Overview
Hunter syndrome is due to a deficiency of an enzyme known as iduronate 2-sulfatase. It also has a spectrum of disease where on one end you could have cognitive impairment and the other end normal cognition. This syndrome can impact cardiac function, pulmonary function, and increases the risk of recurrent ear infections. The function of this enzyme is to disintegrate several difficult molecules, your body builds up harmful molecules due to the absence of this enzyme in the body.
Hunter syndrome may affect mental health and can have a serious effect on the physical abilities of a person. This condition is affecting males when compared to females. Mucopolysaccharidoses (MPSs) is the other name of hunter syndrome. MPSs is considered as an inherited metabolic disorder. There isn’t any specific treatment for this condition and the main objective of any type of treatment is to ease the symptoms of the disease.
What are the indicators of hunter syndrome?
A baby with hunter syndrome appears healthy at birth, but then at some point in the early years of life symptoms begin to develop in multiple organ systems.
Delayed development in the walking or talking, stunted growth, stiffness in the joints, protruding tongue, white skin growths that resemble pebbles, deep voice, chronic Diarrhea, bone-in an abnormal size, aggressive behavior, distended abdomen, and an enlarged head are considered as the symptoms of Hunter syndrome.
Some infants will have only mild symptoms while others may have severe or debilitating symptoms.
When to consult a physician
It is not a common disease but take your child to a doctor or a therapist immediately if the child is experiencing any of the symptoms described above. Your doctor should evaluate your child for other possible causes of the symptoms before treating hunter syndrome. A doctor can determine the best way to manage the symptoms of the child.
What are the causes of Hunter syndrome?
The main cause of this syndrome is the formation of a defective chromosome in an infant mother. This defective chromosome can interfere with the functions of an iduronate 2-sulfatase enzyme and it results in the permanent damage of the blood and connective tissues.
What are the risk factors of hunter syndrome?
Several risk factors contributing to the cause of this condition. These risk factors include
- Family history
- Sex
Let’s discuss the above risk factors in detail
Family history
If a mother has diagnosed with this defective chromosome in the past, then a baby also has an increased risk of getting diagnosed with this syndrome. Women carry this defective disease and they continue. Some women are not aware of defective chromosomes. It is also called as an X-linked recessive disease.
Sex
When compared with girls, boys are more likely to inherit the defective chromosome and getting diagnosed with Hunter syndrome. Two X chromosomes are present in girls and even if one of the chromosomes is defective then the other one can provide normal functioning of the gene. When it comes to males, there is only one X chromosome and if it has defected then there is not another one to replace it hence it will be difficult for that chromosome to provide a functioning gene.
What are the complications of Hunter syndrome?
Several complications associated with this disease and the complications depend on the seriousness of the syndrome and it can affect the other parts of the body.
The following are the complications of hunter syndrome. It includes
- Respiratory complications
- Cardiac complications
- Skeletal and connective tissue complications
- Brain and nervous system complications
- Longer recovery from other illnesses
Let’s discuss the above complications in detail:
Respiratory complications
People with Hunter syndrome may often suffer from breathing difficulties and it is due to the nasal passages and windpipe. Other respiratory complications include
- An enlarged tongue
- Thickened gums
- Sleep apnea
Cardiac complications
Cardiac complications of hunter syndrome include an improper closing of heart valves. As a result, the blood supply to the heart and remaining parts of your body stops. It will become worse and leads to the improper function of the heart. People may experience hypertension due to cardiac complications.
Complications due to connective tissue
These complications can affect your child’s growth and can make their speech unclear, and as the condition progresses, it will be difficult for a child to walk. The connective tissues can affect your bones, joints, and ligaments negatively.
These bone abnormalities due to the cause of Mucopolysaccharidoses (MPSs) is called as dysostosis multiplex. Children with bone abnormalities may lead to irregular shaped
- Vertebrae
- Spines
- Ribs
- hands
- Fingers
- Legs
- Pelvises
Complications due to Brain and nervous system
A child with Mucopolysaccharidoses (MPSs) can develop several neurological complications. The main cause of this complication is the excess of fluid remaining in the child’s brain. It can have a serious effect on the mental health of a child and leads to other problems such as
- Severe pain in the head
- Interfere with vision
Some children may be hyperactive and while others develop fatigue and are unable to stay active physically.
Unable to recover from other health conditions
It will be difficult for children to manage other health conditions due to hunter syndrome. It takes more time to heal in children with Mucopolysaccharidoses (MPSs).
How is hunter syndrome diagnosed?
There are no tests and procedures to confirm the diagnosis of Hunter syndrome in children as they appear very healthy at the time of birth. A doctor can conduct a physical exam to look for signs like changes in facial features. As the condition progresses, the child starts to shows the indicators of this syndrome.
Prenatal testing
Prenatal testing is used to detect the defective gene in the unborn child.
What are the treatment options available for hunter syndrome?
If a doctor confirms a defective gene in the child by conducting prenatal testing, then the treatment depends on which part of the body is affected by Mucopolysaccharidoses (MPSs). The treatment of hunter syndrome includes
- Treating respiratory issues
- Addressing heart complications
- Managing neurological complications
- Managing sleep problems
- Enzyme therapy
- Stem cell transplant
- Gene therapy
Let’s discuss the above treatment options in detail:
Treating respiratory issues
People with Hunter syndrome often experience difficulties in breathing and a doctor can recommend some breathing devices to manage the problems relating to sleep.
Addressing heart complications
A child’s physician will observe the complications due to improper function of cardiac and may recommend surgery to repair the heart valves. A child’s doctor may recommend surgery if the child shows the following complications. It includes
- Hypertension
- Heart murmur
- Leaky heart valves
Treating neurological problems
A child’s physician may recommend surgery to manage the problems related to the brain and spinal cord. Anticonvulsant medications are used to treat seizures in children.
Treating behavioral complications
As Mucopolysaccharidoses (MPSs) can have a serious effect on the mental health of the child, it is advised to move your child to a safe and healthy environment. Drugs are not recommended for children to treat behavioural complications.
Managing sleep problems
Children with Mucopolysaccharidoses (MPSs) may experience sleep disturbances due to drug use. Your child’s physician may recommend the following drug to improve the children’s sleep.
- Mild sedatives
- Melatonin
Enzyme therapy
This therapy is used to remove the defective enzyme and replace it with the new one to manage the indicators of hunter syndrome. FDA approved this treatment and possible side effects of enzyme therapy includes
- Pain in the head
- A high temperature of the body
- Skin allergy
The above side effects can occur at any time after the therapy. It is advised to consult a physician when you are experiencing the side effects of this therapy. Your physician may prescribe some drugs to manage these side effects.
Stem cell transplant
The main objective of this therapy is to introduce new healthy blood stem cells into the child’s body to replace the defective enzyme. More research is needed to be done as this point lacks evidence.
Gene therapy
This therapy’s objective is to replace the chromosome and to create the missing or defective enzyme. This point lacks evidence and more research needs to be done.
Conclusion
Hunter syndrome is a serious and progressive condition for which we currently have no cure. Early detection can save lives and lessen complications after the treatment. Due to this reason, you should take your child to a child’s physician when the baby showing the symptoms. A doctor can complete a physical exam and review the medical history to determine which treatment option would be best for your child. It is important to get an accurate diagnosis and prompt treatment.
References
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614543/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7072947/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5574592/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6982257/
- https://www.researchgate.net/figure/Children-with-Hunter-syndrome-A-a-2-year-old-with-a-severe-phenotype-B-an-adult-male_fig2_264391896
Sirisha B 
Raju Ch