Mucopolysaccharidosis Type VI
How is Mucopolysaccharidosis Type VI inherited?
Mucopolysaccharidosis Type VI (MPS VI) is caused by a change (also called a mutation or a variant) in the ARSB gene which causes the gene to not work correctly. ARSB carries the instructions for making arylsulfatase B, which is an enzyme required for breaking down large sugar molecules called glycosaminoglycans (GAGs). We normally have two working copies of ARSB in our cells and we inherit one copy from our biological mother and the other from our biological father. In order to develop symptoms of MPS VI, both copies of ARSB are not working properly. This is also called autosomal recessive inheritance, which means that both parents of someone with MPS VI are carriers of one working and one non-working copy of the ARSB gene. Since each parent has one working copy, they don't have symptoms of MPS VI 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 of them passing on the non-working copy and having a child with MPS VI. Even if a couple already has one child with MPS VI, it is important to know that they can have another affected child because the chances are 1 in 4 for each pregnancy.
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What does it mean to have inherited a "variant" in the gene for Mucopolysaccharidosis Type VI?
A "variant" is another word for a change in a gene. Sometimes these changes are not associated with causing a genetic disease or condition, and other times they are. Variants can be benign (not disease causing), pathogenic (disease causing), or of unknown significance (possibly disease causing). Looking at a person's genetic testing report can be helpful to know what type of variant or genetic change someone has inherited for mucopolysaccharidosis type VI. If a person is affected by mucopolysaccharidosis type VI, they should have two different disease causing variants in their ARSB genes.