Mucopolysaccharidosis Type I


What are the first steps after an initial diagnosis of mucopolysaccharidosis type I?

The first goal after a diagnosis of mucopolysaccharidosis type I (MPS I) is to establish the extent of disease. In other words, it is important to determine where the child is at, what currently needs treatment/attention, and what may need treatment/attention in the future.

The following evaluations are recommended for persons with MPS I:

  • Skeletal survey: this determines how curved the spine is and what issues there are with the joints.
  • Ophthalmologic examination: a detailed eye exam.
  • Cardiac evaluation: examination of the heart using echocardiogram (an ultrasound for the heart).
  • Hearing assessment: to check for hearing loss/deficit.
  • ENT assessment: exam by an ear-nose-throat doctor.
  • Consultation with a genetic counselor: a genetics professional who can help educate about MPS I, what it means for the child and the family, and provide support.
  • Developmental assessment: check if the child is meeting milestones and on track for age.
  • Spinal cord and nerve assessment
  • Cranial imaging: imaging of the head, preferably by MRI
  • Consideration of a sleep study

The National MPS Society has compiled a list of MPS genetics centers; this can be found by visiting their website at The Oregon Health and Science University has created a map of all the metabolic clinics in the United States to help families find the one closest to them. To search this map, please visit the OHSU website.

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Is there a treatment for Mucopolysaccharidosis type I?

Is there a treatment for Mucopolysaccharidosis type I?

Treatment, but no cure, is available for people with mucopolysaccharidosis I (MPS I). There is an FDA-approved enzyme replacement therapy (ERT) called Aldurazyme (laronidase). Aldurazyme is also approved in many countries around the globe so ask your healthcare professional if treatment is available in your specific country.

Aldurazyme is given every week by an intravenous (IV, or needle placed into a vein) infusion over about 4 hours for the rest of a person's life. It can improve lung function, increase the range of motion in joints, increase endurance, and reduce the enlarged organs to a normal size. Aldurazyme is not able to reach the brain when given by IV infusion. Therefore, it does not treat the cognitive and developmental regression seen in children with the severe form of MPS I. It is recommended that children with the severe form of MPS I receive a hematopoietic stem cell transplant (HSCT, also called a bone marrow transplant) before 2 years of age. In this procedure, children are given cells that make the alpha-L-iduronidase enzyme from a donor who does not have MPS I. The cells engraft, or seed, into the bone marrow and begin producing the alpha-L-iduronidase enzyme. The cells continue producing the enzyme for the rest of a person's life. The cells are distributed all over the body, including the brain. HSCT is able to prevent or stabilize cognitive and developmental regression (intellectual disability and loss of skills) in children with severe MPS I. It is not able to improve regression (give back skills that have been lost). This is why it should be done before 2 years of age, so children may receive it before they start regressing. HSCT also helps the other symptoms of MPS I, except for many of the bone problems and the corneal clouding. There are many risks associated with HSCT, and some are life threatening. HSCT is considered "worth the risk" in children with the severe form of MPS I, but not in people with attenuated MPS I. The corneal clouding in people with MPS I can be treated with corneal transplants. The cloudy corneas are removed from the eye and replaced with clear corneas from a donor who did not have MPS I. The clear corneas graft, or heal, onto the eyes of the person with MPS I. The corneas remain clear for the rest of the person's life.

For more information on treatment, please visit

  • Mucopolysaccharidosis Type I. NORD Rare disease information.
  • Clarke LA. Mucopolysaccharidosis Type I. Gene Reviews.

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