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- Mucopolysaccharidosis (MPS) is a disorder caused by genetic errors, or mutations, in any of the genes that produce the enzymes responsible for glycosaminoglycan degradation. Because MPS is inherited, a family history of the disorder is the primary risk factor for MPS.
- Autosomal recessive inheritance: Most types of mucopolysaccharidosis (MPS) are inherited as autosomal recessive traits. MPS II or Hunter syndrome is the only form of MPS that is X-linked dominant. A person must inherit two copies of the genetic mutation (one copy from each parent) to develop a recessive form of MPS. People who inherit a mutation from only one parent are called "carriers," and they may pass the mutation to their children.
- If only one parent has one copy of the mutated gene, then each child will have a 50% chance of inheriting one mutated gene and also being a carrier. If both parents are carriers, each child has a 25% chance of inheriting two mutated genes, a 50% chance of inheriting only one mutation, and a 25% chance of inheriting neither of the mutations.
- If one parent has MPS and the other parent does not carry the trait, then all of the children will be carriers. If one parent has MPS and the other parent is a carrier, then each child has a 50% chance of having MPS and a 50% chance of being a carrier. If both parents have MPS, then all of their children will also have MPS.
- X-linked dominant inheritance: MPS II or Hunter syndrome is an X-linked dominant inherited genetic condition. Normal individuals have two copies of most genes (one inherited from the father and one from the mother). A person needs to inherit only one copy of the defective gene to develop a dominant disease. A deficiency or mutation in the enzyme iduronate sulfatase, which is located on the X chromosome, may cause MPS II.
- Females have two copies of the X chromosome, but males have one X chromosome and one Y chromosome. Males inherit an X chromosome from the mother and a Y chromosome from the father, so a male can only inherit MPS II from the mother. Therefore, a female needs to inherit two mutant copies to develop MPS II (one from each parent), whereas a male only needs to inherit one mutant copy to develop the condition. MPS II is more common in males that females. Females who inherit only one mutant copy are called "carriers." Female carriers may exhibit some mild symptoms.
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