Hunter syndrome overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Hunter syndrome is a lysosomal storage disease caused by a deficient (or absent) enzyme, iduronate-2-sulfatase (I2S). The syndrome is named after physician Charles A. Hunter (1873-1955), who first described it in 1917. Born in Scotland, Hunter emigrated to Canada and had a medical practice in Winnipeg, Manitoba.

Hunter syndrome, or mucopolysaccharidosis II (MPS II), 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.

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. Physical manifestations for some people with Hunter syndrome include distinct facial features, a large head, and an enlarged abdomen. People with Hunter syndrome may also experience hearing loss, thickening of the heart valves leading to a decline in cardiac function, obstructive airway disease, sleep apnea, and enlargement of the liver and spleen. Range of motion and mobility may also be affected. In some cases of Hunter syndrome, central nervous system involvement leads to developmental delays and nervous system problems. Not all people with Hunter syndrome are affected by the disease in exactly the same way, and the rate of symptom progression varies widely. However, Hunter syndrome is always severe, progressive, and life-limiting.