Mucopolysaccharidosis Type VI

Symptoms

What are the main symptoms of Mucopolysaccharidosis Type VI?

Mucopolysaccharidosis type VI (MPS VI) is a progressive condition, meaning that symptoms will get worse over time, although the speed at which symptoms worsen will vary from person to person. People with MPS VI will usually look normal at birth and won't start showing signs of MPS VI until early childhood. The main symptoms include:

  • skeletal abnormalities - short stature, joint contractures (shortening or hardening of the joints which limits movement), and narrowing of the spinal cord
  • a large head (macrocephaly)
  • too much fluid in the brain (hydrocephalus)
  • distinctive facial features that may be described as "coarse", including a large tongue (macroglossia)
  • heart valve abnormalities
  • an enlarged liver and spleen (hepatosplenomegaly)
  • a soft out-pouching around the belly-button (umbilical hernia) or lower belly (inguinal hernia)
  • a narrow airway which can cause frequent respiratory infections and sleep apnea (when there are pauses in breathing or very shallow breaths during sleep)
  • the cornea (clear covering of the eye) may become cloudy and cause vision loss
  • recurrent ear infections and hearing loss

It is important to note that not all of these symptoms will occur in every individual affected by MPS VI. Also important is the fact that MPS VI does not affect intelligence.

References
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Are there earlier onset, later onset, or variant forms of Mucopolysaccharidosis Type VI?

What health problems should I look for in Mucopolysaccharidosis Type VI?

Any other diseases that look a lot like Mucopolysaccharidosis Type VI (phenocopies, differential diagnoses)?

Are there one or two characteristic "odd" or "unusual" symptoms or clinical features of Mucopolysaccharidosis Type VI?

Is there variable expression or incomplete penetrance in Mucopolysaccharidosis Type VI?

If this is a predisposition gene, what the chances I will get Mucopolysaccharidosis Type VI?

Are there earlier onset, later onset, or variant forms of Mucopolysaccharidosis Type VI?

There is a severe, rapidly progressing form of Mucopolysaccharidosis Type VI (MPS VI), as well as a milder form of the condition. However, an intermediate stage has also been described by scientists so in reality, the forms of MPS VI cannot be separated into groups, but fall along a spectrum.

Urine testing for glycosaminoglycan (GAG) levels, which is what builds up to harmful levels in MPS VI, will generally show that the higher the level, the more severe the symptoms. However, there is currently no definite way to determine how severe someone's symptoms will be by measuring their urine GAG levels. There is also a test that looks at the ARSB gene, which is the gene that is not working properly in MPS VI, to see what kinds of changes or mutations are causing it to not work. Similar to the urine GAG levels, certain gene changes might suggest severe or milder symptoms, but no definite links have been made.

References
What health problems should I look for in Mucopolysaccharidosis Type VI?

In addition to the main health issues in mucopolysaccharidosis type VI (MPS VI):

  • skeletal abnormalities - short stature, joint contractures (shortening or hardening of the joints which limits movement), and narrowing of the spinal cord
  • a large head (macrocephaly)
  • too much fluid in the brain (hydrocephalus)
  • distinctive facial features that may be described as "coarse", including a large tongue (macroglossia)
  • heart valve abnormalities
  • an enlarged liver and spleen (hepatosplenomegaly)
  • a soft out-pouching around the belly-button (umbilical hernia) or lower belly (inguinal hernia)
  • a narrow airway which can cause frequent respiratory infections and sleep apnea (when there are pauses in breathing or very shallow breaths during sleep)
  • the cornea (clear covering of the eye) may become cloudy and cause vision loss
  • recurrent ear infections and hearing loss

Other health problems may include carpal tunnel syndrome, where there is numbness, tingling, or weakness in the hands and fingers. Children may have teeth that are small, widely spaced apart, and have weak enamel (the hard outer layer of the tooth). Their teeth may also have trouble coming through the gums, leading to infections in the mouth.

References
Any other diseases that look a lot like Mucopolysaccharidosis Type VI (phenocopies, differential diagnoses)?

They are several different kinds of mucopolysaccharidosis (MPS) conditions (types I, II, IVA, and VII) that may look similar to MPS type VI because they have similar symptoms early on in life. However, as symptoms progress, it becomes easier to distinguish between the different types. Urine testing for various compounds can also help to narrow down the type of MPS. Some genetic conditions called mucolipidoses may also present similarly to mucopolysaccharidoses. It is important to talk to a doctor who has experience with patients with these conditions in order to be properly diagnosed.

References
  • http://www.ncbi.nlm.nih.gov/books/NBK1162/
  • http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Expert=583
  • Valayannopoulos, V., Nicely, H., Harmatz, P., & Turbeville, S. (2010). Mucopolysaccharidosis VI. Orphanet Journal of Rare Diseases, 5, 5. http://doi.org/10.1186/1750-1172-5-5
Are there one or two characteristic "odd" or "unusual" symptoms or clinical features of Mucopolysaccharidosis Type VI?

The main finding that would distinguish mucopolysaccharidosis type VI (MPS VI) from other genetic conditions that look similar is the presence of dermatan sulfate in the urine without heparan sulfate. People with MPS VI have unique "coarse" facial features from the build up of glycosaminoglycans (GAGs), which causes a thickening of the nose, lips, and tongue. The buildup of GAGs can also cause clouding of the cornea (the clear outer layer) in the eye. However, many of the other symptoms of MPS VI can also be found in conditions within the same family, that is, other types of mucopolysaccharidoses. It is important to note that while some types of mucopolysaccharidoses cause intellectual disability, people with MPS VI usually have normal intelligence.

References
Is there variable expression or incomplete penetrance in Mucopolysaccharidosis Type VI?

Different people with mucopolysaccharidosis type VI (MPS VI) will have different symptoms and different severities of disease. Urine testing for glycosaminoglycan (GAG) levels, which is what builds up to harmful levels in MPS VI, will generally show that the higher the level, the more severe the symptoms. However, there is currently no definite way to determine how severe someone's symptoms will be by measuring their urine GAG levels. There is also a test that looks at the ARSB gene, which is the gene that is not working properly in MPS VI, to see what kinds of changes or mutations are causing it to not work. Similar to the urine GAG levels, certain gene changes might suggest severe or milder symptoms, but no definite links have been made.

References
  • http://ghr.nlm.nih.gov/condition/mucopolysaccharidosis-type-vi
  • Valayannopoulos, V., Nicely, H., Harmatz, P., & Turbeville, S. (2010). Mucopolysaccharidosis VI. Orphanet Journal of Rare Diseases, 5, 5. http://doi.org/10.1186/1750-1172-5-5
If this is a predisposition gene, what the chances I will get Mucopolysaccharidosis Type VI?

Having genetic changes in the ARSB gene associated with mucopolysaccharidosis type VI (MPS VI) is not a predisposition, but a cause of MPS VI. We all have two copies of ARSB in each of our cells and both of these copies need to have changes in order for someone to have MPS VI. If an individual only has changes in one copy, then they are called a carrier and do not have any symptoms. No other conditions are associated with changes in the ARSB gene.

References

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