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Causes
By Mayo Clinic staffHunter syndrome develops when a defective chromosome is inherited from the child's mother. Because of that defective chromosome, an enzyme that's needed to break down complex sugars called glycosaminoglycans is missing or malfunctioning.
The missing or malfunctioning enzyme is called iduronate-2-sulfatase.
In unaffected people, these enzymes are found in parts of the body's cells known as lysosomes. The lysosomes use enzymes to break down glycosaminoglycans, as part of the body's normal recycling and renewal process. In a person with Hunter syndrome or another form of MPS, these enzymes either are missing or don't work correctly.
Normally, the nutrients that are broken down by lysosomes help your body build bone, cartilage, tendons, corneas, skin and connective tissue, and the fluid that lubricates your joints.
When this enzyme isn't working properly, undigested glycosaminoglycans collect in the cells, blood and connective tissues, causing permanent and progressive damage. Hunter syndrome and other forms of MPS are sometimes called lysosomal storage diseases.
- Scarpa, et al. Mucopolysaccharidosis type II: European recommendations for the diagnosis and multidisciplinary management of a rare disease. Orphanet Journal of Rare Diseases. 2011;6:1.
- Martin R, et al. Recognition and diagnosis of mucopolysaccharidosis II (Hunter syndrome). Pediatrics. 2008;121:e377.
- Mucopolysaccharidoses fact sheet. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/mucopolysaccharidoses/detail_mucopolysaccharidoses.htm. Accessed Oct. 11, 2012.
- Kakkis E, et al. Complications and management of the mucopolysaccharidoses. http://www.uptodate.com/ index. Accessed Sept. 21, 2012.
- Muenzer J, et al. Multidisciplinary management of Hunter syndrome. Pediatrics. 2009;124:e1228.
- Da Silva EMK, et al. Enzyme replacement therapy with idursulfase for mucopolysaccharidosis type II (Hunter syndrome). Cochrane Database of Systematic Reviews. 2011; 9:CD008185. http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD008185.pub2/abstract. Accessed Oct. 1, 2012.
- Valayannopoulos V, et al. Therapy for the mucopolysaccharidoses. Rheumatology. 2011;50:v49.
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