Sialuria

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Sialuria is caused by mutations (changes) in the GNE gene. This gene provides instructions for making an enzyme found in cells and tissues throughout the body. This enzyme is responsible for producing sialic acid which is a simple sugar that attaches to the ends of more complex molecules on the surface of the cells. By changing these molecules, sialic acid affects several cell functions such as cell movement, attachment of cells to cells and signalling between cells.  

The enzyme produced by the GNE gene is controlled to make sure that the cells produce a suitable amount of sialic acid. A feedback system is responsible for shutting off the enzyme when no more sialic acid is needed. In individuals with sialuria, the mutations disturb this feedback system which leads to an overproduction of sialic acid. The simple sugar will build up within the cells and is released in the urine. It is still unclear how the build up of sialic acid in the body causes the symptoms associated with sialuria.  

Sialuria is an extremely rare inherited condition. Less than 10 people have been diagnosed with sialuria worldwide. It is likely that more people have the condition but have not been diagnosed because sialuria can be difficult to detect due to its varying features.  

Symptoms vary widely in individuals affected and not all patients will display all the symptoms listed below.  

Possible symptoms in infants: 

• Neonatal jaundice (yellow tint to the skin and white of the eyes) 
• Hepatosplenomegaly (enlarged liver and spleen) 
• Microcytic anaemia (small red blood cells)  
• “coarse” facial features  
• Temporarily delayed development  
• Hypotonia (weak muscle tone) 

Symptoms in children:  

• Frequent upper respiratory infections  
• Episodes of dehydration  
• Gastroenteritis (stomach upset)  
• Seizures  
• Learning difficulties  

Many of the symptoms of this condition improve with age, however, little is known about the long term affects of sialuria. Some adults with sialuria do not need medical attention as they have very mild symptoms and no health problems related to the condition.  

The diagnosis of this condition usually starts by detecting several symptoms in infants or young children including:  

• Mild facial coarsening 
• Hypotonia (weak muscle tone)  
• developmental delay 
• Frequent upper respiratory infections 

This is usually followed by specialised urine tests which will detect the highly raised excretion of sialic acid in the urine.  

The diagnosis can be confirmed through molecular genetic testing by identifying mutations in the GNE gene.

Treatment for this condition is symptomatic and supportive. This aims to manage and alleviate individual symptoms such as treatment for jaundice, and to provide support for the patients and their families.  

Sialuria 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 sialuria is autosomal dominant. This means that one copy of the altered gene in each cell is enough to cause the disorder. Cases can occur in people with no known family history of the disorder as it can result from a new mutation in the gene. Spontaneous mutations happen during the formation of a egg or sperm cell or during the development of the embryo.  

A person affected by an autosomal dominant disorder such as sialuria has a 50% chance of passing the mutated gene to each child. There is also a 50% chance that the child will not inherit the mutated gene.  

Genetic counselling can be requested to get a full explanation. 

References are available on request. Please contact us on 0800 652 3181 or by emailing contact@metabolicsupport.org.

Please note calls to 0800 numbers are free from UK landlines and mobiles. Calls from business lines may be charged – please check with your provider.

This information about metabolic diseases is provided by Metabolic Support UK and is intended for educational purposes only. It should not be used for diagnostic or treatment purposes.

Should you require more detailed information please contact Metabolic Support UK by email (contact@metabolicsupport.org) or by telephone ( 0800 652 3181). For specific medical information regarding a disorder or individual please contact your GP or Paediatrician. Metabolic Support UK accepts no responsibility for any errors or omissions nor does Metabolic Support UK assume any liability of any kind for the content of any information contained within this summary or any use that you may make of it.