In the following type of hemoglobinopathy due to a defect in Globin chain as shown in the image,which type of hemoglobin accumulates?
A. Hb A2
B. Hb F
C. Hb H
D. Hb A2 and Hb F
Ans:D.Hb A2 and Hb F
Beta thallasemia is shown in the image.
- In these disorders, synthesis of β-globin chains is decreased or absent, typically as a result of point mutations ,however, α-globin chain synthesis is normal.
- α-Globin chains cannot form stable tetramers and, therefore, precipitate, causing the premature death of cells initially destined to become mature RBCs.
- Increase in α2γ2 (Hb F) and α2δ2 (Hb A2) also occurs.
- There are only two copies of the β-globin gene in each cell (one on each chromosome 11).
- Therefore, individuals with β-globin gene defects have either β-thal assemia trait (β-thalassemia minor) if they have only one defective β-globin gene, or β-thalassemia major (Cooley anemia) if both genes are defective .
- Because the β-globin gene is not expressed until late in fetal gestation, the physical manifestations of β-thalassemias appear only several months after birth.
- Those individuals with β-thalassemia minor make some β chains, and usually do not require specific treatment.
- However, those infants born with β-thal assemia major are seemingly healthy at birth, but become severely anemic, usually during the first or second year of life due to ineffective erythropoiesis.
- Skeletal changes as a result of extramedullary hematopoiesis also are seen.
- These patients require regular transfusions of blood.Although this treatment is lifesaving, the cumulative effect of the transfusions is iron overload (a syndrome known as hemosiderosis).
- Use of iron chelation therapy has improved morbidity and mortality.
- The increasing use of bone marrow replacement therapy has been a boon to these patients.