Hunter Syndrome: Causes, Symptoms, Diagnosis, Treatment

Hunter Syndrome is the term given to a significantly rare genetic medical condition in which an enzyme called iduronate-2-sulfatase, Which facilitates breakdown of a form of sugar called glycosaminoglycans is either entirely missing from the body or is malfunctioning as a result of which there is excessive build up of glycosaminoglycans causing a variety of symptoms. Some of the symptoms caused by Hunter Syndrome are inappropriate appearance, lack of adequate development of the brain, organ dysfunction, etc. The symptoms of Hunter Syndrome can be observed as early as infancy and mostly found in males. Hunter Syndrome cannot be cured and treatment is primarily aimed at controlling the symptoms and complications that arises from this disease.

As stated, Hunter Syndrome is caused due to missing or malfunctioning enzyme called iduronate-2-sulfatase which facilitates breakdown of glycosaminoglycans. The chromosome which causes malfunctioning of the enzyme is usually inherited from the mother. This enzyme is usually present in the lysosomes. Under normal circumstances, the nutrients present in the body are broken down by lysosomes to build healthy tissues, bones, cartilage etc. When iduronate-2-sulfatase does not function adequately it results in gradual buildup of glycosaminoglycans causing Hunter Syndrome.

• Development delays
• Thickened lips or nostrils
• Broad nose
• Claw-like hands
• Protruding tongue
• Skeletal deformities
• Hepatomegaly
• Splenomegaly
• Sleep apnea
• Persistent hypertension
• Vision impairment
• Progressive hearing loss
• Behavioral disorder
• Joint stiffness
• Diarrhea.

The first sign of Hunter Syndrome is a visible change in facial features of the baby. In order to confirm the diagnosis of Hunter Syndrome, the treating physician will order blood or urine tests to see if the levels of glycosaminoglycans are elevated. Additionally, a genetic analysis will also be done in order to confirm the diagnosis of Hunter Syndrome. There have been instances when Hunter Syndrome has been diagnosed when testing is being conducted to rule out some other medical condition such as testing done to find out the cause of recurrent pneumonia in a child. In this, a chest x-ray will reveal irregularly shaped vertebrae, which is a classic sign of Hunter Syndrome.

Hunter Syndrome has no cure. The treatment is basically aimed at controlling the symptoms and managing the complications of the disease so as to give relief. However, there are some treatments that are coming up for Hunter Syndrome. Some of the treatments are:

• Bone Marrow Transplantation: This method of treatment can be used for mild forms of Hunter Syndrome and has shown to be effective. This treatment controls difficulty breathing, facilitates better mobility, and also improves cardiac, liver, and spleen function. It also helps with improvement of mental function of the child.
• Enzyme Therapy: This mode of treatment utilizes genetically engineered enzymes to replace the missing or malfunctioning enzymes and has shown to delay the progress of the disease significantly. This therapy is given intravenously once a week, although it is yet to be seen if this form of treatment is good enough to improve the quality of life of an affected individual and it also carries with it potential complications like allergic reactions, fevers, headaches, etc.
• Gene Therapy: This mode of therapy replaces the offending chromosome which is responsible for malfunctioning of the enzyme but the success rate of this treatment is still a matter of ongoing research.

Hunter Syndrome is an inherited medical condition hence genetic counseling is imperative if an individual is found to be a carrier of the defective chromosome before planning to have children. This is by far the best way to prevent Hunter Syndrome.