What is MPS1?

If your child has been diagnosed with MPS1 or is currently awaiting testing, we are here for you.

About MPS1

Mucopolysaccharidosis Type 1 (MPS1), is a rare, severe, progressive genetic disorder that falls under the category of lysosomal storage diseases. These disorders are characterized by the body’s inability to properly break down and dispose of specific complex molecules, leading to their accumulation within cells and various organs. In the case of MPS1, there is a deficiency of an enzyme called alpha-L-iduronidase. This enzyme is essential for breaking down certain complex carbohydrates called glycosaminoglycans (GAGs) in the body.

Due to the deficiency of alpha-L-iduronidase, GAGs accumulate within various tissues and organs of the body, leading to a wide range of symptoms that can affect multiple systems, including:

  • Skeletal Abnormalities: skeletal abnormalities, including short stature, joint stiffness, and deformities. This can lead to mobility issues and a characteristic appearance.
  • Carpel Tunnel occurs when the median nerve, which runs from the forearm into the hand, becomes compressed or squeezed as it passes through a narrow passageway called the carpal tunnel.
  • Trigger Finger: Just as it sounds, the sticking, locking, and snapping in fingers and/or thumb. It results from inflammation and thickening; affected tendons may not glide smoothly through the sheath. When attempting to flex your finger or thumb, it may get stuck in a bent position, and you might feel a snapping or popping sensation when you try to straighten it.
  • Cardiovascular Problems: Heart problems, such as valve abnormalities and cardiomyopathy.
  • Respiratory Issues: Enlargement of the tonsils and adenoids can lead to obstructive sleep apnea and respiratory difficulties.
  • Vision and hearing problems are common in individuals with MPS1, as the condition can affect both the eyes and ears. Hearing loss, and corneal clouding can also occur.
  • Cognitive Impairment: Depending on the subtype and severity of MPS1, individuals may experience cognitive impairment, developmental delay, and intellectual disability.
  • Organ Enlargement: Some individuals may have enlarged liver and spleen.
Even with successful treatments, patients have a lifetime of surgeries, hospital stays, and a shortened life expectancy. While we cannot reverse the damage already done, we can fight and hope to give MPS1 patients a better and higher quality chance at life.

There are three subtypes of MPS1

Hurler syndrome, Hurler-Scheie syndrome, or Scheie syndrome, depending on the severity of the condition.

The severity of the condition can vary widely, with Hurler syndrome being the most severe form and Scheie syndrome being the mildest. 

There is no cure for MPS1, but treatment options may include enzyme replacement therapy (ERT) to replace the missing enzyme, bone marrow transplantation (especially for severe cases), and various supportive therapies to manage symptoms and improve the quality of life for affected individuals.

Learn more about the symptoms, how to get diagnosed, prognosis, current research, and more below:

  • Genetic Cause: MPS1 is an autosomal recessive disorder, which means that an individual needs to inherit two copies of the defective gene (one from each parent) in order to develop the condition. The defective gene leads to a deficiency in the alpha-L-iduronidase enzyme.
  • Genetic Testing and Counseling: Genetic testing can help diagnose MPS1 before birth or in early childhood. Genetic counseling is important for families at risk of having a child with MPS1, as it can provide information about the risks and options available.
  • Accumulation of Substances: Due to the enzyme deficiency, certain large molecules called glycosaminoglycans (GAGs) build up in various tissues and organs of the body, including the bones, joints, heart, liver, spleen, and brain.
  • Symptoms: The symptoms of MPS1 can vary in severity but often include skeletal abnormalities, coarse facial features, enlarged liver and spleen, heart problems, developmental delay, and cognitive impairment. The condition can also affect the respiratory and neurological systems.
  • Treatment: Currently, there is no cure for MPS1, but there are treatments aimed at managing symptoms and improving the quality of life. Enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are among the approaches used to manage the condition. The effectiveness of treatment can vary depending on the severity of the disease. 

MPS1 is a complex disorder with a wide range of symptoms. Comprehensive care often requires a multidisciplinary medical approach.


How Common Is MPS1?

The prevalence of MPS1 can vary by subtype:

  • Hurler Syndrome: This is the most severe form of MPS1. It is estimated to occur in about 1 in 100,000 live births.
  • Hurler-Scheie Syndrome: This is an intermediate form of MPS1 with milder symptoms compared to Hurler syndrome. Its prevalence is also relatively rare, with estimates ranging from 1 in 500,000 to 1 in 1,000,000 live births.
  • Scheie Syndrome: This is the mildest form of MPS1. It is even rarer than the other two subtypes, with an estimated prevalence of 1 in 500,000 to 1 in 1,000,000 live births.

Keep in mind that these prevalence estimates can vary based on geographic location and population demographics. Advances in genetic testing and increased awareness of rare diseases may lead to more accurate diagnosis and reporting of these conditions over time.

How Is MPS1 Diagnosed?

Diagnosing MPS1, particularly Hurler syndrome, typically involves a combination of clinical evaluation, medical history, and various diagnostic tests. Here’s an overview of the diagnostic process:

  • Clinical Evaluation:
    • A healthcare provider, often a pediatrician or geneticist, will start by conducting a thorough clinical evaluation. They will gather information about the child’s medical history and family history to identify any potential risk factors or symptoms.
  • Physical Examination:
    • A physical examination may reveal certain physical characteristics commonly associated with MPS1, including coarse facial features, enlarged liver and spleen, joint stiffness, and other skeletal abnormalities.
  • Urine Test:
    • One of the initial diagnostic tests for MPS1 is a urine test. This test can detect elevated levels of glycosaminoglycans (GAGs), which are the molecules that accumulate in individuals with MPS1. A high level of GAGs in the urine can be a strong indicator of the disorder.
  • Blood Enzyme Activity Test:
    • Another important diagnostic test is a blood enzyme activity test. In MPS1, there is a deficiency of the enzyme alpha-L-iduronidase. Measuring the activity of this enzyme in a blood sample can help confirm the diagnosis. Low or absent enzyme activity is indicative of MPS1.
  • Genetic Testing:
    • Genetic testing is often performed to confirm the diagnosis and identify the specific genetic mutation responsible for MPS1. This can be done through DNA analysis, typically using a blood sample.
  • Imaging Studies:
    • Imaging studies such as X-rays, CT scans, or MRIs may be performed to assess the extent of bone and organ involvement. MPS1 can cause abnormalities in the bones and organs, and these tests can help evaluate the severity of these issues.
  • Cardiac Evaluation:
    • Individuals with MPS1, especially those with the Hurler subtype, may undergo a cardiac evaluation to assess any heart-related complications, as heart valve abnormalities can occur.
  • Ophthalmological Evaluation:
    • An eye examination may be conducted to detect any corneal clouding or other eye problems, which are common in MPS1.
  • Hearing Evaluation:
    • Hearing tests may be performed to assess any hearing loss, which can also be a symptom of MPS1.


Has Your Child Been Diagnosed with MPS I?

If your child has been diagnosed with MPS1 or is currently awaiting testing, we are here for you. This brief MPS1 guide walks you through the initial questions most families have about MPS1, including what to do next. This introductory information is intended to help you be proactive in caring for your child and giving them the best quality of life.