title: Late onset GM2 gangliosidosis: an alpha-locus genetic compound with near normal hexosaminidase activity.
abstract: A non-Jewish child with late onset GM2 gangliosidosis is described. Tissues from the patient had near normal hexosaminidase A (hex A) activity using 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside (MU-glcNAc) as substrate, and deficient activity when assayed with the 6-sulphate derivative of MU-glcNAc (MU-glcNAcS) or GM2 in the presence of activator. We present evidence that this patient is a genetic compound for different alpha-subunit mutations. The father's tissues have hex A activity in the heterozygote range when assayed with MU-glcNAcS, but normal activity using MU-glcNAc; the mother's tissues have activities toward both substrates in the heterozygote range. These results emphasize the pitfalls of using only MU-glcNAc for the diagnosis of unusual variants of GM2 gangliosidosis.
authors.forename: J
authors.initials: J
authors.lastname: Charrow
authors.forename: K
authors.initials: K
authors.lastname: Inui
authors.forename: D A
authors.initials: DA
authors.lastname: Wenger
mesh_terms: D000117:Acetylglucosamine / Q000031:analogs & derivatives*; D000483:Alleles; D002675:Child, Preschool; D005260:Female; D005944:Glucosamine / Q000031:analogs & derivatives; D006579:Heterozygote; D054818:Hexosaminidase A; D006596:Hexosaminidases / Q000235:genetics*; D006801:Humans; D006923:Hymecromone / Q000031:analogs & derivatives; D009154:Mutation; D010375:Pedigree; D013379:Substrate Specificity; D013661:Tay-Sachs Disease / Q000201:enzymology* / Q000235:genetics; D001619:beta-N-Acetylhexosaminidases
chemical_list: C025158:4-methylumbelliferyl 2-acetamido-2-deoxy-beta-D-glucopyranoside; D006923:Hymecromone; C043647:4-methylumbelliferyl-6-sulfo-2-acetamido-2-deoxy-beta-glucopyranoside; D006596:Hexosaminidases; D054818:Hexosaminidase A; D001619:beta-N-Acetylhexosaminidases; D005944:Glucosamine; D000117:Acetylglucosamine