Abstract
Hematological phenotypes and molecular defects were compared in 11 examples of heterozygous (δβ)° thalassemia. Despite differences in ethnic origins all cases had the gene deletion that is found in (δβ)deg; thalassemia of the Southern Italian type. HbF levels in these patients ranged from 3.6–14.6% with a mean ± 1 SD of 8.9 ± 3.1%. Variability in HbF output would suggest that additional factor(s) apart from deletions within the β globin complex are involved in regulation of γ gene expression. One individual, a compound-heterozygote for (δ/β)° thalassemia and HbS, presented with a sickling disorder. Reduced HbF production in family members who are heterozygotes for (δ/β)° thalassemia may explain the clinical picture in this instance.