What Your Test Results Mean:

Carriers typically show no symptoms of alpha-mannosidosis; however, carriers are at an increased risk of having a child with alpha-mannosidosis. Risk for the current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor.

Disease Explained:

Alpha-mannosidosis is an autosomal recessive lysosomal storage disorder caused by a deficiency of the enzyme, alpha-mannosidase. Alpha-mannosidase is found in lysosomes, the recycling compartments in the cells of the body. Without this enzyme, carbohydrates accumulate and cause cell death and tissue damage. This disorder is characterized by mental retardation, coarse facial features, skeletal abnormalities, hearing impairment, neurologic motor problems, and immune deficiency. Bone marrow or stem cell transplantation is an effective treatment. Enzyme replacement therapy is currently under investigation.

How the Genetics Works:

Alpha-mannosidosis is an autosomal recessive disorder caused by pathogenic variants in the MAN2B1 gene. In general, individuals have two copies of the MAN2B1 gene. Carriers of alpha-mannosidosis have a single variant in one copy of the MAN2B1 gene while individuals with alpha-mannosidosis have variants in both copies of their genes, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.