The use of partially HLA-mismatched donors for allogeneic transplantation in patients with mucopolysaccharidosis-I.

Allogeneic bone marrow transplantation (BMT) from an HLA-matched sibling appears to improve survival and diminish some of the physiologic derangements seen in children with mucopolysaccharidosis (MPS)-I (Hurler Syndrome), an inherited metabolic storage disease resulting from the lack of alpha-L-iduronidase enzyme activity. Death is usually expected in the first decade of life. Unfortunately, most patients lack an HLA-matched sibling donor and alternative donors have been identified for transplant. This study reports on a five-year median follow-up (range: 985-2,355 days) in 11 Hurler Syndrome patients who underwent allogeneic BMT from partially mismatched related donors (PMRDs). The median age was 20 months (range: 11-44 months). The overall survival rate was 64% (95% CI 34-94%). The overall graft failure rate (36%) was higher than reported with matched sibling BMT. All patients with sustained engraftment experienced improvement in physical manifestations, such as corneal opacity, gum and tongue hypertrophy, hepatosplenomegaly and joint mobility. Skeletal abnormalities, such as dysostosis-multiplex, were stabilized but not reversed. Some patients have continued to show decline in neuropsychometric testing, while others appear to stabilize and one has demonstrated improvement. Until better methods for replacing enzyme activity are developed, BMT from a matched sibling of alternative donors can be considered a viable intervention for Hurler Syndrome patients to achieve partial improvement or stabilization from the deterioration caused by substrate storage, particularly in minimally affected patients early in life.