We report 23 consecutive pediatric patients with MDS who received allogeneic HSCT on IRB approved protocols between 1992 and 2009 at Children's Memorial Hospital (Chicago, IL). Nine patients had de novo MDS, whereas 14 patients had treatment-related MDS. All patients had a documented cytogenetic abnormality, and monosomy 7/7q- was seen in 12 patients (52%). Fourteen of 23 patients received a myeloablative conditioning regimen; RIC regimens were used for the remaining nine. Five patients relapsed post-transplant, including four patients who received RIC transplant and four patients with treatment-related MDS. For the entire group, estimated five-yr RFS and OS were 47% and 50%, respectively. Treatment-related MDS was associated with decreased RFS in comparison with de novo MDS (33% vs. 70%, p = 0.05). Five-year OS rates reached 80% for those with de novo MDS. RIC regimens were associated with decreased three-yr RFS in comparison with myeloablative regimens (22% vs. 68%, p = 0.02). There was no correlation of survival with blast count at diagnosis, IPSS score, cytogenetic abnormality, donor type, or HLA match. Larger series are needed to confirm prognostic factors so that higher-risk patients can be targeted with novel approaches.