Hemoglobin E disease

Hemoglobin E disease (Hb E disease) is a hemoglobin variant disorder caused by a structural mutation in the beta-globin gene (HBB), specifically a glutamic acid to lysine substitution at position 26 (Glu26Lys). It is one of the most common hemoglobin variants worldwide, particularly prevalent in Southeast Asian populations, including those of Thai, Cambodian, Laotian, and Vietnamese descent. Hemoglobin E disease can exist in the homozygous state (Hb EE), the heterozygous carrier state (Hb E trait), or in compound heterozygosity with other hemoglobin disorders such as beta-thalassemia (Hb E/beta-thalassemia). In the homozygous state (Hb EE), the condition is generally mild. Affected individuals typically present with microcytosis (small red blood cells) and mild hypochromia, but usually have only a mild anemia or may even be clinically asymptomatic. The red blood cells may show target cells on peripheral blood smear. Slight splenomegaly may occur in some individuals. The Hb E mutation also creates an alternative splice site in the beta-globin mRNA, resulting in reduced production of the variant beta-globin chain, which gives it a mild thalassemic character. Most individuals with homozygous Hb E disease lead normal lives without significant clinical complications. Treatment for homozygous Hb E disease is generally not required, as the anemia is mild and well-tolerated. Folic acid supplementation may be recommended. Genetic counseling is important, particularly for couples at risk of having children with the more severe compound heterozygous condition Hb E/beta-thalassemia, which can cause transfusion-dependent thalassemia. Diagnosis is confirmed through hemoglobin electrophoresis, high-performance liquid chromatography (HPLC), or molecular genetic testing of the HBB gene. Newborn screening programs in regions with high prevalence can identify affected individuals early.

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