A 3-year-old boy developed progressive neurological deterioration in his third year, characterized by dementia, ataxia, myoclonic jerks, and bilateral macular cherry-red spots. Hexosaminidase A (HEX A) was partially decreased in the patient's serum, leukocytes, and cultured skin fibroblasts. Hexosaminidase was studied in serum and leukocytes from family members. Four members of the paternal branch appeared to be carriers of classical infantile Tay-Sachs allele, HEXα 2, probably receiving the gene from one great-grandparent of Ashkenazi origin. In the maternal branch, no one was a carrier of classical infantile Tay-Sachs disease, but five individuals were carriers of a milder α-locus defect. The patient, therefore, was a genetic compound of two different α-locus hexosaminidase mutations. At least 21 families with late-infantile or juvenile GM 2 gangliosidosis have been reported, 18 of them with α-locus mutations, and three with β-locus mutations. Genetic compounds of hexosaminidase have been reported in at least seven families, five with α-locus mutations and two with β-locus mutations. The compound had the phenotype of infantile Tay-Sachs disease in one family, infantile Sandhoff disease in another, and the normal phenotype in the rest. This is the first example, to the authors' knowledge, of a genetic compound with the juvenile GM 2 gangliosidosis phenotype. This finding has implications for the diagnosis of such patients, for prenatal diagnosis, and for Tay-Sachs screening programs. In addition, it emphasizes the importance of doing careful family studies in such patients.
|Original language||English (US)|
|Number of pages||11|
|Journal||American Journal of Human Genetics|
|State||Published - Oct 10 1980|
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