Hunter Syndrome

What is Hunter Syndrome?

Hunter Syndrome (also called mucopolysaccharidosis Type II or MPS II) is a very rare inherited, progressive and life threatening disease that primarily affects males. It is one of several related lysosomal storage diseases.

What are the signs and symptoms of Hunter Syndrome?

Hunter Syndrome has very variable symptoms and some sufferers can have a very severe and life-limiting disorder. Others however have a more mild disease course. It is usually diagnosed in childhood with sufferers having difficulties growing normally and with hearing, skin changes, frequent ear, nose and throat infections, joint problems, breathing difficulties, and in some patients progressive developmental delay.

What are the causes of Hunter Syndrome?

Hunter Syndrome is an inherited metabolic condition involving a deficiency or dysfunction in an enzyme (Iduronate-2-sulfatase [I2S]) within cells of the body. This problem means that certain types of sugar molecules (dermatan sulfate and heparan sulfate glycosaminoglycans or GAG) within the body are not correctly broken down and over time can build up and cause symptoms.

Who is likely to be at risk of Hunter Syndrome?

The chromosome pair that determines our gender contains either two X chromosomes for a female or an X and a Y chromosome for a male. Daughters (XX) inherit an X chromosome from their mother and an X chromosome from their father. The I2S gene is located on the X chromosome.

If a male has an abnormal copy of the I2S gene he will develop Hunter Syndrome. A male can obtain an abnormal copy of the I2S gene in one of two ways. His mother is often a carrier; i.e., she has one abnormal and one normal I2S gene, and she passes along the abnormal gene to him. However, during egg and sperm formation, a mutation can develop in the I2S gene on his X chromosome. In this second case, the mother is not a carrier and the risk of a spontaneous mutation occurring again in a future sibling is low but not zero. Females can carry one abnormal copy of the I2S gene and are usually not affected. Hunter syndrome has been reported to occur in females.

Hunter Syndrome affects approximately 1 in 162,000 lives births.

How is Hunter Syndrome diagnosed?

Patients typically have a normal appearance at birth, with the initial signs and symptoms emerging between 18 months and 4 years of age. Diagnosis is by detection of the enzyme deficiency. In the UK, Hunter Syndrome (along with other Lysosomal Storage Disorders) is usually diagnosed and managed at nationally designated specialist centres.

What are the treatments for Hunter Syndrome?

Treatment of Hunter Syndrome consists of two components; symptom management and replacement of the deficient enzyme with enzyme replacement therapy (ERT). There are a variety of ways to improve symptoms. Finding the right specialist with experience of treating children with special needs. Palliative and symptomatic treatments can help relieve pain and enhance general health. Staying informed of medical progress can give you insights into the latest advances in managing Hunter Syndrome. Patient organisations provide general information and support for families living with the disease.

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