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Hunter syndrome


Definition:

Hunter syndrome is a disease in which long chains of sugar molecules (glycosaminoglycans, formerly called mucopolysaccharides) are not broken down correctly and build up in the body.

The syndrome belongs to a group of diseases called mucopolysaccharidoses (MPS). Specifically, it is known as MPS II.

See also:

Alternative Names:

Mucopolysaccharidosis type II; Iduronate sulfatase deficiency

Causes:

Hunter syndrome is an inherited condition, which means it is passed down through families. The affected gene is on the X chromosome. Therefore, boys are most often affected. Their mothers do not have symptoms of the disease, but they carry a nonworking copy of the gene.

The condition is caused by a lack of the enzyme iduronate sulfatase. Without this enzyme, chains of sugar molecules 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:

In the early-onset, severe form, symptoms include:

In the late (mild) form, there can be mild to no mental deficiency.

In both forms, symptoms include:

Exams and Tests:

A physical exam and tests in someone with Hunter syndrome may show:

Tests may include:

  • Enzyme study
  • Genetic testing for a change in the iduronate sulfatase gene
  • Urine test for heparan sulfate and dermatan sulfate
Treatment:

The U.S. Food and Drug Administration (FDA) has approved the first treatment for Hunter syndrome. The medicine, called idursulfase (Elaprase), is given through a vein (IV, intravenously). Talk to your health care provider for more information.

Bone marrow transplant has been tried for the early-onset form, but the results can vary.

Each health problem caused by this disease should be treated separately.

Outlook (Prognosis):

People with the early-onset (severe) form usually live for 10 to 20 years. People with the late-onset (mild) form usually live 20 to 60 years.

Possible Complications:

These complications may occur:

  • 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
When to Contact a Medical Professional:

Call your 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:

Ma, C, Ali S, Dorshi N, Dominguez R. Storage diseases. In: Pope TL, Bloem HL, Beltran J, Morrison WB, eds. Musculoskeletal Imaging. 2nd ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 82.

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.

Pyeritz RE. Inherited diseases of connective tissue. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 260.

Wraith JE. Mucopolysaccharidoses and oligosaccharidoses. In: Saudubray JM, van den Berghe G, Walter JH, eds. Inborn Metabolic Diseases: Diagnosis and Treatment. 5th ed. New York, NY: Springer; 2012:chap 40.


Review Date: 4/20/2015
Reviewed By: Chad Haldeman-Englert, MD, FACMG, 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, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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