Treatment outcomes for MPS I patients. Comparison of substrate reduction, expressed as the ratio of accumulated dermatan sulfate (DS) to nonaccumulated chondroitin sulfate (CS),¹⁸  in patients who have received transplantation from a heterozygous donor, transplantation from an unrelated donor, and pharmacological ERT. The metabolic correction is better for those receiving transplantation from an unrelated donor than for those receiving transplantation from a heterozygous family donor, reflecting the better enzyme delivery by the donor with 2 copies of the enzyme gene. The metabolic correction is lowest for the ERT-treated patients and, presumably, the enzyme delivery is least good for these patients.