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Hunter Syndrome

Alternate Names

  • mucopolysaccharidosis II
  • sulfo-iduronate sulfatase deficiency

Definition

Hunter syndrome is a genetic disorder that causes a proteins called glycosaminoglycans (GAGs) to build up in body tissues. This damages the tissues and leads to the symptoms of the disorder.

What is going on in the body?

A person with Hunter syndrome lacks an enzyme known as iduronate 2-sulfatase. When this enzyme is missing, GAGs collect in and damage body tissues.

Risks

What are the causes and risks of the disease?

Hunter syndrome is an X-linked recessive disease. This means that the gene that causes it is carried on the X chromosome.
Thus, a male who receives the gene from his mother will be affected. A female can receive the gene either from her father (who has the disease) or from her mother (a carrier). This female, in turn, becomes a carrier herself and can pass the gene to her children.
The syndrome can also occur because of a mutation in a parent's sperm or egg cell.

Prevention

What can be done to prevent the disease?

Genetic counseling may be helpful to couples with a family history of the disease.

Diagnosed

How is the disease diagnosed?

A healthcare professional often suspects a person has Hunter syndrome based on his or her physical features. The diagnosis is confirmed either with enzyme studies or by measuring GAGs and other proteins in the urine.

Long Term Effects

What are the long-term effects of the disease?

A person with the mild type of Hunter syndrome develops heart disease and deafness, may become immobile because of stiff joints, and may develop degenerative hip disease. A person with the severe type usually does not live past the second or third decade after birth. By then, he or she will have mental retardation and joint stiffness.

Other Risks

What are the risks to others?

Hunter syndrome is not contagious.
A male with Hunter syndrome must pass on the gene to his daughters. However, they are not affected. An affected male cannot pass on the gene to his sons.
A carrier female may pass on the gene to her sons or daughters. Her sons who get the gene will be affected. Her daughters who get the gene will be carriers like her.
Genetic counseling may be useful for affected people and their relatives.

Treatments

What are the treatments for the disease?

Enzyme replacement therapy may soon be available for this condition. Medications may be used for problems caused by the syndrome, such as heart disease, joint stiffness, hearing impairment, or degenerative joint disease.

Side Effects

What are the side effects of the treatments?

Side effects depend on the treatment given.

After Treatment

What happens after treatment for the disease?

Medical problems such as heart disease, degenerative joint disease, and hearing impairment can be treated, but will still affect the person's lifestyle.

Monitor

How is the disease monitored?

Hunter syndrome is monitored by regular visits to the healthcare professional, and complications are dealt with as they arise. Any new or worsening symptoms should be reported to the healthcare professional.

Sources

Scriver CR et al: The Metobolic and Molecular Basis of Inherited Disease. McGraw-Hill Publishers, 1995

Buyse ML: Birth Defects Encyclopedia. Blackwell Scientific Publications, 1990

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