What else is it called?

  • Mucopolysaccharidosis IX 
  • Natowicz syndrome  
  • Hyaluronidase deficiency 

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What causes it?

MPS IX is caused by a mutation (change) in the HYAL1 gene. This leads to a deficiency in an enzyme called hyaluronidase which is needed to breakdown mucopolysaccharide hyaluronan. When hyaluronan is not broken down entirely, it stays stored in the body. This build-up of hyaluronan in the tissues in the body causes the symptoms associated with the condition. Babies usually show little sign of the condition, but as more and more cells build up, symptoms start to appear.  

How common is it?

MPS IX is an extremely rare condition that was first noted in 1996. Only one case of MPS IX has been reported to date.  

What are the signs and symptoms?

Symptoms of MPS IX may include:  

  • Mild short stature  
  • Cysts  
  • Frequent ear infections  
  • Cleft palate  
  • Flattened nose bridge  
  • Development of soft-tissue masses 

*However, more cases of MPS IX must be identified before a clear clinical picture of symptoms can be established.

How is it diagnosed?

Enzyme assays (testing a range of cells or blood in culture for enzyme deficiency) are used to provide a diagnosis. Individuals with the condition will show a deficiency in the enzyme hyaluronidase.  

Can it be treated?

The treatment for this condition is symptomatic and supportive as there has been no effective drug treatment so far. The aim of this treatment is to manage and alleviate individual symptoms and provide support for the patients and their families.  

Do my family need to be tested?

MPS IX is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents. 

The pattern of inheritance of MPS IX is autosomal recessive. This means that carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with MPS IX are carriers.  

When both parents are carriers, the risk to the baby in each pregnancy is 

  • 25% chance (1 in 4) of developing the condition 
  • 50% chance (1 in 2) for the baby to be a carrier of the condition 
  • 25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier 

Genetic counselling can be requested to get a full explanation.  

Relevant Organisations


References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing [Resource Library No: AAP002]. 

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