Hunter syndrome is clinically linked to hurler syndrome. Hurler syndrome is an autosomal recessive disorder whereas hunter syndrome is an x-linked disorder. To understand the differences between Hunter syndrome and hurler syndrome, let us have a look at both disorders-

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Hunter Syndrome VS Hurler Syndrome

Hunter syndrome and Hurler syndrome present with many common signs and symptoms. However, the major difference lies between the origin of the disorders and also symptoms like corneal clouding, which is a characteristic of Hurler syndrome and all other MPS I syndromes and not of Hunter syndrome or any other MPS II syndromes. (1)

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Hunter Syndrome

  • Hunter syndrome is a genetic disorder, which is inherited and quite rare
  • It is caused due to an enzyme called iduronate 2 sulfatase, which is either malfunctioning or missing altogether
  • This enzyme breaks down some complex molecules. If this enzyme is not present in enough quantities, these complex molecules start collecting in harmful quantities, giving rise to hunter syndrome
  • There is a permanent damage to the body, which is progressive in nature and causes issues with appearance, organ functioning, physical and mental growth and development (3)
  • Hunter syndrome is much common in boys than girls
  • Hunter syndrome cannot be cured
  • The signs and symptoms of hunter syndrome range from mild to severe
  • They are not seen at birth, but gradually develop as the child reaches ages 2 to 4 years
  • The signs and symptoms may consist of an enlarged head, thick lips, mouth that often stays open with a protruding tongue, a big and broad nose, a hoarse voice, skeletal irregularities, enlarged internal organs resulting in a distended abdomen, joint stiffness, behavioral aggression, stunted or slow growth, slow or late physical and mental development
  • There is no corneal clouding as in MPS I syndromes- one of which is hurler syndrome
  • Hunter syndrome occurs when a mother passes a defective chromosome to her child, which means it is an X-linked disorder and the only one of MPS syndromes which is an x-linked disorder
  • Usually, the average life expectancy is 20 to 30 years for mild cases and teenage years for severe cases

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Hurler Syndrome

  • Hurler syndrome is a rare genetic disorder
  • It is caused due to an enzyme called alpha-L iduronidase, which is either malfunctioning or totally absent
  • This enzyme is responsible for the breaking up of dermatan sulfate and heparan sulfate in the body
  • Without the help of this enzyme, these complex molecules start building up in harmful amounts in the body, giving rise to hurler syndrome (2)
  • In this disorder, a progressive and permanent damage occurs in the body, which causes problems with the appearance, organ functioning, physical and mental growth and development
  • The children diagnosed with hurler syndrome appear to be perfectly normal at birth. Symptoms start settling in slowly thereafter
  • The first signs that may be noticed in hurler syndrome are misformation of facial features. This can be seen mostly at around 3 to 6 months of age
  • The head is enlarged, with a prominent bone structure, the nose may be broad and flat, eyes may appear to be bulging out from the skull, lips can be large and the jaws can be in a dropped position continuously, spine and skeletal deformities can start to set in by the age of 6 months but can be clinically seen only after about 12-14 months. There may be a stunted growth by the age of 2 years and the overall height reached is not more than 4 feet on an average. Development of hernias, corneal clouding and retinal degeneration are yet other symptoms. The internal organs become quite enlarged. Deterioration follows soon after the age of 4 years and is progressive thereafter.
  • Average life expectancy in hurler syndrome is of about 10 years
  • Hurler syndrome cannot be cured
  • Bone marrow transplant may increase the life span by a few years
  • Hurler syndrome is an autosomal recessive disorder

References-

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3249184/
  2. https://en.wikipedia.org/wiki/Hurler_syndrome
  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3361789/

Also Read:

Pramod Kerkar

Written, Edited or Reviewed By:

, MD,FFARCSI

Pain Assist Inc.

Last Modified On: April 19, 2019

This article does not provide medical advice. See disclaimer

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