Hunter's syndrome

Mucopolysaccharidosis 2.

INCIDENCE

• The condition known as Hunter's syndrome is an example of a defect in the metabolism of the mucopolysaccharides, which are complex sugars. In each of these syndromes, which include Hurler's syndrome, Morquio's syndrome, and San Filippo syndrome, there is a deficiency of a particular enzyme that is responsible for controlling the metabolism of these nutrients. (Other syndromes in this group include San Filippo syndrome.)
• Hunter's syndrome affects approximately one person in every one hundred thousand live births. Only males have been found to be affected by Hunter syndrome because of the way that it is passed down through generations. It would appear that people of every race on the planet are at risk of being affected by this.

HISTORY

• Only seven mucopolysaccharide syndromes had been identified up until a relatively recent point in time; each one was brought on by a unique enzyme deficiency.
• Recent research has led to the discovery of 11 variants, each of which has a flawed ability to metabolize a complex sugar. It is possible that additional enzyme defects similar to those described above will occur.

CAUSATION

• As a result of the fact that Hunter syndrome is passed down in a manner that is X-linked and recessive, it is never found in females. It is possible for the characteristics to be passed down from mothers to their sons. Iduronate sulphatase is a complicated enzyme that is involved in Hunter's syndrome. This enzyme is responsible for the condition. The absence of this enzyme causes mucopolysaccharides, which are complex sugars, to build up in the organs and tissues of the body. It is these mucopolysaccharides that are responsible for the typical signs and symptoms associated with the syndrome.
• Using techniques that involve sampling of the chorionic villus, it is possible to diagnose Hunter syndrome at about the ninth week of pregnancy.

CHARACTERISTICS

• There are two subtypes of Hunter's syndrome; one of these subtypes is less severe than the other, and its progression is less steep overall.
• The complex sugar that is passed in the urine can be used as a biochemical marker to differentiate between these two different types. The accumulation of this particular sugar in the organs and tissues of the body is what gives rise to the characteristics that are listed below.
• There does not appear to be any issue with the birth of boys affected by Hunter syndrome.
• They do not suffer from any abnormalities in their growth and reach all of their developmental milestones at the appropriate times. During these first few days, the only symptom that may be noticeable is noisy breathing, which is typically accompanied by a stuffy or runny nose. However, because this is typically considered to be a natural and healthy part of childhood, nobody pays attention to the fact that there may be other issues at play. The measurements of the child's head circumference fall within the upper limits of what is considered normal for this age range.
• Umbilical or inguinal hernias are observed in an abnormally high number of infants who are subsequently found to have Hunter syndrome. This is in contrast to the typical incidence of these hernias. Again, boys who do not have Hunter syndrome can still have these weaknesses in the abdominal wall, but because they do not have Hunter syndrome, no one pays attention to them.
• The facial features begin to take on a more angular and coarse appearance somewhere around the age of two and continue to do so well into adulthood. The boy will have a short neck, and his teeth will appear to be coming through at extremely wide intervals when he is an infant. In addition, over the course of the subsequent months, these characteristics are coupled with a deceleration in the rate of growth.
• In addition, it is common to observe the body to be covered with a fine, downy hair, which can cause the joints to become stiff.
• At this point, the accumulation of mucopolysaccharides in the liver and spleen is directly responsible for the enlargement of both of these organs, which takes place at this time. This enlargement may be a contributor to the development of umbilical hernias, as well as their recurrence.
• Children affected by the mild form of Hunter syndrome have normal intelligence or only a very mild intellectual disability, depending on the severity of the condition. Unfortuitously, when it comes to the severe form, the learning disability is more severe and will become apparent at a younger age, somewhere between the ages of eight and ten.
• Deposits of mucopolysaccharides can be found in many organs of the body of the boy as he matures, including the heart valves, coronary arteries, meninges, and joints, to name a few of the possible locations. One or more of these complications will lead to an illness in a boy with Hunter's syndrome, which may have a fatal outcome. This could happen as a result of the boy's condition. For instance, damage to the heart valves and/or coronary arteries can lead to heart failure and, in the case of a blocked coronary artery, can result in an unexpected death.
• Despite the fact that the fundamental genetic and biochemical faults are distinct, the clinical presentation of this condition is strikingly comparable to that of the other mucopolysaccharidoses.

MANAGEMENT IMPLICATIONS

• Unfortunately, there is no treatment that can completely reverse the effects of Hunter's syndrome. The parents require sensitive counseling regarding the future of their son, and it is essential to place emphasis on the assistance that can be provided to make life as normal as possible for both the child and the parents.
• Hernias are a condition that can only be fixed through surgical intervention if the abdominal wall is found to be weak. But (as is the case with Hurler's syndrome), there is a high likelihood of recurrence due to further accumulations of mucopolysaccharides, which increase the pressure inside the abdominal wall and push the contents into weakened areas. This is the same mechanism that causes Hurler's syndrome.
• Children diagnosed with Hunter syndrome need to have their hearing evaluated on a consistent basis. There will need to be distraction tests carried out that are appropriate for the boy's mental age. There is also the possibility of using pure-tone audiometry, with evoked responses serving as an additional diagnostic aid if it is required. Hearing loss is extremely prevalent, and children may require hearing aids as they get older.
• Physiotherapy is an effective method for minimizing joint contractures, which have the potential to severely restrict range of motion if left untreated. The benefits of hydrotherapy, especially its calming effects, are numerous. Ongoing therapy is recommended, and both the mother and the father should be actively involved in their son's care to the greatest extent that is feasible. Joint deformities can sometimes only be corrected successfully through the use of surgical procedures.
• Specialized instruction is required for patients with the severe form of Hunter's syndrome who have learning disabilities. It is necessary to perform regular developmental checks in order to keep track of the boy with Hunter's syndrome and ensure that he is developing normally in all aspects. The findings of such monitoring are required before decisions can be made regarding whether or not special educational facilities are required.
• When dealing with the less severe form of Hunter's syndrome, the typical educational experience is typically satisfactory.

THE FUTURE

• Children who are affected by the severe form of Hunter's syndrome typically only live into their mid-teens to early twenties. When a person is in their early to middle twenties, the most common cause of death is cardiac problems or a severe respiratory infection.
• Those who are affected by the less severe form of Hunter's syndrome tend to live longer, and it is not unheard of for patients to reach their late sixties or even seventies.
• There have been cases of Hunter's syndrome being passed down from fathers to their offspring. Genetic counseling is required for families who have a male child diagnosed with Hunter syndrome. It is possible to identify the females who carry the flawed gene, which is of utmost significance when pondering the possibility of having a child.