Alpha-mannosidosis

Alpha-mannosidosis is caused by a change (also called a mutation or a variant) in the MAN2B1 gene, which causes the gene not to work correctly. The MAN2B1 gene carries the instructions for making the alpha-mannosidase enzyme, which is essential for breaking down large sugar molecules in lysosomes within the body's cells. We normally have two working copies of MAN2B1 in our cells, and we inherit one copy from our biological mother and the other from our biological father. To develop symptoms of alpha-mannosidosis, both copies of MAN2B1 are not working correctly. This is also called autosomal recessive inheritance, which means that both parents of someone with alpha-mannosidosis are carriers of one working and one non-working copy of the MAN2B1 gene. Since each parent has one working copy, they don't have symptoms of alpha-mannosidosis themselves. However, when they have children, they each have a 1 in 2 or 50% chance of passing on the non-working copy to their child. When both parents are carriers, there is a 1 in 4 or 25% chance of both passing on the non-working copy and having a child with alpha-mannosidosis.