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Hunter syndrome, or mucopolysaccharidosis II (MPS II), is a rare genetic disorder that primarily affects males. It is one of several related lysosomal storage disorders (LSDs). A child may not show any signs of Hunter syndrome until after the first years of life. However, signs become increasingly visible as the child ages.
In people with Hunter syndrome, an important enzyme called iduronate-2-sulfatase (I2S) is either partially missing or completely inactive. Without I2S, the body is unable to break down and recycle sugar-like molecules in the body called glycosaminoglycans, or GAGs. As a result, GAGs build up in cells throughout the body.
Hunter syndrome is genetic, meaning it is passed down through families. Though females aren’t typically affected by the disease, they can be carriers and pass a defective chromosome to a child. A spontaneous mutation can also occur during egg and sperm formation, so the condition isn’t always passed on from the mother.
Although Hunter syndrome is a progressive disease, symptoms can vary greatly from person to person. Patients typically appear normal at birth, with changes in facial features becoming apparent at 2 to 4 years of age. Patients tend to be tall for their age until about 4 to 5 years of age. Mobility is restricted because of joint stiffness and bone changes. Ear infections and upper respiratory infections are common. Surgery for inguinal or umbilical hernias is common. Since these are common symptoms, doctors aren't likely to always diagnose Hunter syndrome right away.
The visible signs and symptoms of Hunter syndrome in younger people are usually the first clues leading to a diagnosis. In general, diagnosis usually occurs when patients are between 2 and 4 years of age.
Several tests may provide additional evidence that the disorder is present, but the only way to make a definitive diagnosis is to measure iduronate-2-sulfatase (I2S) enzyme activity. This test can even help determine clinical severity in some people. Prenatal diagnosis is possible by measuring I2S enzymatic activity in amniotic fluid or tissues.
If you, your child or another loved one has been diagnosed with Hunter syndrome, please know that you’re not alone. Talking with other people who understand what you’re going through from firsthand experience can be a wonderful way to learn and begin building your support network.
Takeda provides funding to some of the below organizations in support of efforts that include, but are not limited to: research, education, meetings/events and support.
This organization provides hope and support for individuals and families affected by MPS and ML through research, advocacy and awareness. Browse MPS resources, apply for family support programs or get involved in fundraising.
A rare disease umbrella organization that provides advocacy, research, education and patient services in the US. See how they help and find out how you can get involved.