Definition: Hunter syndrome is an inherited disease in which long chains of sugar molecules (mucopolysaccharides ) are not broken down correctly and build up in the body.
Alternative Names: Mucopolysaccharidosis type II, Iduronate sulfatase deficiency
Causes, incidence, and risk factors: Hunter syndrome is an inherited condition. Boys are most often affected. The condition is caused by a lack of the enzyme iduronate sulfatase. Without this enzyme, mucopolysaccharides build up in various body tissues, causing damage. The early-onset, severe form of the disease begins shortly after age 2. A late-onset, mild form causes less severe symptoms to appear later in life.
Symptoms: Juvenile form (early-onset, severe form): Late (mild) form: - Mild to no mental deficiency
Both forms:
Signs and tests: Signs of the disorder include: Tests may include: - Enzyme study
- Genetic testing for change (mutation) in the iduronate sulfatase gene
- Urine test for heparan sulfate and dermatan sulfate
Treatment: The U.S. Food and Drug Administration has approved the first treatment for Hunter syndrome. The medicine, called idursulfase (Elaprase), is given through a vein (intravenously). Talk to your doctor for more information. Bone marrow transplant has been tried for the early-onset form, but the results can vary. Each health problem should be treated separately.
Expectations (prognosis): People with the early-onset (severe) form usually live for 10 - 20 years. People with the late-onset (mild) form usually live 20 - 60 years.
Complications: - Airway obstruction
- Carpal tunnel syndrome
- Hearing loss that gets worse over time
- Loss of ability to complete daily living activities
- Joint stiffness that leads to contractures
- Mental function that gets worse over time
Calling your health care provider: Call your health care provider if: - You or your child has a group of these symptoms
- You know you are a genetic carrier and are considering having children
Prevention: Genetic counseling is recommended for couples who want to have children and who have a family history of Hunter syndrome. Prenatal testing is available. Carrier testing for female relatives of affected males is available at a few centers.
References: Muenzer J, Wraith JE, Beck M, et al. A phase II/III clinical study of enzyme replacement therapy with idursulfase in mucopolysaccharidosis II (Hunter syndrome). Genet Med. 2006 Aug;8(8):465-73. Wraith JE. Mucopolysaccharidoses and oligosaccharidoses. In: Fernandes J, Saudubray J-m, van den Berghe G, Walter JH, eds. Inborn Metabolic Diseases: Diagnosis and Treatment. New York, NY: Springer;2006:chap 39.
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