Prenatal diagnosis of glycogen storage disease type Ia by restriction enzyme digestion.

Glycogen storage disease type Ia (GSD Ia) is an autosomal recessive condition, caused by a deficiency of hepatic glucose-6-phosphatase (G6Pase) activity. In a consanguineous family originating from northern Africa whose first daughter was affected with GSD Ia, we were able to identify the disease-causing mutation, a cytosine to thymine substitution at nucleotide 326 in exon 2 of the G6Pase gene (R83C). This mutation causes the disappearance of an HgaI site, and is thus easily detectable by restriction enzyme digestion. Both parents were heterozygous for this mutation. During the third pregnancy, fetal genomic DNA was extracted from a chorionic villus biopsy sampled at the 24th week of gestation. Exons 2 of the G6Pase gene were amplified by the polymerase chain reaction followed by HgaI digestion. Fetal DNA analysis indicated that the fetus had received both normal G6Pase alleles. This result was confirmed after birth. DNA analysis is the only reliable method for prenatal diagnosis of GSD Ia.