GM2D gangliosidosis B1 variant in a boy of German/Hungarian descent.

After the introduction of 4-methylumbelliferyl-2-acetamido-2-deoxy-βA-D-glucopyranoside (4MUG) and its sulfated form (4MUGS) in the pre- and postnatal diagnosis and carrier identification of gangliosidosis genotypes, infrequent forms of the GM 2 gangliosidosis Type B (Tay-Sachs disease) have been observed which show normal activity of Hexosaminidase A (Hex A) isoenzyme with the substrate 4MUG but absent or deficient activity against the sulfated form 4MUGS. Here we report the observation of a German/Hungarian boy aged 12 when he died with a prolonged course of a neurodegenerative disorder, later biochemically identified as a G M2 gangliosidosis B 1 -variant which is characterized by a deficient Hex A activity only against 4MUGS