HUNTER SYNDROME
MPS II is also known as Hunter syndrome. Children with this condition have an abnormal accumulation of complex sugars in their cells, which affects many systems in their bodies. Hunter syndrome primarily occurs in boys and is one of about 50 diseases classified as lysosomal storage disorders (LSD)
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Hunter Syndrome
Hunter syndrome is a rare, inherited genetic disorder found in children. This condition is a result of a missing or malfunctioning enzyme. In a child with Hunter syndrome, the body doesn’t have enough iduronate 2-sulfatase enzyme. This enzyme plays a crucial job in breaking down certain complex molecules. That is why without enough of this enzyme, the level of molecules develops in harmful amounts.
Gradually, the buildup of increased amounts of these harmful elements causes progressive and permanent damage. And this can affect mental development, appearance, physical abilities, organ function, etc. Hunter syndrome is far more common in boys than girls. This condition consists of a group of inherited metabolic disorders which is called mucopolysaccharidoses (MPSs). This condition is also known as MPS II. Even though there is no cure for Hunter syndrome, treatment entails managing complications and symptoms.
Symptoms
Hunter syndrome symptoms can be mild or severe. Symptoms aren’t present at birth. However, these often come to show up around ages 2 to 4 as the harmful molecules continue to build up. The symptoms may include:
- An enlarged head, thickening lips, a broad nose, flared nostrils, a protruding tongue, a deep, hoarse voice
- Abnormal-sized or shaped bone, skeletal irregularities
- A bloated abdomen, enlarged internal organs
- Chronic diarrhea, white skin growths
- Aggressive behavior, joint stiffness, stunted growth
- Delayed development (late walking or talking)
Causes
Hunter syndrome is caused by a gene mutation (abnormality) that is passed down to the child from a mother. The affected gene regulates the production of a specific enzyme that breaks down complex sugars that our body produces.
In people with the syndrome, the body does not produce enough or any of these enzymes. This causes molecules of the sugars to build up in organs and tissues and thus, damage them.
QUESTIONS AND ANSWERS
What is Hunter syndrome, and what are its symptoms?
- Hunter Syndrome: Hunter syndrome, a rare genetic disorder, developes from a deficiency of the enzyme iduronate-2-sulfatase (I2S). This deficiency leads to the buildup of certain complex carbohydrates called glycosaminoglycans (GAGs) in various tissues and organs throughout the body.
- Symptoms: Children with Hunter syndrome may experience a wide range of symptoms, including coarse facial features, enlarged liver and spleen, joint stiffness, skeletal deformities, cardiovascular issues, respiratory problems, and neurological complications. Behavioral and developmental issues can also occur.
How is Hunter syndrome diagnosed, and is there a cure?
- Diagnosis: Doctors diagnose Hunter syndrome through a combination of clinical evaluation, genetic testing, and laboratory tests to measure the levels of I2S enzyme activity and GAGs in the blood or urine. Prenatal testing can occur if there is a family history of the disorder.
- Cure: Currently, a cure for Hunter syndrome does not exist. However, doctors can treat the condition and manage the symptoms to improve the quality of life for affected children. Enzyme replacement therapy (ERT) is one such treatment that can help reduce the buildup of GAGs and alleviate some of the disease’s symptoms.
What is the prognosis for children with Hunter syndrome, and what is the recommended treatment plan?
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Prognosis: The prognosis for children with Hunter syndrome varies based on the severity of the disease and the availability of early intervention and treatment. Without treatment, the disease tends to progress, leading to severe disabilities and a shortened lifespan. With early diagnosis and ERT, the progression of the disease can be slowed, and the quality of life may be improved. However, Hunter syndrome remains a chronic and progressive condition.
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Treatment: The primary treatment for Hunter syndrome is enzyme replacement therapy (ERT) with idursulfase. This therapy can help manage some of the physical and organ-related symptoms of the disease. Supportive care, including physical therapy, occupational therapy, and speech therapy, can also be beneficial in addressing mobility and developmental issues. Regular medical check-ups and a multidisciplinary approach to care are essential to monitor and manage the child’s health effectively.
It’s important to note that Hunter syndrome is a complex condition that requires ongoing medical management, and treatment plans should be individualized based on the child’s specific needs and symptoms. Collaboration with healthcare professionals experienced in managing rare genetic disorders is crucial for providing the best care for children with Hunter syndrome.
The doctors and surgeons at the Medical City Children’s Orthopedics and Spine Specialists treat children with Hunter Syndrome. We specialize in children and adolescents.
Diagnosis
Tests used to diagnose Hunter syndrome include urine tests, blood tests, and genetic testing. The urine test helps determine if there are abnormally high levels of sugar molecules. Blood tests show if the levels of enzyme activity are low or absent. Genetic testing confirms the diagnosis by identifying gene mutations.
What Are The Risk Factors
There are two major risk factors associated with Hunter syndrome:
Sex – Hunter syndrome almost always occurs in males. Girls are at less risk of developing this disease since they inherit two X chromosomes. That is why even if one of the X chromosomes is defective, the other X chromosome can still provide a functioning gene. However, if the X chromosome of a male is defective, there isn’t any other normal X chromosome to compensate for the issue.
Family history – Generally, a defective chromosome causes Hunter syndrome. To develop the disease, a child must inherit the defective chromosome. Hunter syndrome is also known as an X-linked recessive disease. This means that women can carry this defective chromosome and can pass it on. However, mothers themselves aren’t affected by the disease. Also, it is likely they don’t know whether they have this defective chromosome or not.
When You Should See a Doctor
Even though Hunter syndrome is very uncommon, if you notice any abnormal changes in your child’s facial features, a loss of previously learned skills, bone deformities, or other symptoms listed above, consult your child’s primary care doctor. He or she can help you decide if you need to see a specialist or opt for further specialized testing.
Associated Complications
Depending on the type and severity of this condition, a variety of complications can come up with Hunter syndrome. Complications can affect the lungs, bones, brain and nervous system, heart, joints, and connective tissue.
Respiratory Issues
Breathing difficulties start showing up with an enlarged tongue, thickened gums, and thickened nasal passages and windpipe (trachea). Children with this condition also likely have chronic respiratory infections, ear, and sinus infections, pneumonia, etc. Sleep apnea is also another big problem.
Cardiac Issues
Thickening of heart tissue can lead to improper closing of heart valves. Consequently, it interrupts the heart and other parts of the body. And as the disease progresses, these cardiac problems start worsening even sometimes leading to cardiac arrest.
Connective Tissue and Skeletal Problems
The build-up of undigested complex sugar molecules in the connective tissues causes skeletal abnormalities. It affects the bones, ligaments, and joints, reducing your child’s growth, and causing physical malformations, and pain. Joint stiffness occurs because of the abnormalities of cartilage and bones and the swelling of joint connective tissues.
The group of abnormalities usually common in the bones of children with Hunter syndrome is called dysostosis multiplex. These abnormalities can cause irregularly shaped vertebrae, spines, legs, pelvises, ribs, arms, fingers, etc. In severe cases, all these bone abnormalities can cause many children with Hunter syndrome to not grow to a normal height. However, in milder cases, many children reach normal heights.
Hernias are also quite common in this condition. This is a condition when soft tissue which is usually part of the intestine, comes out through tears in the lower abdominal wall. In fact, these are often one of the first indications of the disorder. Also, an enlarged liver and spleen may put pressure on the abdomen, causing a hernia.
Brain And Nervous System Related Issues
In children with Hunter syndrome, various neurological complications are common and they continue to develop. The buildup of excess fluids in your child’s brain may cause many neurological complications such as severe headaches, poor vision, a change in the mental state, etc. Another complication is when the membranes surrounding the spinal cord become thick and scarred. This creates pressure on the upper spinal cord causing fatigue in his or her legs. As a result your child gradually weakens physically. Other disorders are carpal tunnel syndrome, poor mental development, seizures, longer recovery time, etc.
Recovery from Normal Childhood Illnesses
Children with Hunter syndrome usually take longer to recover from other normal childhood illnesses. Therefore, it’s extremely important to take general preventive measures to ensure that your child doesn’t get sick easily. For example, Make sure your child has taken a flu shot and all other necessary vaccinations.
Hunter Syndrome Prevention
So, is there a way to prevent Hunter Syndrome? Well, Hunter syndrome is genetic. So, it’s not possible to prevent it. It’s best to consult a genetic counselor if you are planning to have a child. It is important, especially when you have a family history of genetic abnormalities. The doctor may suggest a test and help you make the right decision.
Final Thoughts
While there is no cure available for Hunter syndrome, it’s possible to manage the potential complications associated with it. Experts from different fields of expertise together can help manage the problems and improve the child’s quality of life. So far, Enzyme Replacement Therapy has shown some promising results. This treatment involves replacing the missing enzyme with its man-made version.
Unfortunately, in severe cases, the life expectancy of the patient will end around 20 years. In mild cases, you can expect the patient to live longer into adulthood. Please consult one of our doctors at the Medical City Children’s Orthopedics and Spine Specialists for the right advice and guidance. We have four offices in Arlington, Dallas, Flower Mound, Frisco, and McKinney, TX. Finally, there are activities and therapies to reduce the complications. Call us for an appointment.
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Footnote:
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