Mucopolysaccharidosis type IVB

Overview

What is mucopolysaccharidosis type IVB?

Mucopolysaccharidosis type (MPS) IVB is a rare genetic disorder. This means that people have a problem in a specific gene. People have about 20,000-25,000 genes in their bodies. Genes are like our body's instruction manual - they control the growth, development and normal function of the body. Because of a change in a specific gene, people with MPS IVB lack an enzyme. This enzyme is needed to break down (metabolize) certain complex substances in the body. Without this enzyme, people cannot break down certain large sugar molecules. These molecules build up in the tissues, bones and major organs of the body. Eventually this damages the affected area and organs. People with MPS IVB can have lots of problems. They can have skeleton, heart, vision and dental problems, hearing loss, growth deficiency and short stature. People can have different symptoms and the symptoms that occur can be mild or severe. The brain is not affected and people usually have normal intelligence and generally have no issues with thinking or learning. However, some children can have delays in reaching developmental milestones or learning disabilities because of certain symptoms, particularly spinal problems, related to this disorder. There are two types of MPS IV: type IVA and type IVB. Type IVA is caused by alterations (mutations) in the GALNS gene. Type IVB is caused by alterations in the GLB1 gene. Generally, children with MPS IVB have less severe symptoms than children with MPS IVA, but this is not always the case as the severity of these disorders can vary greatly among affected people.

References
  • Froissart R, Marie I. Mucopolysaccharidosis type 4. OrphaNet website. Accessed February 2, 2016. http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=582
  • Regier DS, Tifft CJ. GLB1-Related Disorders. GeneReviews website. Accessed February 2, 2016. https://www.ncbi.nlm.nih.gov/books/NBK164500/
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Are there other names for mucopolysaccharidosis type IVB?

How common is mucopolysaccharidosis type IVB?

What is the difference between mucopolysaccharidosis MPS IVB and MPS IVA?

Are there other names for mucopolysaccharidosis type IVB?

There are several names that are used to described mucopolysaccharidosis type IVB. These other names are:

  • MPS IVB
  • MPS type IVB
  • Mucopolysaccharidosis IVB
  • Morquio disease B
  • Morquio disease type B
  • Morquio syndrome B
  • Morquio syndrome type B
References
  • Mucopolysaccharidosis IV. The National Organization for Rare Disorders website. Accessed February 2, 2016. https://rarediseases.org/rare-diseases/morquio-syndrome/
  • Froissart R, Marie I. Mucopolysaccharidosis type 4. OrphaNet website. Accessed February 2, 2016. http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=582
How common is mucopolysaccharidosis type IVB?

Mucopolysaccharidosis type (MPS) IVB is a rare disorder. Rare disorders often go unrecognized or misdiagnosed and the incidence and prevalence of individual rare disorders is often unclear or unknown. Prevalence is the measurement of all individuals affected by the disease at a particular time. Incidence is the number of new people with a disorder or newly-diagnosed in a given year. There have been several studies in specific populations. One estimate places the prevalence of MPS IVB anywhere from 1 in 250,000 to 1,000,000 million people. MPS IVB is much rarer than MPS IVA.

References
  • Regier DS, Tifft CJ. GLB1-Related Disorders. GeneReviews website. Accessed February 2, 2016. https://www.ncbi.nlm.nih.gov/books/NBK164500/
  • Mucopolysaccharidosis type IV. Genetics Home Reference website. Accessed February 2, 2016. https://ghr.nlm.nih.gov/condition/mucopolysaccharidosis-type-iv
What is the difference between mucopolysaccharidosis MPS IVB and MPS IVA?

Mucopolysaccharidosis (MPS) IV is broken down into two different disorders. Type A and Type B. They are also called Morquio syndrome A and Morquio syndrome B. Doctors once believed that these were the same disorder. However, doctors now know that the disorders are caused by changes (mutations) in different genes, which affect different enzymes. These enzymes are important for breaking down keratan sulfate and chondroitin 6-sulfate, types of glycosaminoglycans (which are sugar molecules that use to be called mucopolysaccharides). Although the symptoms are very similar, it is important to distinguish between these disorders as the treatments will be different.

MPS IVB is also related to a disorder called GM1 gangliosidosis. Both disorders are caused by changes (mutations) in the same gene, called GBL1. They are sometimes grouped together as GBL1-related disorders.

References
  • Regier DS, Tifft CJ. GLB1-Related Disorders. GeneReviews website. Accessed February 2, 2016. https://www.ncbi.nlm.nih.gov/books/NBK164500/
  • Mucopolysaccharidosis IV. The National Organization for Rare Disorders website. Accessed February 2, 2016. https://rarediseases.org/rare-diseases/morquio-syndrome/

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