Hunter vs. Hurler syndrome: Similarities and differences

Hunter syndrome and Hurler syndrome are similar conditions with similar names — and as such, they are often confused. Both Hunter syndrome and Hurler syndrome are a result of genetic mutations that cause a build-up of toxins within the cells, and both result in similar symptoms. However, these conditions have different causes that are important to note. 

What to know about Hunter syndrome

What is Hunter syndrome?

Hunter syndrome (also known as MPS II) is one type of mucopolysaccharidoses (MPSs), a group of inherited metabolic disorders. It is a rare genetic disorder that is inherited from a child’s mother. Hunter syndrome occurs when the body does not have adequate amounts of the iduronate 2-sulfatase enzyme, which inhibits the body from breaking down certain complex molecules. When these molecules build up, they become harmful and result in progressive and permanent damage.

What causes Hunter syndrome?

Hunter syndrome is known as an X-linked recessive disease, which means it is a condition passed on to children from their mothers — but because Hunter syndrome primarily impacts males, most women do not know that they are carriers. 

How is Hunter syndrome diagnosed?

Children born with Hunter syndrome typically don’t have any symptoms — Hunter syndrome symptoms will typically begin between the ages of 2 and 4 due to the buildup of harmful molecules. The symptoms can include:

  • An enlarged head with skeletal irregularities
  • Thickening of the lips and a protruding tongue
  • A broad nose and flared nostrils
  • A deep, hoarse voice
  • Delayed development and stunted growth

If parents notice these symptoms, it is important to talk to their child’s doctor quickly to decide if further testing or evaluation is necessary. The Hunter syndrome life expectancy can range from 10 to 20 years in extreme cases, while individuals with milder cases have been known to live much longer.

What to know about Hurler syndrome

What is Hurler syndrome?

Hurler syndrome is a rare, severe form of mucopolysaccharidosis type 1 (MPS I). It is a lysosomal storage condition where the cells do not have enough enzymes to break down sugar molecules, which accumulate in lysosomes. Because lysosomes are the part of the cell in control of waste management, the buildup of toxins causes the cells to underperform or die quickly.

What causes Hurler syndrome?

Hurler syndrome is caused by a mutation to the IDUA gene that can occur at random, but parents with a history of MPS I in their families are at an increased risk of having a child with the condition. It impacts males and females equally and is considered rare, with roughly 1 in every 100,000 babies born with the condition.

How is Hurler syndrome diagnosed?

Prenatal screening tests can be done while a mother is pregnant to check for genetic abnormalities, but most children are diagnosed with Hurler syndrome after the first few years of life. Symptoms of Hurler syndrome begin early in childhood and continue through adolescence. Symptoms can include:

  • Heart valve problems
  • Hearing and vision loss
  • Fluid buildup around the brain
  • Enlarged organs
  • Joint and bone problems

If these symptoms appear, parents should talk with their child’s doctor to determine if further testing is necessary to confirm the diagnosis. Children diagnosed with Hurler syndrome typically live around 10 years, but children with milder forms can live into their 20s and 30s.

While there are several differences between Hunter syndrome and Hurler syndrome, one similarity they share is having no cure. Treatment for both of these conditions centers mainly around symptom management and quality of life. For this reason, taking part in a clinical trial can have a major impact, both on individuals today and the patients of tomorrow. To learn more about clinical trials that are currently enrolling, click the button below.