page_title: Hurler syndrome
section_title: Mechanisms
hierarchical_section_title: Hurler syndrome / Mechanisms
context_page_description: Hurler syndrome, also known as mucopolysaccharidosis Type IH, Hurler's disease, and formerly gargoylism, is a genetic disorder that results in the buildup of large sugar molecules called glycosaminoglycans in lysosomes. The inability to break down these molecules results in a wide variety of symptoms caused by damage to several different organ systems, including but not limited to the nervous system, skeletal system, eyes, and heart.
  The underlying mechanism is a deficiency of alpha-L iduronidase, an enzyme responsible breaking down GAGs. Without this enzyme, a buildup of dermatan sulfate and heparan sulfate occurs in the body. Symptoms appear during childhood, and early death usually occurs. Other, less severe forms of MPS Type I include Hurler-Scheie Syndrome and Scheie Syndrome.
  Hurler syndrome is classified as a lysosomal storage disease. It is clinically related to Hunter syndrome; however, Hunter syndrome is X-linked, while Hurler syndrome is autosomal recessive.
context_section_description: The IDUA gene is responsible for encoding an enzyme called alpha-L-iduronidase. Through hydrolysis, alpha-L-iduronidase is responsible for breaking down a molecule called unsulfated alpha-L-iduronic acid. This is a uronic acid found in the GAGs dermatan sulfate and heparan sulfate. The alpha-L-iduronidase enzyme is located in lysosomes. Without sufficient enzymatic function, these GAGs cannot be digested properly.
caption: Heparan sulfate is one of the GAGs that builds up in the lysosomes of people with Hurler Syndrome