Hurler syndrome overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2]
Overview
Hurler syndrome, also known as mucopolysaccharidosis type I (MPS I), Hurler's disease and gargoylism[1], is a genetic disorder that results in the deficiency of alpha-L iduronidase, which is an enzyme that breaks down mucopolysaccharides. Without this enzyme, the buildup of heparan sulfate and dermatan sulfate occurs in the body (the heart, liver, brain etc.). Symptoms appear during childhood and early death can occur due to organ damage.
Classification
MPS I is divided into three subtypes based on severity of symptoms. All three types result from an absence of, or insufficient levels of, the enzyme alpha-L-iduronidase. MPS I H or Hurler syndrome is the most severe of the MPS I subtypes. The other two types are MPS I S or Scheie syndrome and MPS I H-S or Hurler-Scheie syndrome.
Pathophysiology
Children born to an MPS I parent carry a defective IDUA gene, which has been mapped to the 4p16.3 site on chromosome 4. The gene is named IDUA because of its iduronidase enzyme protein product. As of 2001, 52 different mutations in the IDUA gene have been shown to cause Hurler syndrome.
Causes
Persons with Hurler syndrome do not make a substance called lysosomal alpha-L-iduronidase. This substance, called an enzyme, helps break down long chains of sugar molecules called glycosaminoglycans (formerly called mucopolysaccharides). These molecules are found throughout the body, often in mucus and in fluid around the joints.
Epidemiology and Demographics
Hurler syndrome has an overall frequency of 1 per 115,000 population.
Natural History, Complications and Prognosis
Children with Hurler syndrome often die before age 10 from obstructive airway disease, respiratory infections, or cardiac complications. Hurler syndrome is a disease with a poor outlook. Children with this disease develop nervous system problems, and can die young.
Diagnosis
History and Symptoms
Affected children may be quite large at birth and appear normal but may have inguinal (in the groin) or umbilical (where the umbilical cord passes through the abdomen) hernias. Growth in height may be initially faster than normal, then begins to slow before the end of the first year and often ends around age 3. Many children develop a short body trunk and a maximum stature of less than 4 feet. Distinct facial features (including flat face, depressed nasal bridge, and bulging forehead) become more evident in the second year. By age 2, the ribs have widened and are oar-shaped. Children may experience noisy breathing and recurring upper respiratory tract and ear infections. Feeding may be difficult for some children, and many experience periodic bowel problems.
Treatment
References
- ↑ Gargoylism. gpnotebook.co.uk. URL: http://www.gpnotebook.co.uk/cache/1644560391.htm. Accessed on: April 29, 2007.