Definition:
Hunter/MPS II is caused by the mutated gene that manufactures the enzyme iduronate sulfatase. This enzyme, needed to break down sugars known as mucopolysaccharides, is either produced in very low amounts or is completely absent in individuals afflicted with this disorder. The sugars are used to build tissues, cartilage, skin, tendons, and joint fluid in the body. Individuals affected with Hunter/MPS II have too many mucopolysaccharides in their system. An excessive amount of mucopolysaccharides results in the clinical symptoms of Hunter/MPS II.

There are two different types of Hunter/MPS II, classified by their age of onset and the severity of the symptoms: The early onset type is characterized by more severe symptoms and the late-onset form is characterized by more mild symptoms.

Hunter/MPS II is estimated to affect one in 100,000 to 150,000 births worldwide.

Symptoms:
Symptoms of both forms of this disorder include coarse facial features, a large head, stiff joints, hearing loss, increased hair production, enlarged liver and spleen, and carpel tunnel syndrome. The early onset form of Hunter/MPS II manifests shortly after two years of age. Symptoms include those that are general to each of the forms, as well as mental deterioration, mental retardation, aggression, and hyperactivity.

The late-onset form of Hunter/MPS II includes those symptoms that are general to each of the forms, as well as mental deterioration.

Inheritance Pattern:
Hunter/MPS II is an X-linked recessive disorder.

Life Expectancy:
Life expectancy for early-onset Hunter/MPS II is younger than 20 years of age.
Life expectancy for the late-onset form is between 20 and 60 years of age.

Diagnosis and Testing:
A urine test is able to measure increased levels of mucopolysaccharides, the type of sugar chain in the lysosome that accumulates as a result of the malfunctioning enzyme. A urine test is routinely followed by a blood test or skin biopsy, which will reveal reduced activity of the enzyme iduronate sulfatase. Prenatal screening is available to examine iduronate sulfatase activity in the fetus. Genetic testing is also available in combination with these diagnostic tests to look for the mutation that causes Hunter/MPS II.

Treatment:
In 2006, the FDA approved the first drug to treat this disorder. Elaprase is an enzyme replacement therapy designed to arrest or halt the disorder’s progress.

Other forms of treatment involve reducing some of the symptoms that are associated with this disorder. Such treatments include enlisting the support of a breathing device to improve upper airway obstructions. Physical therapy can alleviate the muscle and joint stiffness associated with this disorder. Surgery may also be necessary for a hernia, spinal cord compression, carpel tunnel syndrome, and/or heart valve replacement. Anticonvulsant medication may also be prescribed as well as medication to improve sleep.

Bone marrow transplantation has show variable results in individuals with the early-onset form of Hunter/MPS II.

Patient Groups:
National MPS Society
4220 NC Highway 55, Suite 140
Durham NC, 27713
www.mpssociety.org
tel: (919) 806-0101
fax: (919) 806-2005
Barbara Wedehase, Executive Director
info@mpssociety.org