Hunter Syndrome

MPS ll
Sharah & Shadie

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Hunter syndrome is named after Charles A. Hunter, who was the first person to acknowledge and describe the disease in 1917. Hunter Syndrome is a rare genetic disorder that happens when the lysosomal enzyme (I2S) that your body needs is missing or is not working properly. This is a rare condition affecting 1 in 100,000 to 1 in 150,000 males. There is an estimate in the United States that 1 in 25,000 births will result in some form of MPS. Hunter syndrome is divided into severe and mild classifications.
Some symptoms that come from Hunters Syndrome are :
  • Decline in development skills
  • Mental retardation
  • Thickening of lips, tongue, and nostrils
  • Abnormal bone size and irregular skeletal structures
  • Respiratory problems
  • Vision loss
  • Joint stiffness
  • Diarrhea along with cold symptoms

Hunter's Syndrome is an inherited disease. The onset of the disease usually happens around the age of 2. The carrier of the disease will experience a slow decline of skills needed for everyday life. There has not been a total cure for the disease yet.

Biology of the disease

In the human body we rely on many biochemical reactions to break down large biomolecules, make energy, growth and development, and protection from infection. The human cells contain an outside layer called the extracellular matrix (EM), this is a issue that makes up the framework and holds together the cells in the body. The EM is made of sugars and proteins. Proteoglycan is a part of the EM, that needs to be broken down and replaced by new ones.When the body breaks down proteoglycans, one of the resulting products is mucopolysaccharides, otherwise known as GAG. Inside the GAG are derman and herapan sulfate. The breakdown of dermatan sulfate and heparan sulfate requires the lysosomal enzyme I2S. Hunter syndrome leaves the carrier without the I2S enzyme so the EM cannot be broken down. This creates a buildup of GAG in the cells throughout the body. Organs become dysfunctional and they swell.

Iduronate Sulfatase

Iduronate sulfatase is an enzyme that specifically cleaves the ester sulfate of iudonic acid. It is required for the defulsation of 2-sulfate iduronate residues in herapan sulfate. It is also required in derman sulfate degradation.

Who Does it Affect?

The majority of people affected by MPS ll or Hunters Syndrome are males. The reasoning behind this lies within the chromosomes. If the male in question inherits an abnormal copy of the I2S gene, his genes will then be mutated causing him to have Hunter Syndrome. There are two ways to receive the mutated I2S gene:
  1. From the mother. The mother can be a carrier of the mutated I2S gene and not be aware because she will show no symptoms.
  2. The mutation can be spontaneous and occur for no apparent reason.

The IDS gene is located on the long (q) arm of the X chromosome at position 28.
The IDS gene is located on the long (q) arm of the X chromosome at position 28.

As you can see in the picture above the I2S gene is located between base pair 148,560,294 to base pair 148,586,883 on the X chromosome. You could also call this position 28.
Early Signs

Types of confirmation tests

  • Enzyme study
  • Genetic testing for change (mutation) in the iduronate sulfatase gene
  • Urine test for heparan sulfate and dermatan sulfate

Types of treatments

  1. Enzyme replacement therapy
    • Medical treatment to replace the missing enzymes
    • Done by giving IV injections
    • This does NOT treat the disease: it cures symptoms
  2. Bone Marrow Graft
    • Stops all symptoms except for ones occurring in the brain
    • This translates in much improved life expectancy
    • One marrow graft is a major surgical operation with several adverse effects of such surgery
    • Life threatening
  3. Palliative treatment
    • Used to reduce the effects of deterioration
    • Surgery and psychiatry are often pivotal here
  4. Elaprase
    • Synthetic version of I2S
    • A purified form of the lysosomal enzyme iduronate-2-sulfatase and is produced by recombinant DNA technology in a human cell line
    • One of the most expensive drugs ever produced, with an estimated cost of $300,000 per patient, per year

Is this preventable?

Hunters syndrome is not extremely preventable. The best advice given to prevent giving birth to a child with this syndrome is to go to genetic counseling.

Hunter's Disease
Hunter's Disease


Hunters Syndrome : True Story

Check It Out!

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