Atypical adult G_M1 gangliosidosis: Biochemical comparison with other forms of primary ß-galactosidase deficiency

We studied ß-galactosidase in skin fibroblasts from patients with different forms of ß-galactosidase deficiency: adult G_M1 gangliosidosis, type 1 GMl gangliosidosis, and Morquio B syndrome. Enzyme properties in the adult cases differed from the other disorders and also from normal controls. Genetic hybridization studies indicated that all three forms belong to the same complementation group. Therefore, the adult disorder must be due to a mutation of the structural gene for ß-galactosidase, which is allelic to the mutations in type 1 G_M1 gangliosidosis and Morquio B syndrome.