Hunter syndrome is a genetic disorder that causes a proteins called glycosaminoglycans (GAGs) to build up in body tissues. This damages the tissues and leads to the symptoms of the disorder.
A person with Hunter syndrome lacks an enzyme known as iduronate 2-sulfatase. When this enzyme is missing, GAGs collect in and damage body tissues.
Types of Hunter syndrome range from mild to severe.
The mild type, which usually is unnoticed until later in life, can cause: heart diseaseshort staturejoint stiffnesshearing impairmentcoarse facial featuresexcess body hair
The severe type of Hunter syndrome shows up in early childhood, and shortens the person's lifespan. It causes the same symptoms as the mild form, but they are more pronounced. In addition, a person with the severe form often has: marked mental retardationphysical deterioration starting early in lifeaggressive behaviorspasticity, or tight muscles that interfere with motor activitieshyperactivity, with constant movement and impulsive behavior
Hunter syndrome is an X-linked recessive disease. This means that the gene that causes it is carried on the X chromosome.
Thus, a male who receives the gene from his mother will be affected. A female can receive the gene either from her father (who has the disease) or from her mother (a carrier). This female, in turn, becomes a carrier herself and can pass the gene to her children.
The syndrome can also occur because of a mutation in a parent's sperm or egg cell.
Genetic counseling may be helpful to couples with a family history of the disease.
A healthcare professional often suspects a person has Hunter syndrome based on his or her physical features. The diagnosis is confirmed either with enzyme studies or by measuring GAGs and other proteins in the urine.
A person with the mild type of Hunter syndrome develops heart disease and deafness, may become immobile because of stiff joints, and may develop degenerative hip disease. A person with the severe type usually does not live past the second or third decade after birth. By then, he or she will have mental retardation and joint stiffness.
Hunter syndrome is not contagious.
A male with Hunter syndrome must pass on the gene to his daughters. However, they are not affected. An affected male cannot pass on the gene to his sons.
A carrier female may pass on the gene to her sons or daughters. Her sons who get the gene will be affected. Her daughters who get the gene will be carriers like her.
Genetic counseling may be useful for affected people and their relatives.
Enzyme replacement therapy may soon be available for this condition. Medications may be used for problems caused by the syndrome, such as heart disease, joint stiffness, hearing impairment, or degenerative joint disease.
Side effects depend on the treatment given.
Medical problems such as heart disease, degenerative joint disease, and hearing impairment can be treated, but will still affect the person's lifestyle.
Hunter syndrome is monitored by regular visits to the healthcare professional, and complications are dealt with as they arise. Any new or worsening symptoms should be reported to the healthcare professional.
Scriver CR et al: The Metobolic and Molecular Basis of Inherited Disease. McGraw-Hill Publishers, 1995
Buyse ML: Birth Defects Encyclopedia. Blackwell Scientific Publications, 1990