Hunter syndrome is a very rare, progressive and life threatening disease that primarily affects males. It is one of several related lysosomal storage diseases.
Individuals with Hunter syndrome lack the enzyme iduronate-2-sulfatase (I2S), which is essential in the continuous breaking down and recycling of complex carbohydrates called mucopolysaccharides, also known as glycosaminoglycans (GAG). Life expectancy for severely affected patients is only 10 to 20 years.
In Hunter syndrome, GAG build up in cells interferes with the way certain cells and organs in the body function and leads to a number of serious symptoms. Physical manifestations for some people with Hunter syndrome include distinct facial features, a large head, an enlarged abdomen and joint problems. 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.
Not all people with Hunter syndrome are affected by the disease in exactly the same way, and the rate of symptom progression varies widely from patient to patient. Indeed some people who have Hunter syndrome can live into their 20s or 30s; there are occasional reports of people who have lived into their 50s or 60s. Their quality of life can remain high and they can remain actively employed. In contrast, many others with Hunter syndrome develop severe impairments and can have life expectancies of 15 years or less.
Hunter syndrome affects a calculated estimate of approximately 1 in 155,000 live male births, and affects an estimated 30 to 40 people in Canada.