Infantile Sialic Acid Storage Disease: A Rare Cause of Cytoplasmic Vacuolation in Pediatric Patients

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Abstract
We report a case of infantile sialic acid storage disease (ISSD) in a black infant presenting in utero with nonimmune hydrops, ascites, and anemia requiring intrauterine transfusion. Uponbirth, the patient had prominent edema, large anterior fontanelle, partial absence of the rectus abdominis, dubbing of the left foot, gingival hypertrophy, short first metatarsals, prominent scrotal raphe, right heart dilatation, and left ventricular dysfunction. Radiographs showed pulmonary hypoplasia and piphyseal stippling. He died of respiratory failure at day 2. Autopsy demonstrated capillary nemangiomata, remote cerebral hemorrhages, and central nervous system periventricular leukomalacia, as well as severe cardio -and hepatosplenomegaly. Multiple single membrane-limited vacuoles consistent with enlarged lysosomes were present in virtually all cell types examined, with striking involvement of liver, myocardium, and placenta. Vacuolar contents were not identifiable by electron microscopy. Demonstration of elevated free sialic acid in urine, amniotic fluid, and cultured fibroblasts confirmed the diagnosis of ISSD. Characteristics of sialic acid storage diseases and their diagnosis are reviewed. ISSD should be considered in infants with empty cytoplasmic vacuoles in multiple tissue types.