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SLC17A5 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

SLC17A5 gene

The SLC17A5 gene provides instructions for producing the sialin protein, which is essential for transporting free sialic acid out of cellular compartments called lysosomes.

Normal Function

The SLC17A5 gene provides instructions for producing a protein called sialin. This protein is located on the membranes of lysosomes, which are compartments in the cell that digest and recycle different types of molecules.

Sialin moves (transports) a molecule called free sialic acid to other parts of the cell. Sialic acid is produced when fats and proteins are broken down, and it plays an important role in cell communication and in the attachment of cells to one another (adhesion). Sialic acid is "free" when it is not attached (bound) to other molecules.

Health Conditions Related to Genetic Changes

Free sialic acid storage disorder

Variants (also called mutations) in the SLC17A5 gene have been found to cause free sialic acid storage disorder (FSASD). FSASD is an inherited condition that primarily affects the brain and spinal cord (central nervous system). This condition is often divided into three forms based on the severity of the signs and symptoms.

  • Some SLC17A5 gene variants impair the function of the sialin protein, while others prevent sialin from being produced.
  • In a few cases, sialin is produced but cannot travel to the lysosomal membrane where it is needed.
  • Most SLC17A5 variants replace one protein building block (amino acid) in the sialin protein with another.
  • A particular SLC17A5 variant is found primarily in people from Finland. People from Finland with the least severe form of FSASD (called Salla disease) typically have this variant in both copies of the SLC17A5 gene.
  • The severe form of FSASD is caused by SLC17A5 gene variants that greatly impair the function of sialin protein.
  • Individuals who have one SLC17A5 gene with the Finnish Salla disease variant and one SLC17A5 gene with a variant that causes more severe disease are believed to have the intermediate form of the disorder.

SLC17A5 gene variants that impair or eliminate sialin activity cause free sialic acid to build up in the lysosomes. People with a larger amount of free sialic acid inside the lysosomes typically have more severe signs and symptoms of FSASD, but it is not known exactly how this buildup causes the characteristic features of FSASD.

Other Names for This Gene

  • AST
  • ISSD
  • NSD
  • SD
  • SIALIN
  • SLD
  • solute carrier family 17 (acidic sugar transporter), member 5
  • solute carrier family 17, (sodium phosphate cotransporter), member 5

Frequently Asked Questions

Parents often notice developmental delays, speech difficulties, or motor coordination problems within the first year of life. Some children may also have subtle vision changes or mild hearing loss that become more apparent as they grow. Early neurodevelopmental screening can help flag these issues for further evaluation.
While there is no cure, management focuses on supportive therapies such as physical, occupational, and speech therapy to improve motor and communication skills. Regular monitoring of growth, vision, and hearing is essential, and early intervention can help maximize developmental potential.
Yes, siblings and parents can be tested for carrier status using targeted genetic testing for known SLC17A5 mutations. This is typically done through a blood sample analyzed by a specialized genetics laboratory, and results guide family planning and early screening of future children.
definitive diagnosis usually involves a combination of genetic testing for pathogenic variants in the SLC17A5 gene and biochemical assays that measure free sialic acid levels in blood or urine. Elevated sialic acid concentrations, along with a pathogenic mutation, support the diagnosis.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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