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A Guide to Understanding MPS II (Hunter Syndrome)

key information

source: National MPS Society

year: 2021


MPS II belongs to a group of inherited metabolic diseases called mucopolysaccharidoses (MPS), a subgroup of lysosomal storage disorders (LSDs). MPS is a disorder in which at least one long-chain sugar carbohydrate called glycosaminoglycan, and formerly called mucopolysaccharide accumulates in the lysosome, an organelle within cells. There are seven distinct clinical types of MPS, some of which have several subtypes.

What Causes MPS II?

MPS II is caused by accumulation of two particular GAGs called dermatan sulfate (DS) and heparan sulfate (HS). DS is found in the skin and in the cornea and sclera of the eye, which helps to maintain corneal transparency and the shape of the eye, respectively. DS is also found in high quantities in blood vessel walls, heart valves, tendons, lungs, intestinal mucosa, and the umbilical cord. HS is ubiquitous and is found on the cell surface and in the extracellular matrix. HS is also one of the most complex GAGs in the body. When these GAGs are not degraded, they remain stored inside the cells in the body. The GAGs are not intrinsically toxic, but when they accumulate in large amounts, the effect of storing them in the body can lead to many physical problems. Babies may show little sign of the disease, but as more and more GAGs accumulate, symptoms start to appear as a result of progressive damage.


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