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How is Hunter syndrome inherited?

Hunter syndrome is a genetic disease. In Hunter syndrome, the gene that codes for the enzyme iduronate-2-sulfatase (I2S) contains a mutation (a change), which means that the enzyme is produced with errors that stop it working properly, or the enzyme is not produced at all.

In summary, the gene that causes Hunter syndrome is located on the X chromosome, so a male who inherits an affected chromosome will develop Hunter syndrome. Females have two X chromosomes, so if a female inherits an affected chromosome, in the vast majority of cases, she will not develop the disease, but will be a carrier (i.e. may pass the mutated gene on to her children). This is explained in more detail below.

Learn more about the signs and symptoms of Hunter syndrome

Hunter syndrome family tree

This family tree diagram shows how the gene responsible for Hunter syndrome is inherited and passed on.

Females can carry one Hunter syndrome gene without being affected. If one Hunter syndrome gene is passed onto a male, they will be affected by Hunter syndrome.