Primary solute translocator for anionic substances; particularly it is a free sialic acid transporter in the lysosomes (Probable). Defects in SLC17A5 are the cause of Salla disease (SD); also known as Finnish type sialuria. SD is a sialic acid storage disease (SASD). SASDs are autosomal recessive neurodegenerative disorders characterized by hypotonia, cerebellar ataxia and mental retardation. They are caused by a defect in the metabolism of sialic acid which results in increased urinary excretion of unconjugated sialic acid, specifically N- acetylneuraminic acid. Enlarged lysosomes are seen on electron microscopic studies. Clinical symptoms of SD present usually at age less than 1 year and progression is slow. Defects in SLC17A5 are the cause of infantile sialic acid storage disorder (ISSD); also known as N- acetylneuraminic acid storage disease (NSD). ISSD is a severe form of sialic acid storage disease. Affected newborns exhibit visceromegaly, coarse features and failure to thrive immediately after birth. These patients have a shortened life span, usually less than 2 years. Infantile sialic acid storage disorder is associated with non-immune hydrops fetalis, a generalized edema of the fetus with fluid accumulation in the body cavities due to non-immune causes. Non-immune hydrops fetalis is not a diagnosis in itself but a symptom, a feature of many genetic disorders, and the end- stage of a wide variety of disorders. Belongs to the major facilitator superfamily. Sodium/anion cotransporter family. 2 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.