MPS II (Hunter Syndrome) is a Lysosomal Storage Disease (LSD) that inhibits the body’s ability to break down and recycle specific mucopolysaccharides (mew-ko-pol-ee-sak-ah- rides). It is part of a larger group of conditions called Mucopolysaccharidosis (MPS), of which there are multiple variations and a whole spectrum of severities.
Lysosomal Storage Diseases
There are 49 genetic Lysosomal Storage Diseases – or conditions that are characterized by a deficiency of one or more of the lysosomal enzymes that the body requires to digest material inside the lysosome. This deficiency results in a build up of undigested material inside the lysosome, which leads to cell degeneration, causing macromolecules in various organs and tissues in the body. In time, and the time varies depending on the severity of the case, this leads to decreased function in the affected areas, progressive deterioration in the physical and/or mental capacity of the individual, and eventual death. Click here for more information on LSDs.
MPS II is caused by a missing enzyme called iduronate sulfatase (I2S). The lysosomal enzyme I2S is critical in the breakdown of two specific mucopolysaccharides: dermatan sulfate and heparan sulfate. Mucopolysaccharides are the result of the body breaking down and replacing proteoglycans, which exist in the connective tissues throughout the body. When the body of a person with MPS II breaks down proteoglycans, it is not able to recycle dermatan sulfate and heparan sulfate, resulting in a accumulation of these mucopolysaccharides (also known as glycosaminoglycans or GAGs) in the body. These particular mucopolysaccharides are most prevalent in a person’s skin, blood vessels, heart, heart valves, lungs, arteries and cell surfaces. MPS II is progressive, because as the build up continues over time, it interferes with certain cells and organs ability to function.
And in English
MPS II is characterized by the build up of GAGs in the body which interfere with cells and organs ability to function. A child with MPS will appear healthy at birth. The symptoms will become evident as the buildup occurs, and will worsen overtime, as it continues.