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Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder caused by deficient activity of the iduronate-2-sulfatase. This leads to accumulation of glycosaminoglycans (GAGs) in the lysosomes of various cells. Although it has been proposed that bone marrow transplantation (BMT) may have a beneficial effect for patients with MPS II, the requirement for donor-cell chimerism to reduce GAG levels is unknown. To address this issue, we transplanted various ratios of normal and MPS II bone marrow cells in a mouse model of MPS II and analyzed GAG accumulation in various tissues. Chimerism of whole leukocytes and each lineage of BMT recipients' peripheral blood was similar to infusion ratios. GAGs were significantly reduced in the liver, spleen, and heart of recipients. The level of GAG reduction in these tissues depends on the percentage of normal-cell chimerism. In contrast to these tissues, a reduction in GAGs was not observed in the kidney and brain, even if 100 % donor chimerism was achieved. These observations suggest that a high degree of chimerism is necessary to achieve the maximum effect of BMT, and donor lymphocyte infusion or enzyme replacement therapy might be considered options in cases of low-level chimerism in MPS II patients.

Objective: To evaluate the effect of bone marrow transplantation in children with Hunter syndrome., Study Design: Eight boys received a bone marrow graft between the ages of 3 and 16 years from 1990 to 2000. In 6 cases, the donor was a sibling with identical HLA status, in 1 case an unrelated donor with HLA-compatible, and in 1 case a mismatched unrelated donor. A complete multidisciplinary evaluation was performed yearly., Results: Successful engraftment was achieved in all patients, with the proportion of donor cells reaching > or =95% 1 month after transplantation in all patients. Patients have been followed from between 7 and 17 years and all are still alive, except for 1 boy who died at the age of 10 from unrelated causes. Cardiovascular abnormalities stabilized in all patients, hepatosplenomegaly resolved, and joint stiffness improved, Perceptual hearing defects remained stable, and transmission hearing defects improved. Only 1 child required subsequent surgery to correct kyphosis. Neuropsychological outcome was variable and appeared to be related to the severity of the syndrome., Conclusions: Bone marrow transplantation is effective on the no neuropsychological symptoms of Hunter disease.