Hunter syndrome: A genetic metabolic disorder that arises from deficiency of the enzyme iduronate sulfatase, resulting in tissue deposits of molecules called mucopolysaccharides. The characteristic features of Hunter syndrome include dwarfism, bone deformities, a thickened coarse face, hepatosplenomegaly (enlargement of the liver and spleen) from mucopolysaccharide deposits, cardiovascular disorders from mucopolysaccharide deposits, and deafness. There is no clouding of the cornea.
There are two forms of Hunter syndrome. One is a severe form that causes progressive mental retardation, physical disability, and death before age 15 in most cases. The other is a mild form that is compatible with survival to adulthood and reproduction and in which the intellect is impaired minimally, if at all. Both forms of Hunter syndrome are inherited in an X-linked recessive manner. The gene for iduronate sulfatase is on the X chromosome (in band Xq28).
Bone marrow transplantation has been done without consistently encouraging results. Iduronate sulfatase is currently being tested in enzyme replacement therapy. Hunter syndrome is also known as mucopolysaccharidosis II.