Hunter syndrome pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Hunter syndrome is a serious genetic disorder that primarily affects males. It interferes with the body's ability to break down and recycle specific mucopolysaccharides, also known as glycosaminoglycans or GAG. Hunter syndrome is one of several related lysosomal storage diseases.
Pathophysiology
In Hunter syndrome, GAG build up in cells throughout the body due to a deficiency or absence of the enzyme iduronate-2-sulfatase (I2S).This buildup interferes with the way certain cells and organs in the body function and leads to a number of serious symptoms. As the buildup of GAG continues throughout the cells of the body, signs of Hunter syndrome become more visible.
Genetics
Genetics
Since Hunter syndrome is an inherited disorder (X-linked recessive) that primarily affects males, it is passed down from one generation to the next in a specific way. Nearly every cell in the human body has 46 chromosomes, with 23 derived from each parent. The I2S gene is located on the X chromosome. Females have two X chromosomes, one inherited from each parent, whereas males have one X chromosome that they inherit from their mother and one Y chromosome that they inherit from their father. If a male has an abnormal copy of the I2S gene, he will develop Hunter syndrome. A male can obtain an abnormal copy of the I2S gene in one of two ways. His mother is often a carrier; i.e., she has one abnormal and one normal I2S gene, and she passes along the abnormal gene to him. However, during egg and sperm formation, a mutation can develop in the I2S gene on his X chromosome. In this second case, the mother is not a carrier and the risk of a spontaneous mutation occurring again in a future sibling is low but not zero. Females can carry one abnormal copy of the I2S gene and are usually not affected. Hunter syndrome has been reported to occur in females.