The simple detection of neuraminic acid-containing urinary oligosaccharides in patients with glycoprotein storage diseases

Measurement of sialic acid in serum and urine: clinical applications and limitations

Many recent studies have examined the sialic acid content of serum or urine in various pathological states. We have briefly reviewed the substances which contribute to the observed total sialic acid concentration, and given an overview of assay methods used. Three major areas of clinical interest in sialic acid metabolism are discussed. Serum total sialic acid, 'lipid-bound' and 'protein bound' sialic acid have all been proposed as tumour markers; but the usefulness of any of these tests is severely limited by changes due to accompanying inflammatory processes. Serum total sialic acid is not a valuable simple marker of an acute phase response. Urinary free and bound sialic acid measurements should be included in screening protocols for inherited disorders of lysosomal metabolism. Current developments in research and potential applications within the clinical biochemistry laboratory are briefly discussed.

Salla disease in one non-Finnish patient

In a 5-year-old boy, an early onset psychomotor retardation with non-progressive ataxia and without dysmorphic features, associated with lysosomal storage disease found on ultrastructural examination of the conjunctiva, led to the diagnosis of Salla disease. This was supported by a tenfold excretion of urinary free sialic acid, without abnormal oligosacchariduria or anomaly in lysosomal enzymes. This boy is a native of Southern France. Screening of urinary sialic acid has to be introduced in aetiological investigations of patients with apparently non-progressive psychomotor retardation associated with ataxia or dystonic movements.