Hunter syndrome is a rare familial disorder in which there is an abnormal buildup of long chain of mucopolysaccharide instead of its breaking down in the body. It is hence also called mucopolysaccharidosis II disease. There is absence of an enzyme called iduronate sulfatase enzyme in this disease. The enzyme is involved in breaking down of mucopolysaccharide. However, without this enzyme the complex form of sugar builds in various organs and tissues of the body.
Usually only boys are affected by this disorder because the defect lies in X chromosome. The syndrome is apparent as early as 18 month to 2 years after birth.Prominent forehead, shallow bridged nose and thick enlarged tongue are apparent features when the child is small, but as age advances other clinical symptoms become more apparent. Hunter syndrome cannot be cured. Treatment is mainly aimed at managing the symptoms and reducing complications.
What Is The Cause Of Hunter Syndrome?
The disease was first identified and described in 1917 by a physician called Charles Hunter. Hunter disease is very rare. The disease affects 1 out of 130000 live births. The disease is present worldwide. Hunter disease is a genetically associated condition. This means defective genes from parents pass on the disease to their children.
It is an X linked inherited condition. Mutation occurs in 12S gene in chromosome X. Each cell has 46 chromosomes, 23 from each parent. In this one pair is X and Y chromosome which gives sexual identity to a person. Female has XX while male has XY chromosome. Hence mutations in fathers chromosome can pass on the condition to a male child while female become only carriers.
The defect leads to lack of an enzyme which is required for breaking of mucopolysaccharide, a type of sugar. Since the sugar is not broken it buildup in different organs and tissues causing substantial damage.
Signs And Symptoms Of Hunter Syndrome
The symptoms of Hunter syndrome become apparent as early as 18 months, predominantly in male child. Following are the signs and symptoms noted Hunter syndrome:
- Abdominal hernia is the first to be apparent. It occurs due to weakness in the abdominal wall.
- Frequent infection in ear and cold are common in the child.
- The symptoms become more apparent as sugar starts to accumulate in the body.
- Facial features are characteristic. The forehead is prominent. The nose is shallow and bridged. Tongue and lips are thick and large.
- Abdomen appears distended due to enlargement of liver and spleen as well as abdominal hernia.
- Stunted growth with delay in development of important milestones such as walking, talking etc.
- The child is hyperactive.
- Small white colored growths on the surface of skin mostly in arms, legs and back.
- Stiffness in joints mainly the elbow, wrist, shoulder, knee and hip. Finger becomes stiff which causes difficulty in grasping any object.
- Buildup of the complex mucopolysaccharide in brain leads to retarded mental growth. The child becomes aggressive.
- Accumulation of complex sugar in various organs causes several complications. For example in heart it can cause thick valves, in lungs it can lead to recurrent respiratory infection, compression of nerve can lead to carpal tunnel syndrome.
Treatment Options For Hunter Syndrome
There is no cure of Hunter syndrome. Treatment is aimed to ease symptoms so that the child can live comfortably as the disease progresses. Recently enzyme replacement therapy has been used in boys suffering from this condition. It helps the child to reduce stiffness, so that the child can walk easily.
Other benefits of enzyme therapy include increase in growth, reduce incidence of respiratory problems. Bone marrow transplant in often tried in early onset disease. Research is also in progress for gene therapy for children suffering from Hunter syndrome.