Mucopolysaccharidosis type II (Hunter syndrome)

Mucopolysaccharidosis type II (MPS II) is also known as Hunter syndrome and it is an X-linked condition meaning that it affects males but the majority of women who carry MPS II will not have any symptoms of the condition.

MPS II is a type of lysosomal storage disorder which is caused when the body cannot break down a sudstance known as glycosaminoglycans (GAGs). These GAGs build up in the body and cause the symptoms of the condition.

MPS II affects multiple parts of the body including the brain and central nervous system, respiratory system, heart and other muscles. The symptoms of MPS II can present from early infancy to later in childhood and will get worse over time although how fast they worsen varies from person to person.

There are two types of MPS II, called the severe and mild types. Both types affect many different parts of the body, but people with severe MPS II also experience a decline in thei intellectual function and their symptoms get worse faster than people with the mild form. People with the severe form begin to experience major symptoms between the ages of 6 and 8 and sadly they will often die between ages 10 and 20y. People with mild MPS II ususally live into adulthood and they do not experience the problems with their intelectual development.

Quick facts about Mucopolysaccharidosis type II (Hunter syndrome)
Genes: IDS
Inheritance: X-linked
Relevant resources for Mucopolysaccharidosis type II (Hunter syndrome)

A quick genetics rundown

As humans we have about 23,000 genes. These genes are like tiny instruction manuals that influence our health, growth and development. We inherit half of our genes from our biological mum and the other half from our biological dad. These genes are lined up on structures called chromosomes. Most of us have 23 pairs of chromosomes. The first 22 pairs are called autosomes and for the most part - these are the same among men and women. The 23rd pair determine our sex - two X chromosomes for a female and one X and one Y chromosome for males.

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How is Mucopolysaccharidosis type II (Hunter syndrome) inherited?

Mucopolysaccharidosis type II (Hunter syndrome) is an X-linked condition. X-linked conditions occur when there is a genetic variation on the X-chromosome. For these conditions, the sex of the parent who passes on the gene variation influences the risk for the children.

If the father is affected, all his daughters will have a variation on one of their X-chromosomes and be healthy carriers. Sons can only inherit these x-linked conditions from their mother and therefore, in this situation, will not be affected by the disease.

If the mother is a healthy carrier of an X-linked variation and has a son, there is a 50% chance that they could inherit this variant and be affected by the disease. If they have a daughter, there is a 50% chance that they will be a healthy carrier (just like her mum).

Another way of looking at this is that there is a 25% chance of having an affected son and a 75% chance that the child will not be affected by the disease.

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What is carrier screening?

Carrier testing is like a checkup for your genes. It tests to see if you carry a gene variation that could cause a serious genetic disease in your child. Eugene offers an inclusive genetic carrier screening panel that includes Mucopolysaccharidosis type II (Hunter syndrome), but there's a total 301 conditions that can be tested.

Eugene’s carrier test is a clinical grade test that can be done from the comfort of your own home — it’s just a saliva test. You're also paired with a genetic counsellor who provides mindful support and guidance every step of the way.

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Should parents screen for Mucopolysaccharidosis type II (Hunter syndrome) before or early in pregnancy?

The biggest benefit of screening for Mucopolysaccharidosis type II (Hunter syndrome) is that it can help future parents understand their reproductive risk so they can be ready and empowered to make more informed decisions. If neither partner are carriers, it provides reassurance and peace of mind that the risk of having a child with a genetic disease is low.

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