Specific treatments for Alpha Mannosidosis

Hematopoietic stem cell transplantation (HSCT)¹

Rationale for treatment: with this condition, all cells are without α-mannosidase activity. The rationale for HSCT in this setting is that enzyme-producing donor cells repopulate the host tissues and transfer enzyme to nearby enzyme-deficient host cells.

The outcomes from HSCT have been reported as variable with mixed reports of the neurocognitive impact of the therapy.^2,3

A number of unpublished HSCTs have been performed.⁴However, in 2004, results were published for four patients, aged 3 to 23 years, who had undergone the procedure, suggesting that intellectual function in these patients stabilised, with improvement in adaptive skills and verbal memory function (some with improvements in hearing for speech frequencies only).⁵

The possible benefits of HSCT must be weighed against the overall risk of the procedure, related to morbidity and mortality.⁶The benefits are greater in younger patients, before the disease has progressed further.^{7 8}

Transplant-related complications are more frequent and severe in older patients, which means HSCT is more of an option in the first years of life. This makes early identification of affected patients critical.⁹

Enzyme Replacement Therapy

Enzyme replacement therapy (ERT) is a therapeutic alternative in a number of lysosomal storage diseases.¹⁰

An ERT is approved for treatment of alpha-mannosidosis in the European Union.¹¹