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Disease Information

Summary

Mucopolysaccharidosis type I (MPS I) is a condition that affects many parts of the body. This disorder was once divided into three separate syndromes: Hurler syndrome (MPS I-H), Hurler-Scheie syndrome (MPS I-H/S), and Scheie syndrome (MPS I-S), listed from most to least severe. Because there is so much overlap between each of these three syndromes, MPS I is currently divided into the severe and attenuated types. Children with MPS I often have no signs or symptoms of the condition at birth, although some have a soft out-pouching around the belly-button (umbilical hernia) or lower abdomen (inguinal hernia). People with severe MPS I generally begin to show other signs and symptoms of the disorder within the first year of life, while those with the attenuated form have milder features that develop later in childhood. Individuals with MPS I may have a large head (macrocephaly), a buildup of fluid in the brain (hydrocephalus), heart valve abnormalities, distinctive-looking facial features that are described as 'coarse,' an enlarged liver and spleen (hepatosplenomegaly), and a large tongue (macroglossia). Vocal cords can also enlarge, resulting in a deep, hoarse voice. The airway may become narrow in some people with MPS I, causing frequent upper respiratory infections and short pauses in breathing during sleep (sleep apnea). People with MPS I often develop clouding of the clear covering of the eye (cornea), which can cause significant vision loss. Affected individuals may also have hearing loss and recurrent ear infections. Some individuals with MPS I have short stature and joint deformities (contractures) that affect mobility. Most people with the severe form of the disorder also have dysostosis multiplex, which refers to multiple skeletal abnormalities seen on x-ray. Carpal tunnel syndrome develops in many children with this disorder and is characterized by numbness, tingling, and weakness in the hand and fingers. Narrowing of the spinal canal (spinal stenosis) in the neck can compress and damage the spinal cord. While both forms of MPS I can affect many different organs and tissues, people with severe MPS I experience a decline in intellectual function and a more rapid disease progression. Developmental delay is usually present by age 1, and severely affected individuals eventually lose basic functional skills (developmentally regress). Children with this form of the disorder usually have a shortened lifespan, sometimes living only into late childhood. Individuals with attenuated MPS I typically live into adulthood and may or may not have a shortened lifespan. Some people with the attenuated type have learning disabilities, while others have no intellectual impairments. Heart disease and airway obstruction are major causes of death in people with both types of MPS I.

About Mucopolysaccharidosis type 1

Many rare diseases have limited information. Currently, GARD aims to provide the following information for this disease:

  • Symptoms:May start to appear at any time in life.
  • Cause:This disease has more than one possible cause.
  • Organizations:Patient organizations dedicated to this rare disease are available on GARD, or you may contact a GARD Information Specialist for additional information.
  • Newborn Screening:This disease may be detected through newborn screening tests performed soon afterbirth.(Newborn screening tests may detect diseases before symptoms develop. If test results are abnormal, follow up with your medical team for additional testing and treatment options.)
  • Categories:Genetic diseases(Genetic diseases affect the DNA, or genetic instructions, which directs how tissues, organs, and body systems function.)Neurological diseases(Neurological diseases affect the brain, spinal cord, cranial nerves, autonomic nerves, or other peripheral nerves.)Inherited Metabolic diseases(Inherited metabolic diseases, or inborn errors of metabolism, are a group of genetic diseases that affect the ability of the body's cells to convert food into energy.)Birth defects(Birth defects are structural changes present at birth that can affect almost any part of the body, including how the body looks, works, or both.)Lysosomal Storage diseases(Lysosomal storage diseases are a group of genetic metabolic diseases that affect the ability of the body's cells to break down substances and remove toxins.)

Resource(s) for Medical Professionals and Scientists on This Disease:

  • ClinGen provides expert-reviewed information on genes and gene variants for use in research and medicine.
  • GeneReview provides clinical information on genetic diseases, including diagnosis, treatment, and genetic counseling.
  • MONDO provides GARD with information for this disease.
  • Orphanet provides GARD with information for this disease.

Resource(s) for Medical Professionals and Scientists on This Disease:

  • ClinGen provides expert-reviewed information on genes and gene variants for use in research and medicine.
  • GeneReview provides clinical information on genetic diseases, including diagnosis, treatment, and genetic counseling.
  • MONDO provides GARD with information for this disease.
  • Orphanet provides GARD with information for this disease.

About Mucopolysaccharidosis type 1

Many rare diseases have limited information. Currently, GARD aims to provide the following information for this disease:

  • Symptoms:May start to appear at any time in life.
  • Cause:This disease has more than one possible cause.
  • Organizations:Patient organizations dedicated to this rare disease are available on GARD, or you may contact a GARD Information Specialist for additional information.
  • Newborn Screening:This disease may be detected through newborn screening tests performed soon afterbirth.(Newborn screening tests may detect diseases before symptoms develop. If test results are abnormal, follow up with your medical team for additional testing and treatment options.)
  • Categories:Genetic diseases(Genetic diseases affect the DNA, or genetic instructions, which directs how tissues, organs, and body systems function.)Neurological diseases(Neurological diseases affect the brain, spinal cord, cranial nerves, autonomic nerves, or other peripheral nerves.)Inherited Metabolic diseases(Inherited metabolic diseases, or inborn errors of metabolism, are a group of genetic diseases that affect the ability of the body's cells to convert food into energy.)Birth defects(Birth defects are structural changes present at birth that can affect almost any part of the body, including how the body looks, works, or both.)Lysosomal Storage diseases(Lysosomal storage diseases are a group of genetic metabolic diseases that affect the ability of the body's cells to break down substances and remove toxins.)

Causes

What Causes This Disease?

Genetic Mutations

Changes in your genes (also called variants) cause Mucopolysaccharidosis type 1.

Genes are sections of DNA that contains instructions that help the body grow, develop, and function. A genetic variant is a change in your DNA's order. Parents may pass variants to their children, or they may occur randomly. They may result from viruses, environmental factors, such as UV radiation, or a combination of causes.

Most genetic variants do not cause disease. However, some can affect how a gene works and interfere with the body's normal functions. A pathogenic variant is one that causes disease.

If you think you may have this disease, collect your family health history (CDC). It may help you and your medical team to know about family members who have had the disease or similar symptoms and when those symptoms first appeared.

Read more about genetic disorders (NIH MedlinePlus). 

Genetic Mutations

Changes in your genes (also called variants) cause Mucopolysaccharidosis type 1.

Genes are sections of DNA that contains instructions that help the body grow, develop, and function. A genetic variant is a change in your DNA's order. Parents may pass variants to their children, or they may occur randomly. They may result from viruses, environmental factors, such as UV radiation, or a combination of causes.

Most genetic variants do not cause disease. However, some can affect how a gene works and interfere with the body's normal functions. A pathogenic variant is one that causes disease.

If you think you may have this disease, collect your family health history (CDC). It may help you and your medical team to know about family members who have had the disease or similar symptoms and when those symptoms first appeared.

Read more about genetic disorders (NIH MedlinePlus). 

What causes disruption in metabolism?

Mucopolysaccharidosis type 1 is caused by a disruption in a person's metabolism. Metabolism is the series of chemical reactions in our body that turns the food we eat into energy and removes toxins. Hormones and specific proteins, called enzymes, help make the right chemical reactions happen in the right order. However, genetic changes can prevent hormones or enzymes from working properly, which can lead to a disruption in metabolism such as energy not being created for the body or toxins not being removed from the body. Learn more about inherited metabolic diseases from the National Human Genome Research Institute (NHGRI).

Impaired Lysosomal Function

This disease is caused by an impairment, or issue, in lysosomal function. Lysosomes are located inside cells and contain digestive enzymes that help break down fats, sugars, and other substances to create energy for the body. Genetic mutations can affect lysosomes such as having a missing or non-functioning digestive enzyme. This can prevent cells from properly breaking down toxins or moving them out of the cell. If toxins build up, the cell may become damaged or die. Depending on their location in the body, these damaged or dead cells may affect different organs and body systems.

Can diseases be passed down from parent to child?

A biological parent can sometimes pass down genetic changes, called mutations, that cause a disease or increase the chances of developing it. This is called inheritance. Knowing if other family members have had the disease, also known as your family health history, can give your medical team important information. The Surgeon General offers a tool to help you collect your family health history.

Autosomal Recessive

Autosomal means the gene involved is located on one of the numbered chromosomes. Recessive means that a child must inherit two copies of the mutated gene, one from each biological parent, to be affected by the disease. A carrier is a person who only has one copy of the genetic mutation. A carrier usually doesn't show any symptoms of the disease.

If both biological parents are carriers, there is a 25% their child inherits both copies of the mutated gene and is affected by the disease. Additionally, there is a 50% chance their child inherits only one copy of the mutated gene and is a carrier.

Learn more about inheritance patterns from the National Library of Medicine (NLM).

Autosomal Recessive

Autosomal means the gene involved is located on one of the numbered chromosomes. Recessive means that a child must inherit two copies of the mutated gene, one from each biological parent, to be affected by the disease. A carrier is a person who only has one copy of the genetic mutation. A carrier usually doesn't show any symptoms of the disease.

If both biological parents are carriers, there is a 25% their child inherits both copies of the mutated gene and is affected by the disease. Additionally, there is a 50% chance their child inherits only one copy of the mutated gene and is a carrier.

Learn more about inheritance patterns from the National Library of Medicine (NLM).

When Do Symptoms of Mucopolysaccharidosis type 1 Begin?

Symptoms of this disease may start to appear at any time in life.

The age symptoms may begin to appear differs between diseases. Symptoms may begin in a single age range, or during several age ranges. The symptoms of some diseases may begin at any age. Knowing when symptoms may have appeared can help medical providers find the correct diagnosis.
  1. Prenatal Selected
    Before Birth
  2. Newborn Selected
    Birth-4 weeks
  3. Infant Selected
    1-23 months
  4. Child Selected
    2-11 years
  5. Adolescent Selected
    12-18 years
  6. Adult Selected
    19-65 years
  7. Older Adult Selected
    65+ years
Symptoms may start to appear at any time in life.
This information comes from Orphanet

Symptoms

You may have one or more symptoms, and they may be mild or severe. Having some or all of these symptoms does not mean you have this disease. Only a health care provider can diagnose you.

Common

Many people have these, but not everyone.

  • Abnormal form of the vertebral bodies
  • Abnormal of nasal shape (Abnormal nasal morphology)
  • Abnormal shape of end part of bone (Abnormal epiphysis morphology)
  • Abnormality of the face
  • Abnormality of the hip bone (Abnormal hip bone morphology)
  • Abnormality of the tonsils
  • Abnormality of the voice
  • Abnormality of the wide portion of a long bone (Abnormal metaphysis morphology)
  • Apnea
  • Chronic infections of the middle ear (Chronic otitis media)
  • Coarse facial features
  • Corneal opacity
  • Cough
  • Decreased size of tooth (Microdontia)
  • Depressed nasal bridge
  • Drooping lower lip (Everted lower lip vermilion)
  • Excessive hairiness over body (Generalized hirsutism)
  • Full cheeks
  • Glaucoma
  • Gum enlargement (Gingival overgrowth)
  • Hearing impairment
  • Hernia
  • Increased size of skull (Macrocephaly)
  • Increased spleen size (Splenomegaly)
  • Increased volume of lower lip (Thick lower lip vermilion)
  • Inguinal hernia
  • Intellectual disability
  • Joint pain (Arthralgia)
  • Joint stiffness
  • Long, narrow head (Dolichocephaly)
  • Loss of developmental milestones (Developmental regression)
  • Low frontal hairline (Low anterior hairline)
  • Malabsorption
  • Noninflammatory retina disease (Retinopathy)
  • Pins and needles feeling (Paresthesia)
  • Recurrent respiratory infections
  • Scoliosis
  • Sensorineural hearing impairment
  • Short stature
  • Sinus inflammation (Sinusitis)
  • Split hand
  • Thick nasal alae
  • Wide rib cage (Enlarged thorax)
  • Widely spaced teeth

Uncommon

Some people have these, but most people do not.

  • Abnormal aortic valve morphology
  • Abnormal heart valve morphology
  • Abnormal shape of tendon (Abnormal tendon morphology)
  • Cardiac failure (Congestive heart failure)
  • Death of bone due to decreased blood supply (Avascular necrosis)
  • Enlarged and thickened heart muscle (Hypertrophic cardiomyopathy)
  • Joint dislocation
  • Narrow spinal canal (Spinal canal stenosis)
  • Optic atrophy
  • Paralysis or weakness of one side of body (Hemiplegia/hemiparesis)
  • Too much cerebrospinal fluid in the brain (Hydrocephalus)
  • Visual impairment
This information comes from the Human Phenotype Ontology (HPO)

Navigating Health Care Decisions

On average, it can take more than six years to receive an accurate diagnosis. Many primary care providers (PCPs) may not be familiar with rare diseases, and patients often need to visit multiple specialists or seek second opinions to get answers.

If a diagnosis remains unclear, visiting a multidisciplinary care center or university hospital may help. These centers bring together teams of specialists who can work together to evaluate symptoms and coordinate a diagnosis. This team-based approach is also helpful after a diagnosis, when managing care for rare diseases.

Because only about 5% of rare diseases have FDA-approved treatments, finding the right healthcare team to manage your symptoms and overall health is essential. People living with rare diseases often face challenges such as delayed diagnosis, limited treatment options, and difficulty accessing knowledgeable providers. Building a care team that understands your needs can make a significant difference in your quality of life.

Your Health Care Team

Why is building the right health care team important?

Building the right health care team is key to the diagnosis, treatment, and management of your long-term health journey living with a rare disease. Start by choosing a primary care provider (PCP). Your PCP will be your main point of contact and help coordinate care with other medical professionals. Your PCP may order tests or refer you to specialists. To find a PCP near you, use the Medicare provider search tool and enter your location and “Primary Care Provider.”

Seeing multiple specialists is important for people with rare diseases because these conditions often affect many parts of the body and require care from doctors with different expertise. Most primary care providers may not be familiar with rare diseases, so involving specialists can lead to a more accurate diagnosis and better care. A coordinated team approach ensures that all symptoms are addressed and that care is well-managed. It can also connect patients with the latest research or treatment options.

A PCP that specializes in the care of children is called a pediatrician. Use this tool by the American Academy of Pediatrics to find a pediatrician in your area by inputting your location.

These specialists may help in the diagnosis, management, and treatment of Mucopolysaccharidosis type 1:

Orthopedists, also known as orthopedic surgeons, are doctors with specialized training in diagnosing and treating conditions that affect the bones, joints, muscles, tendons, and ligaments. They care for people with arthritis, scoliosis, sports injuries, bone fractures, and rare or inherited bone conditions. Orthopedists may use imaging tests and physical exams to identify the cause of pain, stiffness, or limited movement. Treatment may include physical therapy, medication, or surgery.

You may want to consider bringing a copy of your medical history and a list of any medications to your appointment.

Ask your primary care provider for a referral or use this directory by Medicare to search for an orthopedist specialist in your area. Search using the keyword “Orthopedics.”
Neurologists are doctors with specialized training in diagnosing and treating conditions that affect the brain, spinal cord, and nerves. These parts of the nervous system help control how the body moves, feels, and thinks. Neurologists often care for people with seizures, memory problems, muscle weakness, movement disorders, and inherited conditions such as muscular dystrophies. To better understand a person's symptoms, neurologists may use imaging tests that show the brain or spine, or tests that measure the brain’s electrical activity.

You may want to consider bringing a copy of your medical history and a list of any medications to your appointment.

Ask your primary care provider for a referral or use this directory provided by the American Board of Psychiatry and Neurology to find a specialist. 
Ophthalmologists are doctors with specialized training in managing serious eye problems, including those that require surgery. They may have additional experience with rare or inherited eye diseases, birth defects, or eye conditions linked to the nervous or immune system. Some ophthalmologists focus on specific areas, such as diseases of the retina or cancers of the eye. They may use imaging, vision tests, and lab work to diagnose and guide treatment.

You may want to consider bringing a copy of your medical history and a list of any medications to your appointment.

Ask your primary care provider for a referral or use this directory provided by the American Academy of Ophthalmology to find a specialist.
Geneticists are doctors trained to diagnose and manage conditions caused by genetic changes, birth defects, or metabolic disorders. Metabolic disorders affect how the body makes or uses energy. Geneticists often work alongside genetic counselors to review family history, discuss genetic risks, explain testing options, and interpret genetic test results. They help people understand how inherited conditions may affect them and their families.

You may want to consider bringing a copy of your medical history and a list of any medications to your appointment.

Ask your primary care provider for a referral or use this directory provided by the American College of Medical Genetics and Genomics to find a specialist.

Multidisciplinary Care Centers

Is It Time to Get a Second Opinion or Specialized Evaluation?

If you've visited your PCP, met with specialists, and undergone the recommended tests, but are still searching for a diagnosis, it may be time to visit an academic medical center or, for pediatric patients, a children's hospital. Academic medical centers and children's hospitals, often called multidisciplinary care centers, typically bring together specialists from different fields to work together on complex cases like rare diseases.

Multidisciplinary care centers may offer more coordinated care and be involved in clinical research, which may help reduce the time to diagnosis and provide access to emerging diagnostic tools. Specialists at these centers may have a deeper understanding of rare diseases and serve as a resource when you'd like a second opinion, particularly when test results or treatment plans are not delivering expected results.

Find hospitals that may partner with medical schools and programs in your area. 

Children’s hospitals and large teaching hospitals may also offer dedicated specialists and programs for pediatric patients with undiagnosed or rare diseases. These programs bring pediatric experts together in one place and may provide more coordinated care for your child.

Search for children's or university hospitals in your area.

Rare Disease Experts

How can you find a rare disease expert?

If a diagnosis, care management, or treatment plan remains unclear despite extensive efforts by your PCP and specialists, it may be time to find a rare disease expert for your disease, if available. A rare disease expert is a medical provider that has knowledge or training on specific rare disease(s), but there may only be a few experts in your state, region, or country. Rare disease experts may work at large research or teaching hospitals, sometimes called centers of excellence. Centers of Excellence commit to sharing knowledge and best practices that can lead to improved care and treatment for individuals living with a rare disease. 

You can also contact a GARD Information Specialist for help finding experts, centers of excellence, or clinics that focus on your disease.
You can ask your care providers for help finding an expert or use directory tools to search for experts near you. The following organization(s) may maintain a list of experts or expert centers for people living with Mucopolysaccharidosis type 1:

Find Your Community

How can patient organizations help?

Patient organizations can help patients and families connect. They build public awareness of the disease and are a driving force behind research to improve patients' lives. They may offer online and in-person resources to help people live well with their disease. Many collaborate with medical experts and researchers.

Services of patient organizations differ, but may include:

  • Ways to connect to others and share personal stories
  • Easy-to-read information
  • Up-to-date treatment and research information
  • Patient registries
  • Lists of specialists or specialty centers
  • Financial aid and travel resources


Please note: GARD provides organizations for informational purposes only and not as an endorsement of their services. Contact a GARD Information Specialist for more information on organizations that may be dedicated to this disease. Please contact an organization directly if you have questions about the information or resources it provides.


View GARD's criteria for including patient organizations, which can be found under the FAQs on our About GARD page. Request an update or to have your organization added to GARD. 

Patient Organizations

5 Organizations

National MPS Society

People With

Mucopolysaccharidosis type 1

Country

United States

World Craniofacial Foundation

People With

Craniofacial anomalies

Helpful Links
Country

United States

Children's Craniofacial Association

People With

Craniofacial anomalies

Country

United States

FACES: The National Craniofacial Association

People With

Craniofacial anomalies

Country

United States

myFace

People With

Craniofacial anomalies

Country

United States

OrganizationPeople WithHelpful LinksCountry
National MPS SocietyMucopolysaccharidosis type 1United States
World Craniofacial FoundationCraniofacial anomaliesList of ExpertsUnited States
Children's Craniofacial AssociationCraniofacial anomaliesUnited States
FACES: The National Craniofacial AssociationCraniofacial anomaliesUnited States
myFaceCraniofacial anomaliesUnited States

Participate in Research

Clinical studies are a part of clinical research and play an important role in medical advances for rare diseases. Through clinical studies, researchers may ultimately uncover better ways to treat, prevent, diagnose, and understand human diseases.

What Are Clinical Studies?

Clinical studies are medical research involving people as participants. There are two main types of clinical studies:

  1. Clinical trials determine if a new test or treatment for a disease is effective and safe by comparing groups receiving different tests/treatments.
  2. Observational studies involve recording changes over time among a specific group of people in their natural settings.

Learn more about clinical trials from this National Institutes of Health webpage.

Why Participate in Clinical Studies?

People participate in clinical trials for many reasons. People with a disease may participate to receive the newest possible treatment and additional care from clinical study staff as well as to help others living with the same or a similar disease. Healthy volunteers may participate to help others and to contribute to moving science forward.

To find the right clinical study we recommend you consult your doctors, other trusted medical professionals, and patient organizations. Additionally, you can use ClinicalTrials.gov to search for clinical studies by disease, terms, or location.

What if There Are No Available Clinical Studies?

ResearchMatch helps connect people interested in research studies  with researchers from top medical centers across the United States. Anyone from the U.S. can register with this free program funded by NIH. Researchers from participating institutions use the database to search for and invite patients or healthy volunteers who meet their study criteria to participate.

Why may you want to consider joining the All of Us Research Program?

The All of Us Research Program is inviting 1 million people from all backgrounds across the U.S. to help build one of the most diverse health databases in history. Researchers will use the data to learn how our biology, lifestyle, and environment affect health. This may one day help them find ways to treat and prevent diseases.

ClinicalTrials.gov, an affiliate of NIH, provides current information on clinical research studies in the United States and abroad. Talk to a trusted doctor before choosing to participate in any clinical study. We recommend checking this site often and searching for studies with related terms/synonyms to improve results.
Search ClinicalTrials.gov for this disease.
GARDGenetic and Rare Diseases
Information Center
Contact a GARD Information Specialist if you need help finding more information on this rare disease or available clinical studies. Please note that GARD cannot enroll individuals in clinical studies.
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Sources & References

Last Updated: September 2026