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Hb A2 was determined in 50 subjects with erythrocyte G-6-PD deficiency who presented with hyperbilirubinemia in the neonatal period and in 100 non-hyperbilirubinemic G-6-PD deficient newborn infants, at the age of 12 months or more. Six subjects in the first group and 13 in the second were found to be carriers of the beta-thalassemia trait. Statistical analysis of the data did not show any significant difference between the two groups. It seems that the beta-thalassemia trait does not provide any protection against neonatal hyperbilirubinemia associated with G-6-PD deficiency.

Glucose-6-phosphate dehydrogenase (G6PD, D-glucose 6-phosphate: NADP oxidoreductase, E.C. 1.1.1.49) activity and the percentage of G6PD deficient erythrocytes was determined in 50 girls heterozygous for G6PD deficiency, 25 of whom had had hyperbilirubinaemia at birth and 25 who had normal bilirubin levels. The enzymatic activity was 2.32 +/- 0.87 I.U./g Hb in the first group and 3.31 +/- 0.92 I.U./g Hb in the second group. The percentage of G6PD deficient erythrocytes was 54.1 +/- 15.3 and 65.3 +/- 14.0, respectively. The level of enzymatic activity exceeded 4 I.U./g Hb and the percentage of G6PD deficient cells fell below 40% in only one of the subjects who had developed hyperbilirubinaemia. Levels of enzymatic activity below 4 I.U./g Hb, or percentages of G6PD deficient erythrocytes higher than 40% can therefore be considered to be associated with a high risk of developing neonatal hyperbilirubinaemia. In our opinion, these babies should receive prophylactic treatment with phenobarbital, as do G6PD deficient Mediterranean males.

We have investigated the association of neonatal jaundice (NNJ) and G6PD deficiency in consecutive births in a Northern Sardinian hospital. After excluding known causes for NNJ, and after correcting for the incidence of NNJ from unknown causes, we estimated that 20% of G6PD deficient male newborns develop NNJ resulting from their enzyme deficiency. By analyzing in detail 100 G6PD deficient babies we found no differences in birth weight or haemoglobin level between those without and those with NNJ, four of whom required exchange transfusion. We further showed by an accurate quantitative method that the residual G6PD enzyme activity was not significantly lower in G6PD deficient babies with NNJ compared to G6PD deficient babies without NNJ.

40 full-term newborn infants with erythrocyte glucose-6-phosphate dehydrogenase (G-6-PD) deficiency were used for a study concerning the effectiveness of agar per os in preventing severe hyperbilirubinemia. 20 randomly selected neonates were given agar (1 g/kg/day) orally in 4 daily doses from their 1st to their 5th day of life. 20 infants were not treated and served as controls. Three exchange transfusions were performed in the experimental as well as in the control group. According to these results, agar does not seem to be effective in preventing severe hyperbilirubinemia, which frequently occurs in newborn infants with erythrocyte G-6-PD deficiency.

Phototherapy was employed in treatment of newborn infants with erythrocyte G-6-PD deficiency whose serum bilirubin concentrations exceeded 10 mg/100 ml on the second or third day of life. Exchange transfusions were required for two of the 12 treated babies and for six of the 12 control infants. It is noteworthy that exposure to light did not affect the erythrocyte GSH content nor did it increase hemolysis.

53 newborn infants with both G-6-PD deficiency (29 male hemizygotes and 24 female heterozygotes) and alpha-thalassaemia, and 120 newborn infants with only the enzymatic defect (60 male hemizygotes and 60 female heterozygotes) were studied. 12 of those with both G-6-PD deficiency and alpha=thalassaemia, and 32 of those with only G-6-PD deficiency showed hyperbilirubinaemia. alpha-Thalassaemia does not seem to be implicated in the development of hyperbilirubinaemia in G-6-PD-deficient newborns.