A Japanese case of infantile sialic acid storage disease.

We report a 4-year-old Japanese girl with infantile sialic acid storage disease. She presented with failure to thrive, coarse facial features, hepatosplenomegaly, severe mental retardation and spastic quadriplegia. Electron microscopic examination of cultured skin fibroblasts revealed multiple vacuoles and inclusion material representing distended lysosomes, thus suggesting a lysosomal storage disorder. A high concentration of free sialic acid was present in the urine and cultured fibroblasts, but bound sialic acid was not increased. The activity of a variety of lysosomal enzymes was not diminished. The MRI findings included brain atrophy and a diffuse high signal in the cerebral white matter and low signal in the basal ganglia on T2-weighted images. To our knowledge, this is the first case of infantile sialic acid storage disease described in a non-Caucasian family.