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What is Hunter syndrome?

Learn more about the signs and symptoms of Hunter syndrome

What causes Hunter syndrome?

Hunter syndrome is one of a number of lysosomal storage diseases (LSDs). LSDs are conditions in which cells are unable to properly break down certain molecules. In Hunter syndrome, an enzyme called iduronate-2-sulfatase (I2S) is deficient or sometimes completely absent.

In a healthy cell, I2S breaks down particular molecules, known as glycosaminoglycans (GAGs). These molecules were previously called mucopolysaccharides, which is why Hunter syndrome is also known as mucopolysaccharidosis type II (MPS II).

If I2S is deficient or absent, GAGs build up, which prevents the cell from functioning properly. All healthy cells (except red blood cells) make the I2S enzyme, so its deficiency can affect any part of the body. This is why Hunter syndrome may have symptoms in several organs, and is called a multisystemic disease.

Learn more about the early signs and symptoms that each of these patients experienced

Discussing Hunter syndrome with your child’s doctor is a resource that may help you talk to your doctor about your child’s symptoms.