Absence of Cis Delta Chain Synthesis in (δ β) Thalassemia (F-thalassemia)

Abstract

Abstract (δ β) thalassemia or F-thalassemia is characterized by a thalassemic blood picture, elevated hemoglobin F, and normal hemoglobin A2. A family with (δ β) thalassemia is reported in which the propositus was a mixed heterozygote for (δ β) thalassemia and hemoglobin B2. There was complete absence of hemoglobin A2, indicating that this (δ β) thalassemia mutation completely suppressed the cis delta gene. The remaining normal delta gene was capable of increasing delta chain synthesis sufficiently to bring the hemoglobin A2 to within normal range. These findings account for the absence of elevated hemoglobin A2 in this form of thalassemia and demonstrate that (δ β) thalassemia is an entity genetically distinct from A2 thalassemia. The possible genetic mechanisms of (δ β) thalassemia are discussed.