What is Hunter syndrome?

Because Hunter syndrome is a rare, inherited disorder that mostly impacts children, it can lead to many questions from the parents and caregivers of those that are affected.

For many, it can be helpful to gain a better understanding of Hunter syndrome, its symptoms, and options such as clinical trials that are available to patients, which is why we’ve assembled a brief overview below.

What is Hunter syndrome?

Hunter syndrome is a type of mucopolysaccharidoses metabolic disorder (MPS), also known as MPS II. It is a genetic, inherited condition caused by an absence or malfunction of the enzyme iduronate 2-sulfatase. This enzyme is essential to breaking down certain complex sugar molecules, and without it, these molecules build up in harmful amounts.

This molecular buildup manifests in the cells, blood, and connective tissue of the body, eventually leading to permanent, progressive damage. The buildup can have an impact on a child’s appearance, mental development, physical abilities, and organ function.

Common Hunter syndrome symptoms

Typically, children born with Hunter syndrome do not have symptoms at birth, but signs of the disease will begin to emerge between the ages of two and four. Symptoms are progressive but manifest and develop differently in every patient. Some of the common Hunter syndrome symptoms include:

  • An enlarged head and fluid accumulation around the brain
  • Broadening of the lips and nose
  • Skeletal irregularities and joint stiffness
  • Delayed development, walking, and talking

What chromosome is affected by Hunter syndrome?

Hunter syndrome is more common in boys than girls due to how it impacts the X chromosome. The condition is caused by a variation in the IDS gene, and because males only have one X chromosome, a single IDS variation is enough for the syndrome to manifest. Because female babies have two X chromosomes, a variation of the IDS gene must be present in both to cause the disease. 

Treatment and Hunter syndrome life expectancy

Because each case is unique, treatment plans for those diagnosed with Hunter syndrome are highly specific to patients and can include enzyme replacement therapy in addition to targeted symptom management. The severity of Hunter syndrome symptoms can vary, as can a patient’s life expectancy. A severe diagnosis typically results in a 10- to 20-year lifespan, while those with a milder diagnosis will usually live further into adulthood.

Currently, Hunter syndrome has no known cure — which is why clinical trials can be so important to improving the lives of future patients. As researchers learn more about this condition via medical studies, new treatments and therapies will have an opportunity to emerge. If you are caring for someone with Hunter syndrome, use the tool below to check for available clinical trials.