Hunter syndrome (mucopolysacchridosis II, or MPS II), a progressive disorder arising from a deficiency in the enzyme iduronate sulfatase, is a sex-linked inborn error of metabolism (IEM) affecting only males. The enzyme’s absence or deficiency prevents complete breakdown of the mucopolysacchrides heparen sulphate and dermatan sulfate, which then accumulate in bodily cells. One of a group of lycosomal storage disorders that arise from altered mucopolysaccharide metabolism, Hunter syndrome is of two types, MPS IIA, having severe effects commonly leading to death by age 10-15 years, and MPS IIB, having milder effects and a life span of about 50 years. Collapse of the trachea, cardiac failure, and neurological problems are usual causes of death. In both types, development is apparently normal for about the first two years of life followed by progressive deterioration. Major features of both types are presented here; Pediatric Database (1994) contains a more complete list.
A genetic disorder of the X- linked recessive type, affecting only males, and resulting from a defect in a specific enzyme; one of a group of disorders called mucopolysaccharidoses (MPS). Children affected with MPS II generally have mental retardation, skeletal deformity (especially of the face), retarded growth often resulting in dwarfism, and a shortened life expectancy, often dying in childhood or adolescence, though some with a mild form of the disorder may live a relatively normal life. In addition, the specific characteristics of Hunter’s syndrome include kyphosis (excessive curvature of the spine), ear and hearing problems, and a combination of defects commonly known as gargoylism. Parents with a family history of MPS II may well want to seek genetic counseling before a pregnancy. The defective gene, carried by females and with one chance in two of being passed on to a male child, can be detected by genetic screening tests before pregnancy. Hunter’s syndrome can be detected during pregnancy with prenatal testing, as through amniocentesis, or after birth through urine tests and X-ray analysis of skeletal development.