The hemoglobin E thalassemias

Abstract

Hemoglobin E (HbE) is an extremely common structural hemoglobin variant that occurs at high frequencies throughout many Asian countries. It is a β-hemoglobin variant, which is produced at a slightly reduced rate and hence has the phenotype of a mild form of β thalassemia. Its interactions with different forms of α thalassemia result in a wide variety of clinical disorders, whereas its coinheritance with β thalassemia, a condition called hemoglobin E β thalassemia, is by far the most common severe form of β thalassemia in Asia and, globally, comprises approximately 50% of the clinically severe β-thalassemia disorders.

Figure 1.

The peripheral blood film in hemoglobin E trait showing normal red cell morphology.

Figure 2.

The peripheral blood film in the homozygous state for hemoglobin E showing large numbers of target cells.

Figure 3.

The peripheral blood film in hemoglobin E β thalassemia after splenectomy showing numerous nucleated red cells and a high platelet count.

Figure 4.

Pulmonary vascular occlusion in hemoglobin E β thalassemia after splenectomy.