Genetic diversity of the "Mediterranean" glucose-6-phosphate dehydrogenase deficiency phenotype.

Genetic diversity of the "Mediterranean" phenotype of G-6-PD (glucose-6-phosphate dehydrogenase) deficiency was revealed when detailed studies were performed on blood specimens from 79 Greek males with G-6-PD levels 0-10% of normal. Four different mutants were found to be responsible for the severely deficient phenotypes: two mutants. G-6-PD U-M (Union-Markham) and G-6-PD Orchomenos, were distinguishable by electrophoresis, while the other two. G-6-PD Athens-like and G-6-PD Mediterranean, were distinguishable on the basis of their kinetic characteristics. Of the kinetic tests applied, the most useful for differentiating the variants were those measuring utilization rates of the analogue substrates deamino-NADP, 2-deoxyglucose-6-phosphate, and galactose-6-phosphate. Among unrelated males with severe G-6-PD deficiency, the relative frequencies of the four variants were: G-6-PD U-M. 5%; G-6-PD Orchomenos, 7%; G-6-PD Athens-like, 16%; G-6-PD Mediterranean, 72%. Genetic, biochemical, and clinical implications of the findings are discussed.