Infantile type 2 sialidosis in a Pakistani family--a clinical and biochemical study.

Two siblings of consanguineous parents presented in infancy with failure to thrive, mild coarsening of facies, visceromegaly and corneal opacities. One showed reduced hepatic beta-galactosidase activity suggesting a GM1-gangliosidosis variant. Both patients developed progressive coarsening of facies, slow neurological deterioration, macular cherry-red spots and punctate cataracts over the first decade. Urine screening with thin layer chromatography revealed abnormal excretion of two slow-moving oligosaccharide bands and leukocyte and fibroblast neuraminidase activity was grossly reduced. The mother, phenotypically normal, showed levels of neuraminidase compatible with heterozygosity. These patients have primary neuraminidase deficiency. The clinical and biochemical variables are reviewed.