Fifty-one girls, aged 2–10 yr, who had had hemolytic crises requiring hospitalization after the ingestion of fava beans, were randomly selected and examined for G6PD activity and percent of G6PD deficient red cells. The parents as well as 35 GdMediterranean heterozygous females who had never had significant hemolytic crises were also examined. GdMediterranean heterozygous females showed a G6PD activity of 2.58 ± 0.69 IU/gHb. The percent of deficient red cells was 60.09 ± 10.1 ranging from 45–85%. A clear correlation between the G6PD activity and percent of enzyme-devoid red cell was found. The distribution of the subjects examined according to the percent of G6PD deficient red cells is significantly shifted in favor of those whose percent of G6PD-red cells is higher than 50%. This is more conspicuous in subjects already hospitalized for a hemolytic crisis as compared to subjects who had never had hemolytic crises. In the group of girls hospitalized for a severe hemolytic crisis after ingestion of fava beans, we observed 39% homozygotes and 61% heterozygotes. Among the heterozygotes, only three subjects developed severe crises as to require transfusion. On the basis of the number of heterozygotes hospitalized for a hemolytic crisis and on the number of crises-free heterozygotes out of the population as a whole, we drew a probability curve showing the risk for G6PD deficient heterozygous females to develop hemolytic crises during childhood. This risk does not exceed an average of 1.3%.Speculation
The findings that G6PD deficient heterozygous females have a low probability of developing a significant hemolytic crisis during childhood and that such crisis is always moderately severe has a practical utility in genetic counselling and in the prescription of drugs that may be potentially harmful to G6PD deficient female heterozygotes.