Prenatal Diagnosis of Glucose-6-Phosphate Dehydrogenase Deficiency
Ernest Beutler a
Wanda Kuhl a
Michelle Fox b
Khalil Tabsh b
Barbara F. Crandall b
a Department of Molecular and Experimental Medicine, Scripps Clinic and Research Foundation, La Jolla, Calif.;
b UCLA School of Medicine, UCLA Medical Center, Los Angeles, Calif., USA
Prior to the development of the DNA-based technology reliable prenatal diagnosis of G6PD deficiency was not possible. We show that, using PCR amplification and restriction endonuclease digestion, prenatal diagnosis is possible. We have now been able to determine that the male fetus of a mother heterozygous for G6PD Mediterranean had inherited the maternal X chromosome with the normal G6PD gene.
Severe neonatal jaundice due to G6PD deficiency is common in some populations [1-3] and may cause kernicterus . Until recently, however, prenatal diagnosis of G6PD deficiency has not been practical. The quantitative expression of the defect in tissues other than red cells is relatively mild  and it would have been necessary to depend upon kinetic or electrophoretic differences detected in studies of small amounts of enzyme to establish a diagnosis. With the development of DNA technology, it has become possible to diagnose G6PD mutants prenatally. We now report what is, to our knowledge, the first case in which the G6PD genotype has been determined before birth.
A 33-year-old gravida 1, para 0 woman of Syrian Jewish descent was seen in the 18th week of pregnancy for genetic counseling because of a low maternal serum alpha -fetoprotein level on a routine screening test. The husband was of Sephardic Jewish extraction. The patient gave a history of G6PD deficiency requiring blood transfusion following the ingestion of fava beans as a child. She expressed considerable anxiety about the G6PD status of the pregnancy.
The G6PD activity of the red cells of the patient was 5.44 IU/g Hb (NV= 7.9-16.3) . DNA was extracted from her leukocytes, the polymerase chain reaction was performed to amplify the portion of exon 6 which contains the C --> T mutation at nucleotide 563 characteristic of G6PD Mediterranean [7, 8], and the amplified DNA was digested with Mbo II as previously described . As shown in figure l, approximately half of the 127 base pair band of the patient digested into bands sized 72 and 55 base pairs.
Amniocentesis was performed to rule out Down syndrome and other chromosomal abnormalities. Karyotypic analysis showed the fetus to be male. Amniocytes were cultured and DNA extracted from the cells was examined for the mutation at nucleotide 563. As shown in figure 1, the DNA from the amniotic cells was not cleaved. In addition, we examined the polymorphic site at nucleotide 1311 of the G6PD coding region . This site is in almost complete linkage disequilibrium with G6PD Mediterranean in Middle Eastern populations, with the mutant T being present at nt 1311 whenever the 563T mutation exists [9, 10]. The mother was found to be heterozygous (C/T) at nt 1311. Since one can assume that the T at nt 1311 was on the same X chromosome as the T at nucleotide 563 the C at nt 1311 must have been on the normal X chromosome. Indeed, the DNA from the amniotic fluid cells had a C at nucleotide 1311.
Thus, we were able to show that the newborn was not G6PD deficient. Accordingly, there was no need for special concern about the development of neonatal jaundice. Moreover, it was possible to reassure the mother, who had herself experienced a life-threatening complication of G6PD deficiency, that her newborn would he free of this abnormality.
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