Type II - Hunter syndrome

It affects mainly boys. Type II accounts for about 20% of all mucopolysaccharidoses cases. In Poland one girl has been diagnosed with Hunter syndrome.

Hunter syndrome shows X-linked recessive inheritance. Mothers pass the defective gene to a son except very rare cases when also girls are affected by the disorder. Worldwide there are 13 diagnosed cases of incidence in girls including one case in Poland. Boys receive the Y chromosome from their father and have only one X chromosome inherited from their mother. A woman who carries the Hunter syndrome gene has one normal and one defective chromosome X. If she passes along the defective gene to son, he will not have any genes with the correct information concerning enzyme production and will be affected by Hunter syndrome. If a mother carries the defective gene there is a one in two chance that a son will suffer from the disorder. The risk of having an affected baby by a mother's sisters and sisters of her mother is also 50%.

There are two clinical subtypes of the disorder.

Type A – severe

A severe form. According to international statistics it affects about 84% of the patients diagnosed with Hunter syndrome. It shows symptoms typical of mucopolysaccharidosis such as:

  • skeletal changes (enlarged flat bones and shorthened deformed long bones)
  • enlarged liver
  • heart defects
  • joint stiffness
  • mental retardation
  • coarse facial features
  • short stature
  • umbilical and inguinal hernias
  • hearing impairment

Type B – mild

The patient's body produces residual quantities of the iduronate sulfatase enzyme. The skeletal irregularities are less evident; either there is no mental retardation or it is moderate, bone changes are far less accentuated.

Deficient enzyme : iduronate sulfatase

The enzyme is required to break down substances called glycosaminoglycans (GAG). Since patients affected by Hunter syndrome cannot break these substances down, glycosaminoglycans gradually collect in different organs resulting in their damage.


On 8 January 2007 the European Commission approved the Elaprase formulation as a treatment for MPS Type II in the European Union. Since 24 November 2008 patients suffering from mucopolysaccharidosis type II have had access to long-term enzyme replacement therapy with Elaprase, which a synthetic version iduronate sulfatase. Thanks to this therapy the symptoms of the disorder are alleviated. Since the treatment has not been in use long enough, the research on long-term effects of the therapy is in progress.

Without the treatment patients affected by the severe form usually did not live into the second decade

© Przemysław Racinowski