Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, is a condition that affects many different parts of the body. The condition occurs almost exclusively in boys, although it has been reported in a few girls. It is a progressively debilitating disorder; however, the rate of progression varies among affected individuals.

Variants (also called mutations) in the IDS gene cause MPS II. The IDS gene provides instructions for producing the I2S enzyme, which is involved in the breakdown of large sugar molecules called glycosaminoglycans (GAGs). GAGs were originally called mucopolysaccharides, which is where this condition gets its name.

MPS II occurs in approximately 1 in 100,000 to 1 in 170,000 males.

This condition is inherited in an X-linked recessive pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a variant would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that both copies of a gene would be altered, males are affected by X-linked recessive disorders much more frequently than females. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.

Published Date: October 05, 2023
Published By: National Institutes of Health