Mucopolysaccharidosis type II; Iduronate sulfatase deficiency
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.
In the early-onset, severe form, symptoms include:
Genetic testing for a change in the iduronate sulfatase gene
Urine test for heparan sulfate and dermatan sulfate
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.
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
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.
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. PMID: 16912578 www.ncbi.nlm.nih.gov/pubmed/16912578.
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.
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.