Diagnostic challenges in Salla disease

Sialic acid storage disease (Salla disease) is an autosomal recessive disorder caused by mutations in a lysosomal sialic acid export protein, SLC17A5 (OMIM #604369). This disorder was initially described in Northern Finland but more recently has been reported in patients of other ethnicities. We describe the clinical presentation and the neuroimaging findings of two non-Finnish children where a diagnosis of Salla disease was suspected on the basis of brain magnetic resonance imaging. The biochemical confirmation of this diagnosis posed a challenge as both patients had elevated percent free urine sialic acid but biochemical analyses in fibroblasts were not conclusive; therefore, molecular testing was necessary for confirmation of the diagnosis. The described encounters demonstrate the importance of pursuing confirmatory molecular diagnostic testing when a sialic acid storage disorder is suspected.