Homozygous Hb E disease (a hemoglobinopathy—see Sidebar 1: Anemias Caused by Hemolysis: Hemoglobinopathies) causes a mild hemolytic anemia, usually without splenomegaly.

Hb E is the 3rd most prevalent Hb worldwide (after Hb A and Hb S), primarily in black and Southeast Asian (> 15% incidence of homozygous disease) populations, although rarely in Chinese populations. Heterozygotes (Hb AE) are asymptomatic. Patients heterozygous for Hb E and β-thalassemia have a hemolytic disease more severe than S-thalassemia or homozygous Hb E disease and usually have splenomegaly.

In heterozygotes (Hb AE), routine laboratory test results of peripheral blood are normal. In homozygotes, a mild microcytic anemia with prominent target cells exists. Diagnosis of Hb E disorders is by Hb electrophoresis. Treatment in homozygous patients with severe disease usually involves chronic transfusions.

Last full review/revision February 2009 by Alan E. Lichtin, MD