Generalized N-acetylneuraminic acid storage disease: quantitation and identification of the monosaccharide accumulating in brain and other tissues.

Brain and other tissues from a patient with extensive neonatal ascites and clinical symptoms suggestive of a severe neurovisceral storage disorder were examined following autopsy for the accumulation of oligosaccharides. This carbohydrate analysis revealed the presence of large amounts (3--21) mumol/g fresh weight) of sialic acid in brain, liver, and kidney tissue as the major abnormality. Exhaustive characterization of the accumulating material by gel filtration, gas-liquid chromatography, thin-layer chromatography, and GLC-mass spectrometry positively identified the saccharide as free N-acetylneuraminic acid. Based on the accumulation of only free N-acetylneuraminic acid in the tissue of this patient, and normal activities of lysosomal enzymes involved in the catabolism of cellular glycoproteins, this storage disorder appears to result from a previously unreported defect in glycoconjugate metabolism.