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Disease Profile

Mucopolysaccharidosis type I

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

1-9 / 1 000 000

US Estimated

Europe Estimated

Age of onset

All ages





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

MPS 1; Attenuated MPS I (subtype, includes Hurler-Scheie and Scheie syndrome); Severe MPS I (subtype, also known as Hurler syndrome);


Newborn Screening


Mucopolysaccharidosis type I (MPS I) is a condition that affects many parts of the body. It is a progressively debilitating disorder; however, the rate of progression varies among affected individuals. MPS I is caused by mutations in the IDUA gene. These mutations lead to reduced levels or the complete lack of the IDUA enzyme. Without the proper amount of this enzyme, large sugar molecules called glycosaminoglycans (GAGs) accumulate within cells called lysosomes. This causes the lysosomes to increase in size, causing many different organs and tissues of the body to become enlarged. This leads to the medical problems seen in the condition.[1][2] 

MPS I was once divided into three separate syndromes: Hurler syndrome, Hurler-Scheie syndrome, and Scheie syndrome, listed from most to least severe. Because no biochemical differences have been identified and the clinical findings overlap, the condition is now divided into two subtypes, severe MPS I and attenuated MPS I.[1][2] People with severe MPS I typically have an earlier onset of symptoms, a decline in intellectual function, and a shorter lifespan. Although there is no cure for MPS I, bone marrow transplant and enzyme replacement therapy are treatment options that may help manage the symptoms of this condition.[1]


The signs and symptoms of mucopolysaccharidosis type I (MPS I) are not present at birth, but they begin to appear during childhood. People with severe MPS I develop the features of this condition earlier than those with attenuated MPS I. The following list includes the most common signs and symptoms of MPS I:[1]

  • Enlarged head, lips, cheeks, tongue, and nose
  • Enlarged vocal cords, resulting in a deep voice
  • Frequent upper respiratory infections
  • Sleep apnea
  • Hydrocephalus
  • Hepatosplenomegaly (enlarged liver and spleen)
  • Umbilical hernia
  • Inguinal hernia
  • Hearing loss
  • Recurrent ear infections
  • Corneal clouding
  • Carpal tunnel syndrome
  • Narrowing of the spinal canal (spinal stenosis)
  • Heart valve abnormalities, which can lead to heart failure
  • Short stature
  • Joint deformities (contractures)
  • Dysostosis multiplex (generalized thickening of most long bones, particularly the ribs)
  • Developmental delays and regression 

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Abnormal form of the vertebral bodies
Abnormality of epiphysis morphology
Abnormal shape of end part of bone
Abnormality of the metaphysis
Abnormality of the wide portion of a long bone
Abnormality of the voice
Voice abnormality
Chronic otitis media
Chronic infections of the middle ear
Coarse facial features
Coarse facial appearance
Corneal opacity
Generalized hirsutism
Excessive hairiness over body
Inguinal hernia
Joint stiffness
Stiff joint
Stiff joints

[ more ]

Short stature
Decreased body height
Small stature

[ more ]

Sinus inflammation
Increased spleen size
Split hand
Claw hand
Claw hand deformities
Claw hands
Claw-hand deformities

[ more ]

30%-79% of people have these symptoms
Abnormal nasal morphology
Abnormal of nasal shape
Abnormal of shape of nose

[ more ]

Abnormality of the hip bone
Abnormality of the hips
Abnormality of the tonsils
Joint pain
Depressed nasal bridge
Depressed bridge of nose
Flat bridge of nose
Flat nasal bridge
Flat, nasal bridge
Flattened nasal bridge
Low nasal bridge
Low nasal root

[ more ]

Developmental regression
Loss of developmental milestones
Mental deterioration in childhood

[ more ]

Long, narrow head
Tall and narrow skull

[ more ]

Enlarged thorax
Wide rib cage
Everted lower lip vermilion
Drooping lower lip
Outward turned lower lip

[ more ]

Full cheeks
Apple cheeks
Big cheeks
Increased size of cheeks
Large cheeks

[ more ]

Gingival overgrowth
Gum enlargement
Intellectual disability
Mental deficiency
Mental retardation
Mental retardation, nonspecific

[ more ]

Low anterior hairline
Low frontal hairline
Low-set frontal hairline

[ more ]

Increased size of skull
Large head
Large head circumference

[ more ]

Intestinal malabsorption
Decreased width of tooth
Pins and needles feeling

[ more ]

Recurrent respiratory infections
Frequent respiratory infections
Multiple respiratory infections
respiratory infections, recurrent
Susceptibility to respiratory infections

[ more ]

Noninflammatory retina disease
Sensorineural hearing impairment
Thick lower lip vermilion
Increased volume of lower lip
Plump lower lip
Prominent lower lip

[ more ]

Thick nasal alae
Widely spaced teeth
Wide-spaced teeth
Widely-spaced teeth

[ more ]

5%-29% of people have these symptoms
Abnormal aortic valve morphology
Abnormal tendon morphology
Abnormal shape of tendon
Avascular necrosis
Death of bone due to decreased blood supply
Congestive heart failure
Cardiac failure
Cardiac failures
Heart failure

[ more ]

Paralysis or weakness of one side of body
Too much cerebrospinal fluid in the brain
Hypertrophic cardiomyopathy
Enlarged and thickened heart muscle
Joint dislocation
Joint dislocations
Recurrent joint dislocations

[ more ]

Optic atrophy
Spinal canal stenosis
Narrow spinal canal
Visual impairment
Impaired vision
Loss of eyesight
Poor vision

[ more ]

Percent of people who have these symptoms is not available through HPO
Aortic regurgitation


Mutations in the IDUA gene cause mucopolysaccharidosis type I (MPS I). The IDUA gene provides instructions for producing an enzyme (alpha-L-iduronidase) that is involved in the breakdown of large sugar molecules called glycosaminoglycans (GAGs). Mutations in the IDUA gene reduce or completely eliminate the function of alpha-L-iduronidase. This leads to the accumulation of GAGs within cells, specifically inside the lysosomes. Lysosomes are compartments in the cell that digest and recycle different types of molecules. Conditions that cause molecules to build up inside the lysosomes, including MPS I, are called lysosomal storage disorders. The accumulation of GAGs increases the size of the lysosomes, which is why many tissues and organs are enlarged in this disorder.[1][3]


Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Newborn Screening

  • Baby's First Test is the nation's newborn screening education center for families and providers. This site provides information and resources about screening at the local, state, and national levels and serves as the Clearinghouse for newborn screening information.


    Management of mucopolysaccharidosis type I (MPS I) requires a multidisciplinary team given the wide range of symptoms. This team may include: primary care; cardiology; pulmonology; gastroenterology; neurology; ear, nose, and throat specialists; audiology; ophthalmology; orthopedics; physical therapy; dental; and developmental specialists.[4]

    The two main treatment options for MPS I include hematopoietic stem cell transplant (HSCT) and enzyme replacement therapy (ERT). Both of these treatments work by replacing the missing IDUA enzyme (alpha-L-iduronidase).[1]

    HSCT is considered standard of care for individuals with severe MPS I; however, its success is dependent on timing of treatment. It is typically recommended that HSCT occur early in the disease process, prior to two years of age. Studies have shown that when successful, HSCT can improve facial, auditory, and cardiac manifestations. The effect on intellectual development is unclear with some studies suggesting an improvement, while others report a slowing of cognitive decline.[1][4]

    A drug called laronidase or Aldurazyme is the enzyme replacement therapy for MPS I. Treatment with laronidase can improve problems with breathing, growth, the bones, joints and heart. However, this treatment is not expected to treat problems with mental development because laronidase cannot cross the blood-brain barrier.[1][4]

    FDA-Approved Treatments

    The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition. Learn more orphan products.

    • laronidase(Brand name: Aldurazyme) Manufactured by BioMarin Pharmaceutical, Inc.
      FDA-approved indication: Treatment for patients with Hurler and Hurler-Scheie forms of Mucopolysaccharidosis I (MPS I) and for patients with the Scheie form who have moderate to severe symptoms
      National Library of Medicine Drug Information Portal


    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

        In-Depth Information

        • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Mucopolysaccharidosis type I. Click on the link to view a sample search on this topic.

          Selected Full-Text Journal Articles


            1. Clarke LA, Heppner J. Mucopolysaccharidosis Type I. GeneReviews. February 11, 2016; https://www.ncbi.nlm.nih.gov/books/NBK1162/.
            2. Mucopolysaccharidosis type I. Genetics Home Reference (GHR). December 2012; https://ghr.nlm.nih.gov/condition/mucopolysaccharidosis-type-i.
            3. IDUA. Genetics Home Reference. May 17, 2016; https://ghr.nlm.nih.gov/gene/IDUA.
            4. Joseph Muenzer, James E. Wraith, Lorne A. Clarke. Mucopolysaccharidosis I: Management and Treatment Guidelines. Pediatrics. January 2009; 123(1):https://www.ncbi.nlm.nih.gov/pubmed/19117856. Accessed 5/23/2016.

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