Hunter syndrome, a rare genetic disease that affects males, prevents sugar molecules from being properly broken down. The accumulation of these molecules causes damage to tissues and organs that affect the physical and mental development of the child. You can find more information below.
What is Hunter syndrome?
Hunter syndrome is a very rare, genetic disease caused by a missing or malfunctioning enzyme . In Hunter syndrome, the enzyme iduronate 2-sulfatase is not enough in the body. The task of this enzyme is to break down some complex molecules. Without enough of this enzyme, the molecules build up in harmful amounts.
Hunter syndrome is much more common in males. This condition is a group of inherited metabolic disorders called mucopolysaccharidosis (MPS) . This syndrome is also known as MPS 2 .
Other metabolic disorders belonging to this group include:
- Hurler-Scheie syndrome (MPS 1)
- Sanfilippo sendromu (MPS 3)
- Morquio sendromu (MPS 4)
There is no targeted therapy for Hunter syndrome. Treatment includes managing symptoms and complications.
How common is it?
Hunter syndrome is almost always diagnosed in males. Doctors diagnose it in roughly 1 in 100,000 to 170,000 men. Women can be carriers of the genetic mutation that causes MPS 2.
What causes Hunter syndrome?
This disease is caused by a gene mutation (abnormality) passed from a mother to her child. The affected gene is responsible for regulating the production of a specific enzyme (the substance that initiates chemical reactions in the body). This enzyme breaks down the complex sugars the body produces.
In people with the disease, the body does not make enough of any or more of this enzyme. The missing enzyme causes sugar molecules to accumulate in organs and tissues in the body. These buildups can damage organs and tissues throughout the body.
Who is at risk?
There are two major risk factors for developing Hunter syndrome:
- Genetic predisposition: Hunter syndrome is caused by a defective chromosome, and a child must inherit the defective chromosome to develop the disease. Hunter syndrome is known as an X-linked recessive disease, meaning that women carry the defective X chromosome that causes the disease and can pass it on. However, mothers are not affected by the disease and probably do not know that they have these defective chromosomes.
- Gender: Hunter syndrome is almost always seen in males. Girls have a lower risk of developing this disease because they inherit two X chromosomes. If one of the X chromosomes is defective, normal X chromosomes can provide a working gene. If a man’s X chromosome is defective, he doesn’t have another normal X chromosome to make up for the problem.
What are the symptoms of Hunter syndrome?
Signs and symptoms of both types of this genetic disease typically begin to appear in children between the ages of 2 and 4.
The symptoms of Hunter syndrome vary in severity and include:
- enlarged head
- thickening of the lips
- a wide nose
- a protruding language
- a deep, hoarse voice
- Abnormal bone size or shape and other skeletal irregularities
- A swollen abdomen as a result of enlarged internal organs
- chronic diarrhea
- White skin growths that resemble pebbles
- joint stiffness
- aggressive behavior
- insufficient growth
- Developmental delay, such as delayed walking or speaking
When should you see a doctor?
Hunter syndrome is very rare, but if you notice changes in your child’s facial appearance, loss of previously acquired skills, or any of the other signs or symptoms listed above, you should contact your child’s primary care doctor.
A specialist can help you decide on the necessary disclosures and whether you need further testing.
How is Hunter syndrome diagnosed?
If this genetic disease is suspected, the doctor will usually order the following tests:
- Urine test: Checks for an unusually high level of sugar molecules.
- Blood tests : May show low or absent levels of enzyme activity, which is a sign of disease.
- Genetic testing: Identifies mutations (changes) in the gene to confirm the diagnosis.
- Prenatal testing: Prenatal testing of the fluid surrounding the baby ( amniocentesis ) or a tissue sample from the placenta ( chorionic villus sampling ) can confirm whether your unborn child carries a copy of the defective gene or is affected by the disorder.
How is Hunter syndrome treated?
Prenatal testing of the fluid surrounding the baby or a sample of tissue from the placenta can confirm that your unborn child carries a copy of the defective gene or is affected by the condition, and the following treatments can be applied:
Relief for respiratory system complications
Removing the tonsils and adenoids can open up your child’s airway and help relieve sleep apnea. However, as the disease progresses, the tissues continue to thicken and these problems may return.
Respirators that use air pressure to keep the airway open can help with upper airway obstructions and sleep apnea. Keeping your child’s airway open can also help prevent low blood oxygen levels.
Addressing heart complications
Your child’s doctor will want to monitor closely for cardiovascular complications such as high blood pressure, leaky heart valves, and the like. If your child has serious cardiovascular problems, your doctor may recommend surgery to replace the heart valves.
Treatment of skeletal and connective tissue problems
Options for skeletal and connective tissue complications are limited, as most children with Hunter syndrome do not recover and often have complications after surgery. For example, when bones are fragile, surgery to stabilize the spine using internal hardware is difficult.
Your child’s joint flexibility can be improved with physical therapy, which helps relieve stiffness and maintain function. But physical therapy cannot stop the progressive decline of joint motion. Your child may eventually need to use a wheelchair due to pain and limited endurance.
Surgery can repair hernias, but results are often not ideal due to weakness in the connective tissues. The procedure needs to be repeated often. One option is to manage your child’s hernia with supportive scissors rather than surgery because of the risks of anesthesia and surgery.
Managing neurological complications
Problems with the accumulation of fluid and tissue around the brain and spinal cord are difficult to address because of the inherent risks in treating these parts of the body.
Your child’s doctor may recommend surgery to drain excess fluids or remove accumulated tissue. If your child has seizures, your doctor may prescribe certain medications.
Managing behavioral problems
If your child develops abnormal behavior as a result of Hunter syndrome, providing a safe home environment is one of the most important ways you can meet this challenge.
Treating behavior problems with medications has had limited success because most medications have side effects that can worsen other complications of the disease, such as breathing problems.
Addressing sleep issues
The sleep patterns of a child with Hunter syndrome may become more and more irregular. Sedatives, especially drugs containing melatonin, can increase sleepiness. Adhering to a strict bedtime schedule and having your child sleep in a dark room can also help. It will also work to create a safe environment in your child’s bedroom.
Some treatments have shown the potential to slow the progression of the disease and reduce its severity, but the long-term effects are unknown.
- Enzyme therapy: This treatment uses man-made or genetically engineered enzymes to replace your child’s missing or defective enzymes and relieve symptoms of illness. This treatment is administered intravenously once a week.It is given by the (IV) route. When given early enough, enzyme replacement therapy can delay or prevent some symptoms of Hunter syndrome. However, it is unclear whether the improvements seen with this treatment are significant enough to improve quality of life for people with the disease. Also, benefits in thinking and intelligence have not been seen with enzyme replacement therapy. Serious allergic reactions can occur during enzyme replacement therapy. Other possible side effects include headache, fever and skin reactions. However, side effects may decrease over time or with a dose adjustment.
- Stem cell transplant: This procedure infuses healthy blood stem cells into your child’s body in hopes that new blood cells will create the missing or defective enzyme. However, treatment results have been mixed and more research is needed.
- Gene therapy: Replacing the chromosome responsible for producing the missing enzyme could theoretically cure Hunter syndrome, but much more research is needed before such treatment can be started.
Hunter syndrome complications
Various complications may occur in Hunter syndrome, depending on the type and severity of the disease.
Complications can affect the lungs, heart, joints, connective tissue, brain, and nervous system. These are listed below under headings:
An enlarged tongue, thickened gums, and thickening of the nasal passages and windpipe (trachea) make it difficult to breathe. Children often have chronic ear and sinus infections, respiratory tract infections, and pneumonia.
Sleep apnea is a condition in which breathing is interrupted intermittently during sleep, usually due to airway narrowing.
Thickening of the heart tissue can cause the heart valves to close incorrectly. As a result, the heart and other parts of the body cannot receive blood efficiently. As the disease progresses, these conditions often get worse and typically result in heart failure.
Thickening of the tissue can also cause narrowing of the aorta and other blood vessels. This, in turn, can cause high blood pressure and narrowing of the arteries in the lungs.
Skeletal and connective tissue complications
The deposition of undigested complex sugar molecules in connective tissues results in abnormalities in bones, joints, and ligaments. This reduces your child’s growth, causes pain and physical impairment, and makes it difficult for him to move.
Joint stiffness is caused by swelling of joint connective tissues and abnormalities of cartilage and bone. If your child is in pain, they will move less, which can cause more stiffness and pain.
The group of abnormalities usually seen in the bones of people with Hunter syndrome is called dysostosis multiplex . Children with these abnormalities may develop irregularly shaped vertebrae and spines, ribs, arms, fingers, legs, and pelvises.
Bone abnormalities can cause many people with Hunter syndrome to be abnormally short. In milder cases, normal dye can be achieved.
Hernias are common in Hunter syndrome. A hernia occurs when soft tissue, which is usually part of the intestine, hits a weak spot or ruptures in the lower abdominal wall. Hernias associated with Hunter syndrome can become quite large and are often one of the first signs of the disease. Liver and spleen enlargement can increase pressure in the abdomen, causing a hernia.
Brain and nervous system complications
Children with Hunter syndrome can have and continue to develop a variety of neurological complications. Many neurological problems result from excessive fluid buildup in your child’s brain. The pressure from these fluids can cause other problems that can cause severe headaches, obstruct vision, and alter your child’s mental state.
Your child may also have thickening and scarring of the membranes surrounding the spinal cord. This causes pressure and compression of the upper spinal cord. As a result, your child may develop fatigue in his legs, gradually weaken and become less physically active.
Other disorders such as carpal tunnel syndrome can result from bone deformations and nerve compression caused by the storage of complex sugar molecules in the tissues.
Children with more severe Hunter syndrome may develop abnormal behavior. Usually, your child’s mental development is affected between the ages of 2 and 6. Some children may experience attention deficit and hyperactivity disorder. Your child may act aggressively and seem unable to perceive danger. As your child’s overall physical functioning declines, these behavior problems tend to be less serious.
Longer recovery time when sick
Recovery times from normal childhood illnesses are not comparable to Hunter syndrome. For children with Hunter syndrome, this may be much longer. As a result, be sure to take general preventive measures. For example, give your child a flu shot and make sure they have all the necessary vaccinations.
Can Hunter syndrome be prevented?
Hunter syndrome is a genetic disease. If you or any member of your family has a genetic disorder if you are considering having children, you should talk to your doctor or a genetic counselor.
If you think you may be a carrier, genetic testing may be done. If you already have a child with Hunter syndrome, you can seek advice from a doctor or genetic counselor before you have any more children.
Coping with Hunter syndrome
For parents of children with Hunter syndrome, joining a support group can be a great way to get practical information, daily living strategies, and encouragement from other parents in situations like yours. Ask your doctor if there is a group in your area.
The intense supervision that may be necessary for your child can deplete you and other caregivers physically, mentally and emotionally. If respite care is available, you can take advantage of it to take a break to meet the daily challenges of caring for your child and be more effective in the long run.