Genetics and Epigenetics Aspects of Thalassemia

Hemoglobin contains of heme, which binds iron and protoporphyrin, and globin, which consist of combination of α, β, δ, and γ chain. α-globin globin gene is located in 16p13.3 cytogenetically, and β-globin gene is in 11p15.4. Thalassemia is a blood disorder characterized in the lack or absence of one of globin chain. Thalassemia is classified as alpha thalassemia and beta thalassemia depending on which globin chain is reduced. Alpha thalassemia occurs when alpha globin chain in chromosome 16 is reduced or absence due to removal or deletion in the molecular level. Alpha thalassemia itself has several types including alpha thalassemia silence carrier, alpha thalassemia minor, haemoglobin H disease, and Hydrops fetalis. Alpha thalassemia silence carrier and alpha thalassemia minor is clinically asymptomatic. Hemoglobin H disease shows moderate to severe anemia symptom, while Hydrops fetalis is fatal. The reduced or absence of alpha globin chain causing the excess of beta globin chain. Beta thalassemia occur when beta globin chain synthesis is compromised mainly because of point mutation in chromosome 11. Beta thalassemia is divided into beta thalassemia minor, intermedia, and major. Beta thalassemia minor is clinically asymptomatic, while intermedia type shows symptoms between the minor and the major. Beta thalassemia major is the most severe among beta thalassemia, and regular blood transfusion may be needed of the anemia symptoms are increased. Besides genetic factors, epigenetic factors also play roles in causing thalassemia. Treatment of thalassemia is depended on its symptoms, such as blood transfusion and surgical treatment. Genetic therapy for thalassemia is still in development of therapy options.