Effective treatment of α-mannosidosis by allogeneic hematopoietic stem cell transplantation

Objectives To study the efficacy of hematopoietic stein cell transplantation (HCT) for ameliorating the clinical manifestations of alpha-mannosidosis. Study design Four patients with alpha-mannosidosis underwent allogenic HCT at the University of Minnesota. Diagnosis was established by assay of leukocyteo alpha-mannosidase activity level. Physical features, donor engraftment, leukocyte alpha-mannosidase activity, neuropsychologic function, and hearing were monitored before and after transplantation, with follow-up ranging from 1 to 6 years. Results All 4 patients showed slowing of their neurocognitive development and sensorineural hearing loss before HCT. All patients are alive, with normalization of leukocyte enzyme activity after HCT. Intellectual function has stabilized, with improvement in adaptive skills and verbal memory function in 3 of 4 patients. Hearing has improved to normal or near normal for speech frequencies in 3 patients. No new skeletal abnormalities have developed. Conclusions HCT can halt the progressive cognitive loss in patients with alpha-mannosidosis. Early diagnosis and treatment with HCT is critical for optimal results.