Hunter syndrome is a rare genetic disorder that occurs when an enzyme your body needs is either missing or malfunctioning.
Because the body doesn't have adequate supplies of the enzyme to break down certain complex molecules, the molecules build up in harmful amounts in certain cells and tissues. The buildup that occurs in Hunter syndrome eventually causes permanent, progressive damage affecting appearance, mental development, organ function and physical abilities.
Hunter syndrome appears in children as young as age 2. It nearly always occurs in males.
There's no cure for Hunter syndrome. Treatment of Hunter syndrome involves management of symptoms and complications.
Hunter syndrome is one type of a group of inherited metabolic disorders called mucopolysaccharidosis (MPS), and Hunter syndrome is referred to as MPS II. There are two subtypes of Hunter syndrome, MPS IIA and MPS IIB. Symptoms vary according to subtype.
Type MPS IIA (early onset)
Signs and symptoms of MPS IIA include:
Type MPS IIB (late onset)
Signs and symptoms of MPS IIB include:
When to see a doctor
Hunter syndrome occurs when an enzyme that's needed to break down complex sugars called glycosaminoglycans is missing or malfunctioning.
In unaffected people, these enzymes are found in parts of the body's cells known as lysosomes. The lysosomes use enzymes to break down glycosaminoglycans, as part of the body's normal recycling and renewal process. In a person with Hunter syndrome or another form of MPS, these enzymes either are missing or don't work correctly.
Normally, the nutrients that are broken down by lysosomes help your body build bone, cartilage, tendons, corneas, skin and connective tissue, and the fluid that lubricates your joints.
When this enzyme isn't working properly, undigested glycosaminoglycans collect in the cells, blood and connective tissues, causing permanent and progressive damage. Hunter syndrome and other forms of MPS are sometimes called lysosomal storage disorders.
In the case of Hunter syndrome, the missing or malfunctioning enzyme is called iduronate-2-sulfatase.
Hunter syndrome develops when a defective chromosome is inherited from the child's mother.
There are two major risk factors for developing Hunter syndrome:
X-linked recessive inheritance pattern with carrier mother
A woman who is a carrier of an X-linked recessive disorder has a 25 percent chance of having an unaffected son, a 25 percent chance of having an affected son, a 25 percent chance of having an ...
A variety of complications can occur with Hunter syndrome depending on the type and severity of the disease. These may include:
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. 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.
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
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:
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask additional questions during your appointment. Don't hesitate to 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.
What to expect from your doctor
Tests and diagnosis
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.
To confirm the diagnosis of Hunter syndrome, your doctor will perform blood, urine or tissue sample tests that look for excess glycosaminoglycans in your child's urine or a deficiency of enzymes in your child's body fluids or cells. In addition, a genetic analysis can confirm the diagnosis.
Sometimes another health issue can lead to a diagnosis of Hunter syndrome. For example, if your child has recurrent pneumonia, a chest X-ray may show irregularly shaped vertebrae and ribs, a common sign of this syndrome. This finding could lead to further testing and an earlier diagnosis of the disease. However, because the disorder progresses slowly and its signs and symptoms overlap with a number of other disorders, definitive diagnosis may take some time.
Treatments and drugs
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.
These emerging treatments include:
Treatments for complications
Coping and support
Support for you and your family
The intense supervision that may be needed for your child can cause you and other caregivers to become physically, mentally and emotionally exhausted. It's important to get help from other family members and to find other kinds of support.
If respite care is available, take advantage of it so that you can have a break and be more effective in the long run to meet the day-to-day challenges of caring for a child with special needs.
Letting others know
Check with your county and state for resources that may be available to you as a parent of a child with special needs.
Hunter syndrome is a genetic disorder. Talk to your doctor or a genetic counselor if you're thinking about having children and you or any members of your family have a genetic disorder or a family history of genetic disorders. If you think you might be a carrier, genetic tests are available. If you already have a child with Hunter syndrome, you may wish to seek the advice of a doctor or genetic counselor before you have more children.
Last Updated: 2010-08-10
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