Hunter syndrome is a genetic disorder that causes a protein called mucopolysaccharide to build up in body tissues. This damages the tissues and leads to the symptoms.
A person with Hunter syndrome lacks an enzyme known as sulfoiduronate sulfatase. When this enzyme is missing, mucopolysaccharides collect in body tissues, which causes damage.
Hunter syndrome is an X-linked recessive disease. This means that the gene that causes it is carried on the X chromosome. Males who receive the gene from a parent are affected. Females who receive the gene from a parent are not affected and are called carriers. The syndrome can also occur because of a mutation in a parent's sperm or egg cell.