Frequently Asked Questions
What is Maroteaux-Lamy syndrome (MPS VI) and what causes it?
What are the signs and symptoms of MPS VI?
How common is MPS VI?
How is MPS VI inherited?
Can two healthy parents have a child with MPS VI?
What should I do if I believe that I or my child might have MPS VI?
How is MPS VI diagnosed?
How is MPS VI treated?
How can I be notified about new developments in MPS VI in the future?
What sources of support are available for individuals and families impacted by MPS VI?
Maroteaux-Lamy syndrome, also called MPS VI (mucopolysaccharidosis VI), is an inherited disorder. People with MPS VI are deficient in a particular enzyme known as arylsulfatase B (ASB). Enzymes are essentially tiny machines which perform various functions within cells. The purpose of ASB is to break down a specific kind of cellular debris—a complex sugar called glycosaminoglycan (GAG) which must constantly be broken down and recycled in order to maintain normal health.
Because people with MPS VI are deficient in this enzyme, excess GAG accumulates within many organs of their body, including the skin, heart, airways, and skeleton. This progressive buildup of unrecycled GAG leads to widespread symptoms that may emerge as early as infancy or as late as adolescence or early adulthood.
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MPS VI causes many different symptoms affecting many parts of the body. Some of these symptoms are also found in other conditions, whereas other symptoms are more specific to MPS VI. Some of the most common symptoms of MPS VI include:
- Short stature
- Gradual coarsening of facial features—including broad nose, flat nasal bridge, thickened tongue and lips, large head, short neck, and unusually prominent eyes
- Cloudy cornea (outer cover of eye)
- Frequent ear infections, sinus infections, or pneumonia
- Noisy breathing or a tendency to get out of breath easily
- Heart murmur, which a physician may notice when listening to the heart with a stethoscope
- Bulging of the abdomen, caused by enlargement of the liver or spleen
- Hernias of the navel or groin
- Stiffness of joints, including the shoulders, elbows, hands, hips, and knees
- Unusual changes in the shapes of various bones
A child or adolescent who is just beginning to show signs of MPS VI may have only 1 or 2 of these symptoms, and they may at first seem very mild. See Signs and Symptoms for a complete list.
The rate at which symptoms appear and worsen varies widely from person to person. Some people have what is called rapidly advancing MPS VI, and may start showing symptoms as early as 6 to 24 months of age. Other people have what is called slowly advancing MPS VI, and may not show significant symptoms until much later.
Unlike some closely related disorders, MPS VI does not affect intelligence. Despite looking different and developing physical disabilities, people with MPS VI typically have normal intelligence.
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MPS VI is very rare. It happens in only about 1 out of every 340,000 births. MPS VI is thought to affect about 1,100 people worldwide.
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MPS VI is caused by an inherited genetic change that causes a person to be deficient in the enzyme arylsulfatase B (ASB).
We carry 2 copies of almost all of our genes, including the gene for ASB. People with MPS VI are deficient in the ASB enzyme because they happen, by chance, to have inherited 2 non-working copies of the gene for ASB (1 copy from each parent). In contrast, people who have 1 working copy and 1 non-working copy of the ASB gene are called carriers. Carriers make enough ASB to remain healthy, and do not have MPS VI disease, but they can still pass their non-working copy of the ASB gene on to their children (they have a 1 in 2 chance of doing this). When 2 carriers of the non-working ASB gene have children together, they are at risk of having a child with MPS VI (each child born to such parents has a 1 in 4 chance of having MPS VI).
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Yes—in fact people with MPS VI are almost always born to healthy couples. In order to have a child with MPS VI, both parents in a couple need only be carriers. Because carriers have 1 working copy of the ASB gene in addition to 1 non-working copy, they make enough ASB enzyme to remain healthy, but can still pass their non-working copy of the ASB gene on to their children.
When a child develops MPS VI, it is because both of the parents, by chance, were carriers, and happened to pass their non-working copy of the ASB gene on to that child.
Because MPS VI is so rare, it is unlikely that a man and a woman would both be carriers of MPS VI. A prospective parent would have no reason to think that he or she might be an MPS VI carrier. So parents should not feel as though they could have prevented MPS VI—we are all carriers of a few non-working genes and have no way of knowing until, by chance, a disease occurs.
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MPS VI can cause some very serious, and irreversible, complications such as blindness and paralysis. Getting specialized medical attention as early as possible provides the best hope of preventing or alleviating these complications.
Unfortunately, diagnosis of MPS VI is often delayed; one study suggested the average delay is 2.5 years after noticeable symptoms appear. This is partly because, since MPS VI is so rare, many doctors have rarely or never seen a person with MPS VI, and so they are unlikely to suspect it.
If you have any reason to think that you, your child, or another family member may be developing the early signs of MPS VI, it is important to see a specialist who can recognize it as soon as possible—this means seeing a geneticist or metabolic specialist. Your regular doctor can help you locate one.
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Even though diagnosis of MPS VI is often delayed, once a person sees a geneticist or metabolic specialist definitive diagnosis can happen relatively quickly. This is because MPS VI can be diagnosed using laboratory tests.
One type of test, called urine GAG analysis, measures the amount of complex sugars called glycosaminoglycans, or GAGs, in the urine (people with MPS VI typically have unusually high levels of GAG in their urine). Other tests measure the amount of arylsulfatase B (ASB) enzyme in a person's blood cells or skin cells (people with MPS VI have unusually low amounts of this enzyme).
These tests are highly specialized, and therefore should be carried out by an experienced laboratory. A geneticist or metabolic specialist will know how to order these laboratory tests and how to interpret the results.
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The goals for managing MPS VI are to improve quality of life, to slow progression of the disease, and to prevent permanent tissue damage. Symptom-based treatments can play an important role in maintaining quality of life, and in some cases even prevent the occurrence of irreversible disabilities such as blindness, deafness, or paralysis.
One approach to treating MPS VI is a procedure called hematopoietic stem cell transplant (HSCT), in which a person is transplanted with cells from a healthy individual. These transplanted cells, since they come from a person without MPS VI, produce small amounts of the deficient enzyme (arylsulfatase B) which people with MPS VI don't have enough of. HSCT has produced benefits in some people with MPS VI, but unfortunately it is a realistic option for only a small number of patients, owing in part to the significant medical risks associated with it.
Enzyme replacement therapy (ERT) is another approach designed to address the underlying deficiency of the enzyme (arrylsulfatase B) by replacing the missing enzyme through regular intravenous infusion (IV). The enzyme travels through the bloodstream and enters cells in various organs of the body, where the enzyme is then able to break down the GAG that has been stored. To learn more about ERT for MPS VI, visit www.naglazyme.com.
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An international initiative has been launched to improve awareness and knowledge of MPS VI and to advance its diagnosis and treatment. Register for this program to receive updates on the latest development in MPS VI and treatment options for MPS VI.
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A number of organizations provide support, information, or services to families and individuals affected by MPS VI. A full listing of these organizations may be found in the Resources web page.
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