Synonyms

• MPS Disorder II
• MPS II
• Mucopolysaccharidosis Type II

Disorder Subdivisions

• MPS IIA
• MPS IIB

General Discussion

Hunter syndrome, also known as mucopolysaccharidosis II, is a rare inborn error of metabolism characterized by inadequate production of an enzyme known as iduronate sulfatase, which is needed to break down complex sugars produced in the body. Symptoms include growth delay, joint stiffness, and coarsening of facial features. In severe cases, patients experience respiratory and cardiac problems, enlargement of the liver and spleen, and neurological deficits. The disorder can lead to premature death in severe cases.

Hunter syndrome is one of a group of hereditary metabolic diseases known as the mucopolysaccharidoses (MPS), which in turn are part of a group known as lysosomal storage disorders. Lysosomes function as the primary digestive units within cells. Enzymes within lysosomes break down or digest particular nutrients, such as certain carbohydrates and fats. In individuals with MPS disorders, including Hunter syndrome, deficiency or improper functioning of lysosomal enzymes leads to an abnormal accumulation of certain complex carbohydrates in cells within various tissues, such as the skeleton, joints, brain, spinal cord, heart, spleen, or liver.

Initial symptoms and findings associated with Hunter syndrome usually become apparent in children from two to four years of age. Such abnormalities may include progressive growth delays, resulting in short stature; joint stiffness, with associated restriction of movements; and coarsening of facial features, including thickening of the lips, tongue, and nostrils. Affected children may also have an abnormally large head (macrocephaly), a short neck and broad chest, delayed tooth eruption, progressive hearing loss, and enlargement of the liver and spleen (hepatosplenomegaly). Two relatively distinct clinical forms of Hunter syndrome have been recognized. In the late-onset, mild form of the disease (MPS IIB), intelligence may be normal or only slightly impaired. However, in the early-onset, more severe form (MPS IIA), profound mental retardation may be apparent by late childhood. In addition, slower disease progression tends to occur in those with the mild form of the disorder.

Hunter syndrome is inherited as an X-linked recessive trait. Mild and severe forms of the disorder result from changes (mutations) of a gene (i.e., IDS gene) that regulates production of the iduronate sulfatase enzyme. The IDS gene is located on the long arm (q) of chromosome X (Xq28).

Resources

CLIMB (Children Living with Inherited Metabolic Diseases)
Climb Building
176 Nantwich Road
Crewe, Intl CW2 6BG
United Kingdom
Tel: +44 870 7700 325
Fax: +44 870 7700 327
Email: info@climb.org.uk
Internet: http://www.CLIMB.org.uk

Vaincre Les Maladies Lysosomales
2 ter avenue de Fance
Massy, 91300
France
Tel: 01 69 75 40 30
Fax: 01 60 11 15 83
Email: accueil@vml-asso.org
Internet: http://www.vml-asso.org

March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: (914)428-7100
Fax: (914)997-4763
Tel: (888)663-4637
Email: Askus@marchofdimes.com
Internet: http://www.marchofdimes.com

The Arc (a national organization on mental retardation)
1010 Wayne Ave
Suite 650
Silver Spring, MD 20910
Tel: (301)565-3842
Fax: (301)565-3843
Tel: (800)433-5255
TDD: (817)277-0553
Email: info@thearc.org
Internet: http://www.thearc.org/

National MPS (Mucopolysaccharidoses/Mucolipidoses) Society, Inc.
PO Box 736
Bangor, ME 04402-0736
Tel: (207)947-1445
Fax: (207)990-3074
Email: info@mpssociety.org
Internet: http://www.mpssociety.org

NIH/National Institute of Diabetes, Digestive & Kidney Diseases
Endocrine Diseases Metabolic Diseases Branch
2 Information Way
Bethesda, MD 20892-3570
Tel: (301)654-3810
Fax: (301)496-7422
Email: NDDIC@info.niddk.nih.gov
Internet: http://www.niddk.nih.gov

Society for Mucopolysaccharide Diseases
46 Woodside Road
Amersham
Buckinghamshire, HP6 6AJ
United Kingdom
Tel: 004401494 434156
Fax: 004401494 434252
Email: mps@mpssociety.co.uk
Internet: http://www.mpssociety.co.uk

Canadian Society for Mucopolysaccharide and Related Diseases, Inc.
PO Box 64714
Unionville
Ontario, Intl L3R OM9
Canada
Tel: 905-479-8701
Fax: 905-479-8701
Tel: 800-667-1846
Email: lori.mps@rogers.com
Internet: http://www.mpssociety.ca

MUMS (Mothers United for Moral Support, Inc) National Parent-to-Parent Network
150 Custer Court
Green Bay, WI 54301-1243
USA
Tel: 9203365333
Fax: 9203390995
Tel: 8773365333
Email: mums@netnet.net
Internet: http://www.netnet.net/mums/

Let Them Hear Foundation
1900 University Ave #101
East Palo Alto, CA 94303
Tel: (650)462-3143
Fax: (650)462-3143
Tel: (877)735-2929
Email: info@letthemhear.org
Internet: http://www.letthemhear.org

Hide & Seek Foundation for Lysosomal Disease Research
4123 Lankershim Blvd.
Suite 302
North Hollywood, CA 91602-2828
Tel: (818)762-8621
Fax: (818)762-2502
Email: info@hideandseek.org
Internet: http://www.hideandseek.org

For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc. ® (NORD). A copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report.

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site www.rarediseases.org or email orphan@rarediseases.org

Last Updated:  8/17/2007
Copyright  1986, 1987, 1988, 1990, 1999, 2000, 2001, 2002, 2004, 2006, 2007National Organization for Rare Disorders, Inc.