Homozygous HbE is common in Southeast Asia and presents with very mild anemia, seldom requiring transfusion. Over 30 million people in the world are HbE carriers, making this abnormal hemoglobin almost as common as HbS. HbE is uncommon in North America and in Europe, but with changing immigration patterns, HbE and related diseases cannot be ignored. Peripheral blood smear findings of target cells, microspherocytes, red cell hypochromia, red blood cell fragments, and nucleated red blood cells may be noted. Evidence from hemoglobin electrophoresis is required to establish a diagnosis.
Clinically, a very important and severe disease is HbE/beta thalassemia in which there is hemolysis requiring repeated transfusions. Severe anemia, low MCV, and elevated RBC are characteristic of HbE/beta thalassemia.