The genetics of α thalassemia in Yemenite and Iraqi Jews

Yemenite and Iraqi Jewish infants with Hb Barts at birth occurring in bimodal concentration peaks of 2% and 5-6%, were studied at the age of 1 to 6 yr by measuring synthetic activity of the globin chains (a/B ratio). All these subjects had impaired α chain synthesis, when they were otherwise hematologically normal, confirming that the presence of Hb Barts at birth is a reliable marker of α thalassemia. However, no bimodal peaks of decreased d/β ratios were observed. An attempt to arbitrarily separate α chain defects into 'mild' and 'strong' varieties according to degree of impaired α chain synthesis, did not correlate with the previous genetic concept of two types α thalassemic genes, when α/β ratios were determined in family studies, including Hb H families. The authors state that in this ethnic sampling, the observations favor inheritance of α thalassemia through a single mutant gene with variable expressivity. Hb H disease probably represents the homozygous state for this mutant gene.