What is Hunter Syndrome?

Hunter syndrome is a lysosomal storage disorder caused by a deficiency in the enzyme iduronate-2-sulfatase (I2S). The disease was first described in 1917 by physician Charles A. Hunter (1873-1955), a Scottish national who had a medical practice in Winnipeg, Manitoba. The disease is inherited in an X-linked recessive manner and usually affects males.

What happens in Hunter syndrome?

The I2S enzyme that is deficient in Hunter syndrome is required for the break down and recycling of specific mucopolysaccharides called glycosaminoglycans or GAGs. A deficiency in this enzyme leads to a build up of GAGs in cells throughout the body, which eventually interferes with the function of various tissues and organs. As the cellular GAG accumulation continues over time, the symptoms and complications associated with Hunter syndrome gradually worsen and become more noticeable.

Symptoms of Hunter syndrome

The symptoms of this condition are not present when a child is born, but start to develop after the first year of life. If symptoms start to manifest early (between 2 and 4 years of age), they are generally more severe. One of the first symptoms to develop is often abdominal hernia, which occurs when an abdominal organ or adipose tissue start to protrude through a weakness in the abdominal wall.

Children with the syndrome often share characteristic facial features which include a prominent forehead, a nose that is shallow-bridged and an enlarged tongue. The head and abdomen may also seem larger than usual.

The continued accumulation GAG in cells can eventually affect the function of important organs. The walls of the heart and heart valves thicken which can lead to a decline in cardiac function, for example. The bronchial walls also thicken, which can lead to respiratory complications such as obstructive airway disease.

The accumulation of GAG in the brain can eventually lead to developmental delays and mental retardation. The extent to which function is lost varies between individuals.

Who is affected?

Estimates suggest that Hunter’s syndrome affects around 2,000 people worldwide. About 500 of these sufferers live in the United States. There are 70 patients with the syndrome said to be living in Korea; 30 in Canada; 20 in the Philippines; six in Ireland, two in New Zealand and one in each of Iran, Saudi Arabia, Chile, Israel, India and Pakistan. Reports also suggest that 20 cases exist in Poland. In the UK, the incidence among males is though to be around 1 in 130,000 live births.

Further Reading

Last Updated: Jun 13, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Mandal, Ananya. (2023, June 13). What is Hunter Syndrome?. News-Medical. Retrieved on July 21, 2024 from https://www.news-medical.net/health/What-is-Hunter-Syndrome.aspx.

  • MLA

    Mandal, Ananya. "What is Hunter Syndrome?". News-Medical. 21 July 2024. <https://www.news-medical.net/health/What-is-Hunter-Syndrome.aspx>.

  • Chicago

    Mandal, Ananya. "What is Hunter Syndrome?". News-Medical. https://www.news-medical.net/health/What-is-Hunter-Syndrome.aspx. (accessed July 21, 2024).

  • Harvard

    Mandal, Ananya. 2023. What is Hunter Syndrome?. News-Medical, viewed 21 July 2024, https://www.news-medical.net/health/What-is-Hunter-Syndrome.aspx.


The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.