Type 3 (chronic) GM1 gangliosidosis presenting as infanto-choreo-athetotic dementia, without epilepsy, in three sisters.

Three sisters (ages 27, 24, and 17 years) presented with slowly progressing dystonic dementia and spastic tetraparesis with infantile onset. CSF, bone marrow, and conjunctival cells showed storage vacuoles. Biochemical analysis revealed increased urinary oligosaccharide excretion and decreased activity of acid beta-D-galactosidase and beta-D-fucosidase in serum, leukocytes, and cultured fibroblasts. The parents' enzyme values were in the heterozygous range. This is the only case in the literature of severe dementia associated with the clinical symptoms of type 3 GM1 gangliosidosis. The clinical heterogeneity of GM1 gangliosidosis and the significance of the combination of beta-D-galactosidase and beta-D-fucosidase defects in this syndrome are discussed.