Alternative Names mucopolysaccharidosis II, sulpho-iduronate sulphatase deficiency
Definition Hunter syndrome is a genetic disorder that causes a protein called mucopolysaccharide to build up in body tissues. This damages the tissues and leads to the symptoms.
What is going on in the body? A person with Hunter syndrome lacks an enzyme known as sulphoiduronate sulphatase. When this enzyme is missing, mucopolysaccharides collect in body tissues, which causes damage.
What are the signs and symptoms of the disease? There are mild and severe types of Hunter syndrome.
The mild type, which usually isn't noticed until later in life, can cause:
The severe type of Hunter syndrome shows up in early childhood, and shortens the person's lifespan. It causes the same symptoms as the mild form, but they are more severe. In addition, a person with the severe form often has:
spasticity, or tight muscles that interfere with motor activities
hyperactivity, with constant movement and impulsive behaviour
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. Males who receive the gene from a parent are affected. Females who receive the gene from a parent are not affected and are called carriers. The syndrome can also occur because of a mutation in a parent's sperm or egg cell.
What can be done to prevent the disease? Hunter syndrome cannot be prevented once a child has been conceived. Genetic counselling may be helpful to couples with a family history of the disease.
How is the disease diagnosed? A doctor often suspects a person has Hunter syndrome based on his or her physical features. Enzyme studies confirm the diagnosis. Mucopolysaccharides and other proteins also can be measured in the urine to confirm diagnosis.
What are the long-term effects of the disease? A person with the mild type of Hunter syndrome develops heart disease and deafness. He or she may become immobile because of stiff joints, and develop degenerative hip disease.
A person with the severe type usually doesn't live past the second or third decade of life. By then, he or she will have mental retardation and joint stiffness.
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 counselling may be useful for affected people and their relatives.
What are the treatments for the disease? There is no specific treatment for Hunter syndrome. Medications may be used for problems caused by the syndrome, such as heart disease, joint stiffness, hearing impairment, or degenerative joint disease.
What are the side effects of the treatments? Side effects depend on the treatment given for the medical conditions caused by Hunter syndrome.
What happens after treatment for the disease? Hunter syndrome itself cannot be treated. Medical problems such as heart disease, degenerative joint disease, and hearing impairment can be treated, but will still affect the person's lifestyle.
How is the disease monitored? Hunter syndrome is monitored by regular visits to the doctor, and complications are dealt with as they arise. Any new or worsening symptoms should be reported to the doctor.
Author: James Broomfield, MD Reviewer: eknowhow Medical Review Panel Editor: Dr John Hearne Last Updated: 28/11/2004 Contributors Potential conflict of interest information for reviewers available on request
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