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Mucopolysaccharidosis type I

(myoo-koh-PAH-lee-SAK-uh-rie-DOH-sis • type • 1)

General Condition Information

Other Names

  • MPS I (Hurler’s syndrome)
  • MPS-I
  • MPS-I (Hurler syndrome)
  • Mucopolysaccharidosis 1
  • Mucopolysaccharidosis I
  • Mucopolysaccharidosis type 1
  • Mucopolysaccharidosis type I (Hurler syndrome)
  • Mucopolysaccharidosis type-I
  • Mucopolysaccharidosis, type I

Condition Type

Birth Prevalence

  • About 40 babies are born with the severe form of this condition each year in the United States.
  • Less than 10 babies are born with the attenuated form of this condition each year in the United States. 
  • Visit GeneReviews to learn more about how often this condition occurs.

Screening Finding

Decreased IDUA enzyme activity +/- increased GAG levels

What is Mucopolysaccharidosis type I

Mucopolysaccharidosis type I (MPS I) is one of a group of inherited (genetic) conditions that prevent the body from processing sugars properly. 

Your body uses complicated sugars called glycosaminoglycans (GAGs) in several important processes. An enzyme called alpha-L-iduronidase (IDUA) breaks down GAGs so that the body can use them. This process occurs in special compartments inside your cells called lysosomes

MPS I is a condition that occurs when IDUA is absent or present at low levels. The lysosomes then have trouble breaking down GAGs. This causes a buildup of GAGs in the tissues that can result in problems throughout the body. GAGs used to be called mucopolysaccharides, which is where the condition got its name.

There are two types of MPS I – severe and attenuated – that differ in signs, symptoms, and age of onset. The severity of the condition depends on how much IDUA activity is present. IDUA activity shows how well your baby can break down GAGs.

High levels of GAGs can damage many parts of the body. This damage leads to the signs and symptoms of the condition.

Newborn Screening and Follow-Up

Condition Details

Treatment and Management

It is important to talk to your health care provider about what type of evaluations may be useful to look for problems, and which treatment(s) are best for your baby. The goal of treatment is to prevent the health problems caused by this condition. 

Testing may include:

  • MRI or CT scans
  • X-rays
  • Ultrasound picture of the heart (echocardiogram)
  • Test of the heart’s electrical signals (electrocardiogram, ECG or EKG)
  • Hearing tests

Treatments may include the following:

Health outcomes for MPS I vary based on a child’s form of the condition. For children with the less severe form, early and ongoing treatment can lead to healthy growth and development. For children with the more severe form, early treatment can prevent or delay some serious symptoms of the condition.

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