Sialuria

What is sialuria?

Sialuria is a rare disorder that has variable effects on development. Affected infants are often born with a yellow tint to the skin and the whites of the eyes (neonatal jaundice), an enlarged liver and spleen (hepatosplenomegaly), and unusually small red blood cells (microcytic anemia). They may develop a somewhat flat face and distinctive-looking facial features that are described as "coarse." Temporarily delayed development and weak muscle tone (hypotonia) have also been reported.

Young children with sialuria tend to have frequent upper respiratory infections and episodes of dehydration and stomach upset (gastroenteritis). Older children may have seizures and learning difficulties. In some affected children, intellectual development is nearly normal.

The features of sialuria vary widely among affected people. Many of the problems associated with this disorder appear to improve with age, although little is known about the long-term effects of the disease. It is likely that some adults with sialuria never come to medical attention because they have very mild signs and symptoms or no health problems related to the condition.

How common is sialuria?

Fewer than 10 people worldwide have been diagnosed with sialuria. There are probably more people with the disorder who have not been diagnosed, as sialuria can be difficult to detect because of its variable features.

What genes are related to sialuria?

Mutations in the GNE gene cause sialuria. The GNE gene provides instructions for making an enzyme found in cells and tissues throughout the body. This enzyme is involved in a chemical pathway that produces sialic acid, which is a simple sugar that attaches to the ends of more complex molecules on the surface of cells. By modifying these molecules, sialic acid influences a wide variety of cellular functions including cell movement (migration), attachment of cells to one another (adhesion), signaling between cells, and inflammation.

The enzyme produced from the GNE gene is carefully controlled to ensure that cells produce an appropriate amount of sialic acid. A feedback system shuts off the enzyme when no more sialic acid is needed. The mutations responsible for sialuria disrupt this feedback mechanism, resulting in an overproduction of sialic acid. This simple sugar builds up within cells and is excreted in urine. Researchers are working to determine how an accumulation of sialic acid in the body interferes with normal development in people with sialuria.

Read more about the GNE gene.

How do people inherit sialuria?

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Most reported cases have occurred in people with no known history of the disorder in their family and may result from new mutations in the gene.

Where can I find information about treatment for sialuria?

These resources address the management of sialuria and may include treatment providers.

• Gene Review: Sialuria
• MedlinePlus Encyclopedia: Hepatosplenomegaly (image)
• MedlinePlus Encyclopedia: Newborn Jaundice

You might also find information on treatment of sialuria in Educational resources and Patient support.

Where can I find additional information about sialuria?

You may find the following resources about sialuria helpful. These materials are written for the general public.

• MedlinePlus - Health information (3 links)
• Educational resources - Information pages (3 links)
• Patient support - For patients and families (3 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

• Gene Reviews - Clinical summary
• Gene Tests - DNA tests ordered by healthcare professionals
• PubMed - Recent literature
• Online Books - Medical and science texts
• Scriver's Online Metabolic and Molecular Bases of Inherited Disease (OMMBID): Disorders of Free Sialic Acid Storage
• OMIM - Genetic disorder catalog

What other names do people use for sialuria?

• French type sialuria
• Sialuria, French type

See How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about sialuria?

• See How can I find a genetics professional in my area? in the Handbook.
• Ask the Genetic and Rare Diseases Information Center.
• Submit your question to Ask the Geneticist.

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

• What does it mean if a disorder seems to run in my family?
• What are the different ways in which a genetic condition can be inherited?
• If a genetic disorder runs in my family, what are the chances that my children will have the condition?
• Why are some genetic conditions more common in particular ethnic groups?

These links provide additional genetics resources that may be useful.

• Genetics and health
• Resources for Patients and Families
• Resources for Health Professionals

What glossary definitions help with understanding sialuria?

acids ; anemia ; autosomal ; autosomal dominant ; cell ; dehydration ; enzyme ; gene ; hepatosplenomegaly ; hypotonia ; infection ; inflammation ; jaundice ; microcytic anemia ; molecule ; muscle tone ; mutation ; neonatal ; new mutation ; red blood cell ; respiratory ; seizure ; sialic acid ; sign ; simple sugar ; stomach ; symptom ; tissue

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

See also Understanding Medical Terminology.

References

These sources were used to develop the Genetics Home Reference condition summary on sialuria.

• Enns GM, Seppala R, Musci TJ, Weisiger K, Ferrell LD, Wenger DA, Gahl WA, Packman S. Clinical course and biochemistry of sialuria. J Inherit Metab Dis. 2001 Jun;24(3):328-36. PubMed citation
• Gene Review: Sialuria
• Leroy JG, Seppala R, Huizing M, Dacremont G, De Simpel H, Van Coster RN, Orvisky E, Krasnewich DM, Gahl WA. Dominant inheritance of sialuria, an inborn error of feedback inhibition. Am J Hum Genet. 2001 Jun;68(6):1419-27. Epub 2001 Apr 18. PubMed citation
• Seppala R, Lehto VP, Gahl WA. Mutations in the human UDP-N-acetylglucosamine 2-epimerase gene define the disease sialuria and the allosteric site of the enzyme. Am J Hum Genet. 1999 Jun;64(6):1563-9. PubMed citation
• Strehle EM. Sialic acid storage disease and related disorders. Genet Test. 2003 Summer;7(2):113-21. Review. PubMed citation