Definition

What is Hunter syndrome?

Hunter syndrome is a very rare, inherited genetic disorder caused by a missing or malfunctioning of an enzyme called iduronate-2-sulfatase which facilitates breakdown of glycosaminoglycans. Because the body doesn’t have enough of the enzyme to break down certain complex molecules, the molecules build up in harmful amounts.

In Hunter syndrome, the buildup of massive amounts of glycosaminoglycans eventually causes permanent, progressive damage affecting appearance, mental development, organ function and physical abilities.

How common is Hunter syndrome?

Hunter syndrome is extremely rare. It appears in children as young as 18 months. It mainly occurs in boys, although very rarely it has been observed in girls. Please discuss with your doctor for further information.

Symptoms

What are the symptoms of Hunter syndrome?

Hunter syndrome is one type of a group of inherited metabolic disorders called mucopolysaccharidoses (MPSs), and Hunter syndrome is referred to as MPS II.

Hunter syndrome symptoms vary and range from mild to severe. Symptoms aren’t present at birth, but often begin around ages 2 to 4.

Signs and symptoms may include:

  • An enlarged head (macrocephaly)
  • Thickening of the lips
  • A broad nose and flared nostrils
  • A protruding tongue
  • A deep, hoarse voice
  • Abnormal bone size or shape and other skeletal irregularities
  • A distended abdomen, as a result of enlarged internal organs
  • Diarrhea
  • White skin growths that resemble pebbles
  • Joint stiffness
  • Aggressive behavior
  • Stunted growth
  • Delayed development, such as late walking or talking

There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.

When should I see my doctor?

If you or your loved one has changes in facial appearance, a loss of previously acquired skills, or any signs or symptoms listed above; or has any questions, please consult with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.

Causes

What causes Hunter syndrome?

As stated, Hunter syndrome is caused due to missing or malfunctioning enzyme called iduronate-2-sulfatase which facilitates breakdown of glycosaminoglycans. The chromosome which causes malfunctioning of the enzyme is usually inherited from the mother.

Enzyme iduronate-2-sulfatase is usually present in the lysosomes. Under normal circumstances, the nutrients present in the body are broken down by lysosomes to build healthy tissues, bones, cartilage etc. When iduronate-2-sulfatase does not function adequately it results in gradual buildup of glycosaminoglycans causing Hunter syndrome.

Risk factors

What increases my risk for Hunter syndrome?

There are many risk factors for Hunter syndrome, such as:

  • Family history. Hunter syndrome is caused by a defective chromosome, and a child must inherit the defective chromosome to develop the disease. Hunter syndrome is what’s known as an X-linked recessive disease. This means that women carry the defective disease-causing X chromosome and can pass it on, but women aren’t affected by the disease themselves.
  • Sex. Hunter syndrome nearly always occurs in males. Girls are far less at risk of developing this disease because they inherit two X chromosomes. If one of the X chromosomes is defective, their normal X chromosome can provide a functioning gene. If the X chromosome of a male is defective, however, there isn’t another normal X chromosome to compensate for the problem.

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is Hunter syndrome diagnosed?

Babies born with Hunter syndrome almost always appear healthy at birth. Changes in facial features are often the first noticeable sign that something’s not right.

Blood, urine or tissue samples can be checked for the deficient enzyme or for excess amounts of the complex sugar molecules associated with this disorder. A genetic analysis can confirm the diagnosis.

Because Hunter syndrome progresses slowly and its signs and symptoms overlap with a number of other disorders, definitive diagnosis may take some time.

Prenatal testing

Prenatal testing of the fluid that surrounds the baby (amniocentesis) or of a tissue sample from the placenta (chorionic villus sampling) can verify if your unborn child carries a copy of the defective gene or is affected with the disorder.

How is Hunter syndrome treated?

Because there’s no cure for Hunter syndrome, treatment focuses on managing signs, symptoms and complications to provide some relief for your child as the disease progresses.

  • Relief for respiratory complications. Removal of tonsils and adenoids can open up your child’s airway and help relieve sleep apnea. But as the disease progresses, tissues continue to thicken and these problems can come back.
    Breathing devices that use air pressure to keep the airway open — such as continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) devices — can help with upper airway obstructions and sleep apnea. Keeping your child’s airway open can also help avoid low blood oxygen levels.
  • Addressing heart complications. Your child’s doctor will want to watch closely for cardiovascular complications, such as high blood pressure, heart murmur and leaky heart valves. If your child has severe cardiovascular problems, your doctor may recommend surgery to replace heart valves.
  • Treatment for skeletal and connective tissue problems. Because most children with Hunter syndrome don’t heal well and often have complications after surgery, options are limited for addressing skeletal and connective tissue complications. For example, surgery to stabilize the spine using internal hardware is difficult when bones are fragile.
    Your child’s joint flexibility can be improved with physical therapy, which helps address stiffness and maintain function. However, physical therapy can’t stop the progressive decline of joint motion. Your child may eventually need to use a wheelchair because of pain and limited stamina.
    Surgery can repair hernias, but because of weakness in connective tissues, results usually aren’t ideal. The procedure often needs to be repeated. One option is to manage your child’s hernias with supportive trusses rather than surgery because of the risks of anesthesia and surgery.
  • Managing neurological complications. Problems associated with the buildup of fluid and tissue around the brain and spinal cord are difficult to address because of the inherent risks in treating these parts of the body.
    Your child’s doctor may recommend surgery to drain excess fluids or remove built-up tissue. If your child has seizures, your doctor may prescribe anticonvulsant medications.
  • Managing behavioral problems. If your child develops abnormal behavior as a result of Hunter syndrome, providing a safe home environment is one of the most important ways you can manage this challenge.
    Treating behavior problems with medications has had limited success because most medications have side effects that can make other complications of the disease, such as respiratory problems, even worse.
  • Addressing sleep issues. The sleep patterns of a child with Hunter syndrome become more and more disorganized. Medications including sedatives and especially melatonin can improve sleep.
    Keeping a strict bedtime schedule and making sure your child sleeps in a well-darkened room also can help. In addition, creating a safe environment in your child’s bedroom — putting the mattress on the floor, padding the walls, removing all hard furniture, placing only soft, safe toys in the room — may help you rest easier if you know your child has less opportunity for injury.

Emerging treatments

Some treatments that are in their early stages of development have had some success by slowing the disease’s progress and lessening its severity.

  • Enzyme therapy. This treatment uses man-made or genetically engineered enzymes to replace your child’s missing or defective enzymes and ease the disease symptoms. This treatment is given once a week through an intravenous (IV) line.
    Given early enough, enzyme replacement therapy may delay or prevent some of the symptoms of Hunter syndrome. It’s unclear, however, if the improvements seen with this therapy are significant enough to raise quality of life for people with the disease. In addition, benefits in thinking and intelligence haven’t been seen with enzyme replacement therapy.
    Serious allergic reactions can occur during enzyme replacement therapy. Other possible side effects include headache, fever, skin reactions and high blood pressure. Side effects tend to lessen over time, however.

Gene therapy. Replacing the chromosome responsible for producing the missing enzyme could theoretically cure Hunter syndrome, but much more research is needed before this therapy will be available.

Lifestyle changes & home remedies

What are some lifestyle changes or home remedies that can help me manage Hunter syndrome?

The following lifestyles and home remedies might help you cope with Hunter syndrome:

Letting others know

Due to a narrow airway, people with Hunter syndrome often have difficulty receiving a breathing tube (being intubated) during general anesthesia. You may wish to note this on child care or school forms so that emergency personnel can be alerted to this fact, in case your child has an emergency and you’re not there. An experienced anesthesia specialist (anesthesiologist) should perform the intubation of a person with Hunter syndrome.

Preparing for your appointment

You’ll probably first bring up your concerns about your child with his or her primary care doctor. Your child’s doctor then will likely direct you to specialists for a definitive diagnosis and treatment. However, your child’s primary care doctor generally still stays involved to help coordinate your child’s health care needs.

Some of the specialists that may be involved in your child’s care include an ear, nose and throat specialist (otolaryngologist), a heart specialist (cardiologist), a brain and nerve specialist (neurologist), an eye specialist (ophthalmologist), a dietitian, and physical, occupational and speech therapists. A geneticist may be involved in making the diagnosis and in counseling about future pregnancies.

Here’s some information to help you get ready for your appointment, and what you might expect from your child’s doctor.

What you can do

  • Make a list of any signs or symptoms you’ve noticed in your child, including any that may seem unrelated to Hunter syndrome. For example, diarrhea is a sign of Hunter syndrome, but one that you might not necessarily link to behavioral problems.
  • Write down key personal information, including any personal or family history of a genetic disorder.
  • Take a family member or friend along, if possible. Sometimes it can be difficult to remember all of the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
  • Write down questions to ask your doctor.

Preparing a list of questions will help you make sure you cover all of the points that are important to you. Some basic questions you might want to ask your doctor include:

  • What is Hunter syndrome?
  • Are there any other possible causes for my child’s symptoms?
  • Are any additional tests needed to confirm the diagnosis?
  • What treatments are available, and which ones do you recommend for my child?
  • Does this treatment have any risk?
  • What type of improvement can we expect?
  • What is my child’s long-term prognosis?
  • Are there alternatives to the primary approach that you’re suggesting?
  • Does my child need to eat a special diet?
  • If my child is in pain, how can I make my child more comfortable?
  • What are your suggestions for handling behavioral issues?
  • What about routine well-child care? Should my child get routine childhood immunizations? Should my child get flu shots?
  • Does my child need to see different specialists?
  • What type of help will my child need in school, and how can I ensure that public schools will provide the educational resources my child needs?
  • If I have any more children, what’s the likelihood that I will pass this syndrome on to them? Can I prevent that from happening?
  • Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting? Are there local resources available for me and my child?
  • Can you recommend someone I can speak with about insurance coverage and other expenses related to the special needs of my child?

In addition to the questions that you’ve prepared to ask your doctor, don’t hesitate to ask additional questions that occur to you during your appointment. If it helps, take notes.

At the end of your appointment, you may wish to summarize the information you’ve received with your doctor to make sure you understand it. Ask for a copy of your doctor’s clinical note for future reference and communication with other facilities.

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Sources

Review Date: January 30, 2018 | Last Modified: January 30, 2018

Want to live your best life?
Get the Hello Doktor Daily newsletter for health tips, wellness updates and more.