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Hunter Syndrome

What is Hunter Syndrome?

 

Hunter Syndrome, also known as Mucopolysaccharidosis type II (MPS II), is a type of inherited metabolic and lysosomal storage disorders. Hunter Syndrome is an ultra-rare genetic disorder caused by the missing or loss of function of an important enzyme, iduronate 2-sulfatase (I2S). This enzyme is normally found in the lysosomes of the cells, a cellular compartment responsible for breaking down and recycling molecules such as fats and sugars. I2S enzyme functions to break down a type of complex sugar molecule called glycosaminoglycans (GAGs). In patients afflicted with the Hunter Syndrome, the I2S enzyme is either absent or functionally inactive, which in turn fails to digest GAGs and leads to GAGs accumulation in the body's cells. The buildup of massive amounts of GAGs harms the cells and eventually causes permanent, and progressive damage to the affected individuals affecting their appearance, cognitive function, organ function, and physical abilities. There is currently no cure for Hunter syndrome. 

 

Synonyms

  • Mucopolysaccharidosis type II

 

Hunter Syndrome, also known as Mucopolysaccharidosis type II (MPS II), is a type of inherited metabolic and lysosomal storage disorders. Hunter Syndrome is an ultra-rare genetic disorder caused by the missing or loss of function of an important enzyme, iduronate 2-sulfatase (I2S). This enzyme is normally found in the lysosomes of the cells, a cellular compartment responsible for breaking down and recycling molecules such as fats and sugars. I2S enzyme functions to break down a type of complex sugar molecule called glycosaminoglycans (GAGs). In patients afflicted with the Hunter Syndrome, the I2S enzyme is either absent or functionally inactive, which in turn fails to digest GAGs and leads to GAGs accumulation in the body's cells. The buildup of massive amounts of GAGs harms the cells and eventually causes permanent, and progressive damage to the affected individuals affecting their appearance, cognitive function, organ function, and physical abilities. There is currently no cure for Hunter syndrome. 

Acknowledgement of Hunter Syndrome has not been added yet.

 

Hunter syndrome is a rare genetic disorder affecting 1 in 100,000 to 1 in 170,000 primarily males.

Name Abbreviation
Mucopolysaccharidosis type II MPS II

 

Hunter syndrome is caused by mutations in the gene, iduronate 2-sulfatase (IDS). Over 300 mutations have been identified, and the majority of the mutations are missense mutations, with one building block (nucleotide) change in the DNA molecule. IDS is located on the sex-determining chromosome, the X chromosome. The IDS mutations are inherited in an X-chromosome recessive pattern. Normally, people need to inherit mutations in both chromosomes to get the disorder. However, because male babies have only one X chromosome, a single altered copy of the IDS gene is enough to cause disease in boys. Thus Hunter syndrome primarily affects boys. Women who carry one normal X chromosome and one X chromosome with the disease mutations are “carriers”. 

 

IDS provides instructions for synthesizing the enzyme iduronate 2-sulfatase (I2S). I2S is located in the cellular lysosome and is responsible for breaking down large sugar molecules known as glycosaminoglycans (GAGs). In particular, I2S removes a chemical group called sulfate from two GAGs, heparan sulfate, and dermatan sulfate. The pathogenic mutations in the IDS gene partially or completely reduce the enzyme activity of I2S, which leads to GAGs accumulation in the lysosome of the cells, disrupting normal cellular function and ultimately causing multiple organ injury in the affected individuals. 

Newborns with Hunter syndrome typically do not have signs or symptoms at birth. As children grow, they begin to develop symptoms around ages 2 to 4 that can fall on a wide spectrum. The symptoms and signs may include enlarged head, thickening of the lips, broad nose and flared nostrils, protruding tongue, deep voice, skeletal irregularities, enlarged internal organs, chronic diarrhea, joint stiffness, aggressive behaviors, and global developmental delay. 

 

In addition to the manifested symptoms, a variety of complications can occur depending on the severity of the disease. These complications can affect organ systems throughout the body, including the lungs, heart, joints, connective tissue, and the nervous system. 

  1. Respiratory system:  because of the enlarged tongue and the thickening of the windpipe, breathing can be difficult. This can lead to sleep apnea in children, in which the breathing is intermittently interrupted during sleep as the airway is constricted. Children also experience chronic respiratory and ear infections. 

  2. Heart: as the children develop, the cardiac tissue may thicken and the heart cannot pump blood to the rest of the body efficiently, which may ultimately lead to cardiac failure. 

  3. Skeleton and bones: the abnormal accumulation of undigested complex sugar molecules in the bones and joints can result in slow growth, pain, joint stiffness, and physical abnormalities in children. Children may also develop irregularly shaped vertebrae, spine, rib, arm finger, leg, and pelvic bones. 

  4. Brain: the neurological complications in the Hunter syndrome can be presented as seizure, hyperactivity, aggression, and trouble paying attention or following directions. The mental development will become affected between ages 2 and 6. 

Babies born with Hunter syndrome always appear healthy at birth. As they grow, they first can display changes in facial features as a sign that something is wrong. The disease progresses slowly and the signs can overlap with many other disorders. The journey to a definitive diagnosis can take a long time.

 

Genetic testing with pathogenic mutations in the IDS gene can confirm the diagnosis. In addition, deficiency enzymes and excess amounts of complex sugar molecules can be checked in the urine samples as validations. 

 

Prenatal genetic testing with amniocentesis, which samples fluids that surrounds the baby, or chorionic villus sampling, which tests the genetic information from the placenta can be used to detect the defective gene in the unborn child. 

 

Currently, the treatment for Hunter syndrome lies in the management and relief from disease complications. For example, to control for the respiratory complications, the tonsils from the affected children can be removed, or breathing devices can be used to open up the airways to ease the sleep apnea. The heart needs to be watched closely for a heart murmur (blood backflow), high blood pressure, etc. For skeletal problems, physical therapy can help increase the flexibility of the joints, but cannot outcompete the progressive decline of the joint motion. 

 

There are some emerging treatments that have shown the potential of slowing disease progression. The FDA-approved enzyme replacement therapy (ERT) uses artificially engineered I2S enzymes to replace patients’ missing or defective enzymes through intravenous injection once a week to ease the disease symptoms. When given early, ERT may delay or alleviate some of the symptoms of Hunter syndrome. However, it is unclear whether the improvement associated with ERT treatment can significantly improve patients’ quality of life. ERT cannot cross the blood-brain barrier, a semipermeable border between the blood and the brain that controls material exchange between the blood network and the central nervous system. Therefore, the benefits in cognition and behaviors have not been seen with ERT. 

Depending on the types of genetic mutations, Hunter syndrome can vary from person to person. The most deleterious IDS mutations that lead to complete loss of enzyme function can lead to severe disease symptoms. The most severe cases can be life-threatening, with life expectancy typically between 10 and 20 years. People with mild cases typically live into adulthood. Treatment towards relieving disease complications can help manage the challenges the disease presents and improve patients’ quality of life. 

 

Tips or Suggestions of Hunter Syndrome has not been added yet.

  1. MSP II (Hunter syndrome), Available from: https://mpssociety.org/learn/diseases/mps-ii/

 

  1. Hunter syndrome, Available from: https://www.mayoclinic.org/diseases-conditions/hunter-syndrome/diagnosis-treatment/drc-20350712

 

  1. Wraith, J. E., Scarpa, M., Beck, M., Bodamer, O. A., De Meirleir, L., Guffon, N., Meldgaard Lund, A., Malm, G., Van der Ploeg, A. T., & Zeman, J. (2007). Mucopolysaccharidosis type II (Hunter syndrome): a clinical review and recommendations for treatment in the era of enzyme replacement therapy. European Journal of Pediatrics, 167(3), 267–277. https://doi.org/10.1007/s00431-007-0635-4

 

  1. Muenzer, J., Bodamer, O., Burton, B., Clarke, L., Frenking, G. S., Giugliani, R., Jones, S., Rojas, M. V. M., Scarpa, M., Beck, M., & Harmatz, P. (2011). The role of enzyme replacement therapy in severe Hunter syndrome—an expert panel consensus. European Journal of Pediatrics, 171(1), 181–188. https://doi.org/10.1007/s00431-011-1606-3

 

  1. Mucopolysaccharidoses fact sheet. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Mucopolysaccharidoses-Fact-Sheet. Accessed Nov. 1, 2018.

 

Community Details Update Created by RareshareTeam
Last updated 12 May 2021, 12:47 AM

Posted by RareshareTeam
12 May 2021, 12:47 AM

Hi everyone,

The Hunter Syndrome community details have been updated. We added more information about the cause, prevalence, symptoms, diagnosis, and treatment. Hopefully, you find it helpful. 

Best regards, 

RareShare Team 

New book by mother of Hunter Syndrome patient: Ethan and Me, by Geraldine Renton, Tribes Press. Created by RareshareTeam
Last updated 16 Mar 2021, 02:04 AM

Posted by RareshareTeam
16 Mar 2021, 02:04 AM

Ethan & Me is one family’s story of courage through adversity as they raise a child with special needs.
It’s a story that supports other families with a newly diagnosed special needs child or those who are already on that journey by imparting words of wisdom and understanding. There are many laugh out loud moments in the midst of the daily challenges, and more than all of this, there is a message of hope.

Learning more Created by rcrozier
Last updated 10 Jul 2009, 07:23 PM

Community News Articles
Huntersyndrome  1

May 15th is MPS Awareness Day!

Publication date: 13 May 2021

Community: Hunter Syndrome

Mucopolysaccharidosis (MPS) is a collection of rare genetic diseases characterized by a deficiency in an enzyme involved in the breakdown of certain long chain sugar molecules.  The accumulation of these molecules over time produces symptoms typically appearing in early childhood and progressing to organ failure and reduced life expectancy.  There are 7 known types of MPS.  MPS II or Hunter Syndrome affects about 1:162,000 babies.  May 15th is MPS Awareness Day.  Learn more about MPS by following the links below.


Rentons

Ethan and Me Podcast

Publication date: 25 May 2021

Community: Hunter Syndrome

Podcast

Listen to RareShare's latest podcast with Geraldine Renton, book author and Irish mother of a Hunter Syndrome child. In this episode, Geraldine tells of her family's journey navigating the challenges of a rare disease that led to the writing of her book Ethan and Me


Community External News Link
Title Date Link
Hunter Syndrome: Bozeman boy’s family looks into gene therapy to cure rare disease - NBC Montana 07/17/2018
Hunter Syndrome: Talking about rare disease 08/13/2018
Sangamo Announces 16 Week Clinical Results Including Reductions In Glycosaminoglycans In Phase 1/2 Trial Evaluating SB-913, A Zinc Finger Nuclease Genome Editing Treatment For MPS II (Hunter Syndrome) 12/25/2018
Denali's Hunter Syndrome Candidate Gets Orphan Drug Status 06/16/2019
Community Resources
Title Description Date Link

Clinical Trials


Cords registry

CoRDS, or the Coordination of Rare Diseases at Sanford, is based at Sanford Research in Sioux Falls, South Dakota. It provides researchers with a centralized, international patient registry for all rare diseases. This program allows patients and researchers to connect as easily as possible to help advance treatments and cures for rare diseases. The CoRDS team works with patient advocacy groups, individuals and researchers to help in the advancement of research in over 7,000 rare diseases. The registry is free for patients to enroll and researchers to access.

Enrolling is easy.

  1. Complete the screening form.
  2. Review the informed consent.
  3. Answer the permission and data sharing questions.

After these steps, the enrollment process is complete. All other questions are voluntary. However, these questions are important to patients and their families to create awareness as well as to researchers to study rare diseases. This is why we ask our participants to update their information annually or anytime changes to their information occur.

Researchers can contact CoRDS to determine if the registry contains participants with the rare disease they are researching. If the researcher determines there is a sufficient number of participants or data on the rare disease of interest within the registry, the researcher can apply for access. Upon approval from the CoRDS Scientific Advisory Board, CoRDS staff will reach out to participants on behalf of the researcher. It is then up to the participant to determine if they would like to join the study.

Visit sanfordresearch.org/CoRDS to enroll.

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Ger

I'm Ger from Galway Ireland.

I am mammy to Ethan,my angel who passed away suddenly in September 2020.

 

Ethan had Hunter Syndrome.

 

I've been writing about Ethan and our journey...

I'm the aunt of an adorable little boy with Hunter.
Hello, My grandson, Luke was diagnosed with Hunter syndrome on dec 2015. I am trying to find help and resources for my Son and Daughter n law. Any info on this is appreciated. Luke will be starting...
i am a father of a girl who affected by SANFILIPPO SYNDROME

 

called MPS IIIB aged just 8 years

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Community Details Update

Created by RareshareTeam | Last updated 12 May 2021, 12:47 AM

Learning more

Created by rcrozier | Last updated 10 Jul 2009, 07:23 PM


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