Mucopolysaccharidosis type II
MPS II; Hunter syndrome; Lysosomal storage disease - mucopolysaccharidosis type II; Iduronate 2-sulfatase deficiency; I2S deficiencyMucopolysaccharidosis type II (MPS II) is a rare disease in which the body is missing or does not have enough of an enzyme needed to break down long chains of sugar molecules. These chains of molecules are called glycosaminoglycans (formerly called mucopolysaccharides). As a result, the molecules build up in different parts of the body and cause various health problems.
Enzyme
Enzymes are complex proteins that cause a specific chemical change. For example, they can help break down the foods we eat so the body can use them....
Read Article Now Book Mark ArticleThe condition belongs to a group of diseases called mucopolysaccharidoses (MPSs). MPS II is also known as Hunter syndrome.
There are several other types of MPSs, including:
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MPS I (Hurler syndrome; Hurler-Scheie syndrome; Scheie syndrome)
MPS I
Mucopolysaccharidosis type I (MPS I) is a rare disease in which the body is missing or does not have enough of an enzyme needed to break down long ch...
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MPS III (Sanfilippo syndrome)
MPS III
Mucopolysaccharidosis type III (MPS III) is a rare disease in which the body is missing or does not have enough of certain enzymes needed to break do...
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MPS IV (Morquio syndrome)
MPS IV
Mucopolysaccharidosis type IV (MPS IV) is a rare disease in which the body is missing or does not have enough of an enzyme needed to break down long ...
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Causes
MPS II is a genetic disorder. This means it can be passed down through families. The affected gene is on the X chromosome. Boys are most often affected because they inherit the X chromosome from their mothers. Their mothers do not have symptoms of the disease, but they carry a nonworking copy of the gene.
MPS II is caused by a lack of the enzyme iduronate sulfatase. Without this enzyme, chains of sugar molecules build up in various body tissues, causing damage.
The early-onset, severe form of the disease begins shortly after age 2. A late-onset, mild form causes less severe symptoms to appear later in life.
Symptoms
In the early-onset, severe form, symptoms include:
- Aggressive behavior
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Hyperactivity
Hyperactivity
Hyperactivity means having increased movement, impulsive actions, a shorter attention span, and being easily distracted.
Read Article Now Book Mark Article - Mental function gets worse over time
- Severe intellectual disability
Intellectual disability
Intellectual disability is a condition diagnosed before age 18 that includes below-average intellectual function and a lack of skills necessary for d...
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In the late (mild) form, there can be mild to no mental deficiency.
In both forms, symptoms include:
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Carpal tunnel syndrome
Carpal tunnel syndrome
Carpal tunnel syndrome is a condition in which there is excessive pressure on the median nerve at the wrist. This is the nerve that allows feeling a...
Read Article Now Book Mark Article - Coarse features of the face
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Deafness (gets worse over time)
Deafness
Hearing loss is being partly or totally unable to hear sound in one or both ears.
Read Article Now Book Mark Article - Increased hair growth
- Joint stiffness
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Large head
Large head
Increased head circumference is when the measured distance around the widest part of the skull is larger than expected for the child's age and backgr...
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Exams and Tests
A physical exam and tests may show:
- Abnormal retina (back of the eye)
Retina
The retina is the light-sensitive layer of tissue at the back of the eyeball. Images that come through the eye's lens are focused on the retina. Th...
Read Article Now Book Mark Article - Decreased iduronate sulfatase enzyme in blood serum or cells
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Heart murmur and leaky heart valves
Heart murmur
A heart murmur is a blowing, whooshing, or rasping sound heard during a heartbeat. The sound is caused by turbulent (rough) blood flow through the h...
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Enlarged liver
Enlarged liver
Enlarged liver refers to swelling of the liver beyond its normal size. Hepatomegaly is another word to describe this problem. If both the liver and ...
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Enlarged spleen
Enlarged spleen
Splenomegaly is a larger-than-normal spleen. The spleen is an organ in the upper left part of the belly.
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Hernia in the groin
Hernia in the groin
A hernia is a sac formed by the lining of the abdominal cavity (peritoneum). The sac comes through a hole or weak area in the strong layer of the be...
Read Article Now Book Mark Article - Joint contractures (from joint stiffness)
Contractures
A contracture develops when the normally stretchy (elastic) tissues are replaced by nonstretchy (inelastic) fiber-like tissue. This tissue makes it ...
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Tests may include:
- Enzyme study
- Genetic testing for a change in the iduronate sulfatase gene
- Urine test for heparan sulfate and dermatan sulfate
Treatment
The medicine called idursulfase (Elaprase), which replaces the enzyme iduronate sulfatase may be recommended. It is given through a vein (IV, intravenously). Talk to your health care provider for more information.
Bone marrow transplant has been tried for the early-onset form, but the results can vary.
Bone marrow transplant
A bone marrow transplant is a procedure to replace damaged or diseased bone marrow with healthy bone marrow stem cells. Bone marrow is the soft, fatt...
Read Article Now Book Mark ArticleEach health problem caused by this disease should be treated separately.
Support Groups
More information and support for people with MPS II and their families can be found at:
- National MPS Society -- mpssociety.org/
- National Organization for Rare Disorders -- rarediseases.org/rare-diseases/mucopolysaccharidosis-type-ii-2/
- NIH Genetic and Rare Diseases Information Center -- rarediseases.info.nih.gov/diseases/6675/mucopolysaccharidosis-type-ii
Outlook (Prognosis)
People with the early-onset (severe) form usually live for 10 to 20 years. People with the late-onset (mild) form usually live 20 to 60 years.
Possible Complications
These complications may occur:
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Airway obstruction
Airway obstruction
Blockage of the upper airway occurs when the upper breathing passages become narrowed or blocked, making it hard to breathe. Areas in the upper airw...
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- Hearing loss that gets worse over time
- Loss of ability to complete daily living activities
- Joint stiffness that leads to contractures
- Mental function that gets worse over time
When to Contact a Medical Professional
Contact your provider if:
- You or your child has a group of these symptoms
- You know you are a genetic carrier and are considering having children
Prevention
Genetic counseling is recommended for couples who want to have children and who have a family history of MPS II. Prenatal testing is available. Carrier testing for female relatives of affected males is also available.
Genetic counseling
Shiga-like toxin producing E coli hemolytic-uremic syndrome (STEC-HUS) is a disorder that most often occurs when an infection in the digestive system...
Read Article Now Book Mark ArticleReferences
Pyeritz RE. Inherited diseases of connective tissue. In: Goldman L, Schafer AI, eds. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 239.
Spranger JW. Mucopolysaccharidoses. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 107.
Turnpenny PD, Ellard S, Cleaver R. Inborn errors of metabolism. In: Turnpenny PD, Ellard S, Cleaver R, eds. Emery's Elements of Medical Genetics and Genomics.16th ed. Philadelphia, PA: Elsevier; 2022:chap 18.
Review Date: 4/24/2023
Reviewed By: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.