Predictors of Long-Term Clinical Outcome in Hurler Syndrome Patients after Successful Hematopoietic Cell Transplantation: An International Study

s / Biol Blood Marrow Transplant 20 (2014) S72eS90 S79 median age of 16 (2-80) months at transplantation with a median follow-up of 8.9 (3-22.6) years after last HCT. Posttransplant leukocyte IDUA enzyme levels below the lower reference were seen in 25% of patients due to mixedchimerism or the use of a carrier donor. Following successful HCT, the clinical course of HS patients is strikingly improved, evident in all organ systems. Residual disease burden is present in the majority of the patients with high variability between patients. A better cognitive status at HCT was a major predictor for superior cognitive development after HCT (figure 1). Significant predictors for superior long-term outcome in all organ systems were the presence of “normal IDUA enzyme levels obtained after HCT” and a “younger age at transplantation”. See the association between the leukocyte IDUA enzyme level obtained after HCTand surgical intervention for cord compression and growth, in figure 2 and 3 respectively. Conclusion: Although HCT significantly improved the clinical course in HS patients, residual disease burden was observed in the majority of transplanted HS patients. Using exclusively non-carrier donors and accepting only full donor-chimerism will improve the prognosis of HS patients. Reducing the age at HCT through newborn screening could further improve the outcomes of HS patients after HCT.