A type of lysosomal storage disease that is often caused by a deficiency of iduronate-2-sulfatase resulting in the accumulation of mucopolysaccharides (particularly, heparan sulfate and dermatan sulfate)
Lysosomal storage disease is a collective term for the various metabolic disorders due to defects in lysosomal function resulting in an abnormal accumulation of toxic materials in the cell. One of them is mucopolysaccharidosis, a condition due to the accumulation of mucopolysaccharides (now referred to as glycosaminoglycans) in the lysosomes.
Hunter syndrome is a genetic condition that is caused by a pathological mutation in the IDS gene located on the X chromosome. Thus, this condition may be inherited as an X-linked trait. As an X-liked disease, the Hunter syndrome affects mostly the males since they would have only one X chromosome. The male offspring with a defective copy of the IDS gene in the X chromosome would tend to have a deficiency of iduronate-2-sulfatase. This enzyme is important in catalyzing the breakdown of dermatan sulfate and heparan sulfate. Without this enzyme, these mucopolysaccharides accumulate within the lysosomes. This causes damage and leads to symptoms associated with Hunter syndrome. These symptoms are coarse facial features, short stature, skeletal dysplasia, retinitis pigmentosa, hepatosplenomegaly, neurologic deterioration, and death in childhood. It is often distinguished clinically from hurler syndrome by the absence of corneal clouding. Milder forms allow for survival to adulthood with minimal neurologic problems. Patients have the two types of sulfates in their urine. A variety of point mutations, splicing defects and deletions have been found in the gene, with full deletions causing the most severe disease. At present, there is no cure to Hunter syndrome.
Hunter syndrome is named after Charles A. Hunter, the Scottish-born Canadian physician in 1917.
- mucopolysaccharidosis type II