Hunter Syndrome

Hunter Syndrome

By: Malik Pierce

Info

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Info

Treatments

Complications Associated with Disease

Symptoms

References:

• Savitha N S et al
• Caio Perez Gomes et al
• S. Al Sawaf et al
• Barbara K. Burton et al
• M. Rathmann et al
• Roberto Giugliani

Normal Hand vs. Hunter Syndrome Hand

Mucopolysaccharides Type ll

Lysosome is an membrane bound organelle found in this disease that contains digestive enzymes. They break down excess or worn-out cell parts.

Hunter syndrome is caused by a defective chromosome, and a child must inherit the defective chromosome to develop the disease. Hunter syndrome is what's known as an X-linked recessive disease, which means that women carry the defective disease-causing X chromosome and can pass it on. There are two forms of Hunter's syndrome based on the length of survival and the presence or absence of central nervous system (CNS) involvement. Type A is the most severe form with a life expectancy of 14-15 years and a much earlier onset. Type B is a much milder form with a life expectancy of 30-50 years and physical features similar to, but not as severe as those of Type A.

The IDS gene is located on the Xq28 chromosome and 640 mutations related to Hunter Syndrome are reported on the Human Gene Mutation Database (HGMD). From the mutations described, 323 are missense or nonsense, 59 splicing substitutions, 119 small deletions, 49 small insertions/duplications, 14 small indels, 52 gross deletions, 4 gross insertions/duplications, and 20 complex rearrangements

Signs and symptoms of both types of Hunter syndrome typically begin to appear in children between ages 2 and 4. Hunter syndrome symptoms vary in severity and include:

• Stiff joints
• Thickening of facial features including nostrils, lips and tongue
• Delayed appearance of teeth or wide spaces between teeth
• Larger than normal head, wide chest and short neck
• Hearing loss that gets worse with time
• Delayed growth, especially starting around age 5
• Enlarged spleen and liver
• White growths on the skin

Doctors classify Hunter syndrome into severe and mild types. The severe type progresses faster and involves impaired intellectual abilities. In the most severe cases, people begin to experience problems with basic functioning around ages 6 to 8. Depending on its severity, Hunter syndrome can involve many complications. Doctors use medications and sometimes surgery to manage these complications. They include:

• Breathing problems due to thickened tissue and blocked airways
• Heart disease
• Joint and bone abnormalities
• Declining brain function
• Carpal Tunnel Syndrome
• Hernias
• Seizures
• Behavioral problems

Treatment for Hunter syndrome depends on the symptoms. A team approach, with specialists in different areas of expertise, could help manage the potential problems associated with the condition and give patients the best possible care. The goal of treatment is to slow the progression of the disease and improve quality of life. The treatment shown to do this best is enzyme replacement therapy. Doctors replace the missing enzyme with a human-made version of the enzyme, called Elaprase®. Doctors usually deliver this treatment intravenously (through a needle inserted into the vein) once a week.

It occurs almost exclusively in males and currently affects approximately 500 boys in the U.S.

This is a rare condition affecting 1 in 100,000 to 1 in 170,000 primarily males.

Hunter syndrome, or mucopolysaccharidosis II, is an X-linked, progressive lysosomal storage disease in which patients are deficient in the lysosomal enzyme iduronate-2-sulfatase (I2S),1,2 which results in cellular accumulation of the glycosaminoglycans dermatan and heparan sulfate.