Mucopolysaccharidosis, or Hunter syndrome, is a rare genetic disorder that affects mostly males. It occurs when the enzyme needed to break down complex sugars (called the iduronate-2-sulfatase enzyme) is missing or not working correctly.
With Hunter syndrome, chains of sugar molecules (called mucopolysaccharides) can't be broken down. They accumulate in the body, which harms cells and tissues.
Hunter syndrome, which isn't present at birth, can be either severe or mild. The severe form begins just after age 2, while symptoms of the mild form don't start until later.
Most people with Hunter syndrome will have a larger than normal head; facial features that include a broad nose, flared nostrils, and thickening of the lips, tongue, and nostrils; deafness that worsens over time; joint stiffness; and carpal tunnel syndrome.
The juvenile (severe) form of Hunter syndrome includes aggressive behavior, hyperactivity, severe intellectual disability, and stiff or rigid muscles.
Other signs and symptoms include cardiovascular problems, vision disturbances, enlarged spleen or liver, hernias, and respiratory difficulties.
There is no cure for Hunter syndrome but the U.S. Food and Drug Administration (FDA) has approved the drug idursulfase (Elaprase) to help lessen symptoms. Bone marrow transplants can effectively slow the progression of the disease in some who have it.
People with a family history of Hunter syndrome who are thinking about having children should seek genetic counseling.
All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.
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