What Is Hunter Syndrome (MPS 2)?

Hunter syndrome is an inherited disease caused by a faulty gene.

Children with Hunter syndrome lack an enzyme called iduronate 2-sulfatase that the body needs to digest sugar. As a result, undigested sugar molecules build up in the body.

This causes progressive organ damage, especially to the brain and heart, and breathing problems.

The medical name for Hunter syndrome is mucopolysaccharidosis type 2, or MPS 2.

How Common Is Hunter Syndrome (MPS 2)?

About 1 in 100,000 to 170,000 babies are born with MPS 2.

It nearly always occurs in males. Females can carry the gene that causes MPS 2.

What Causes Hunter Syndrome?

Changes in the IDS gene cause MPS 2.

This gene tells the body how to make the enzyme you need to break down sugar. If you can't break sugar down, the molecules build up and affect the body's organs.

The gene that causes Hunter syndrome is on the X chromosome.

Because males only have one X chromosome, one altered gene can cause the condition.

Females have two X chromosomes, meaning they need two copies of the faulty gene to get MPS 2. This is why Hunter syndrome is very rare in females.

Hunter Syndrome (MPS 2) Symptoms

MPS 2 mostly affects boys, and symptoms often appear around age two.

Hunter syndrome symptoms include:

  • Changes in facial features, with lips and tongue getting thicker and cheeks getting larger.
  • A very large head.
  • Joint stiffness, especially in the hands and wrists.
  • Recurring upper respiratory infections.
  • Chronic runny nose.
  • Frequent ear infections and hearing loss.
  • Enlarged liver and spleen.
  • Failure to grow as normal after about age five.
  • Bone and joint abnormalities that keep getting worse.

Types of Hunter Syndrome

There are two types of Hunter syndrome (MPS 2): severe and mild.

Severe Hunter syndrome

For children with severe MPS 2, the disease will progress more quickly.

By around age 8, they:

  • Will struggle with basic functional and cognitive skills.
  • May have breathing problems, heart issues, and trouble moving as bones get weaker and joints get stiffer.
  • May also have behavioral issues and trouble sleeping.

Mild Hunter syndrome

The disease progresses more slowly for children with the mild type of MPS 2.

They often don't have cognitive issues. But they will have heart and breathing issues into adulthood.

Diagnosing Hunter Syndrome in Children

If a doctor suspects MPS 2, they’ll test your child's urine to see if there's a build-up of sugar molecules. They will also order a blood test to measure enzyme levels.

Testing a child's genes can confirm the MPS 2 diagnosis.

Hunter Syndrome Treatment

There’s no cure for Hunter syndrome.

Enzyme replacement drugs may help some children. This type of medicine does the job of the missing enzyme.

A stem cell transplant can also help some children with MPS 2. Transplant isn't an option for all children with MPS 2, but your child's doctor may discuss it with you.

Some supportive techniques that may help kids with MPS 2 include:

  • Physical therapy (PT). PT can help improve a child's mobility and help with joint stiffness. We can also provide adaptive devices, like walkers and wheelchairs, to help them move better.
  • Speech therapy. This technique helps children with speech and language problems. This is especially helpful since MPS 2 can affect hearing and the ability to talk.
  • Medicine. Doctors can prescribe medicines to help children sleep better.
  • Breathing devices. These can help open up a child's airways.

Doctors may also suggest surgery to address certain symptoms. For instance, surgery to replace a damaged heart valve can extend a child's life.

Your Child's Hunter Syndrome (MPS 2) Consult and Care: What to Expect

If a doctor diagnosed your child with Hunter syndrome, we want you to know you're not alone. The Center for Rare Disease Therapy (CRDT) at UPMC Children's Hospital of Pittsburgh is here to help.

To make an appointment for your child or refer a patient for MPS 2 care, contact us by:

Here's what you can expect when you come to us for your child's first consult.

What should I expect at my child's first Hunter syndrome visit?

You can expect your first visit to take from 4 hours to a few days. Your child will have a thorough exam from Dr. Deepa Rajan, the NDRD program director.

She will make or confirm a precise diagnosis and find out how much the disease has progressed.

Because we work as a team at the center, other doctors and staff might see your child during your visit.

These may include experts in:

  • Genetic diseases.
  • Brain diseases.
  • Child development.
  • Hearing.
  • Physical therapy.

During your visit, we'll talk with you about:

  • Next steps for your child in the near future.
  • Options for treating your child's Hunter syndrome.
  • Ways to improve your child's quality of life at home.

We'll discuss the details of stem cell transplant if we think it might be a good option for your child. We want to make sure you know what the transplant entails and how you may need to prepare.

By the end of your visit, you'll have a care plan tailored to your child's MPS 2 needs. We'll also schedule a follow-up visit in three months.

You'll meet our nurse practitioner, who can answer questions by phone or video call between visits.

Before you leave, feel free to ask us about your child's diagnosis, treatment, or anything else.

When should I expect the results if my child had tests at the Center for Rare Disease Therapy?

We'll call within 2 weeks to review the test results and the next steps for your child's MPS 2 care.

You can also find your child's test results on MyCHP — Children's patient portal. MyCHP portal lets you manage your child's health online.

It's free to kids getting treatment at UPMC Children's and their parents or guardians.

Partners in Your Child's Hunter Syndrome Care

A rare disease like Hunter syndrome affects the whole family.

At the CRDT, every child we see receives a tailored treatment plan and family-centered care.

We treat each family member as our partner. The best care happens when we merge our MPS 2 knowledge with your insight into what's best for your child.

Center for Rare Disease Therapy patient storiesMeet Our Rare Disease Center Patients

Learn how others are finding help and hope for their child’s rare disease through the expertise at UPMC Children’s.

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Contact Us About Your Child’s Hunter Syndrome

At the CRDT, every child diagnosed with a rare disease receives a tailored treatment plan and family-centered care.

For an appointment, consult, or referral, contact us:

We’ll be in touch within 2 business days.