Patients with this rare disorder have developmental delay, hepatosplenomegaly and coarse facies. There is massive urinary excretion of sialic acid and also increased cellular content. However, the sialic acid in the cells is concentrated in the cytosolic fraction rather than in the lysosomes as in Salla disease and infantile N-acetylneuraminic acid storage disease. The defect is in feedback inhibition of the rate-limiting step in synthesis of sialic acid, viz impairment of feedback inhibition of UDP-N-acetylglucosamine-2-epimerase by CMP-N-acetylneuraminic acid.
METABOLITE TEST: N-acetylneuraminic acid is measured to diagnose this disorder.