Sialic acid storage disease with sialuria: clinical and biochemical features in the severe infantile type.

Two unrelated infants with a new disorder characterized biochemically by elevated levels of free sialic acid in urine, serum, and cell lysates have exhibited severe mental and physical impairments since the early weeks of life. Three other biochemically diagnosed cases and two possible cases from the earlier literature are reviewed to delineate this condition. Clinical features including sparse, white hair, coarse facies, hepatosplenomegaly, profound inactivity, diarrhea, and anemia permit early diagnosis of this neurovisceral storage disease. Osseous stippling may be present and clear vacuoles may be demonstrated in lymphocytes and cultured fibroblasts. The course is one of relentless deterioration with death in early childhood. Specific diagnosis depends on demonstration of elevated free sialic acid in urine and cell lysates.