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A.D.A.M. Medical Encyclopedia. Atlanta (GA): A.D.A.M.; 2011.

A.D.A.M. Medical Encyclopedia.

Hunter syndrome

Mucopolysaccharidosis type II, Iduronate sulfatase deficiency

Last reviewed: May 16, 2011.

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.

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

  1. 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. [PubMed: 16912578]
  2. 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.

Review Date: 5/16/2011.

Reviewed by: Chad Haldeman-Englert, MD, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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What works?

  • Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome) Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome)
    Hunter syndrome or mucopolysaccharidosis II is a rare genetic disease that occurs when an enzyme that the body needs is either missing or malfunctioning. The body doesn't have adequate supplies of this enzyme to break down certain complex molecules, so these molecules build up in harmful amounts in certain cells and tissues. The build‐up 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 the age of two years and it nearly always occurs in males. In the past, treatment of Hunter syndrome has been limited to the relief of symptoms and complications. Enzyme replacement therapy with idursulfase aims to replace iduronate‐2‐sulfatase, the enzyme that is deficient or absent in people with Hunter syndrome. However, given its high cost it is essential to assess how effective and safe this treatment is. Current evidence is limited because there was only one randomised clinical trial found in the medical literature. Compared with placebo, enzyme replacement therapy with idursulfase in people with Hunter syndrome, led to some improvement in the patients' ability to walk and a reduction in the excretion of  abnormal mucopolysaccharides in the urine. To date there is no evidence available in the literature showing that treatment reduces complications of the disease related to quality of life and mortality.
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