Thalessemia | Anatomy2Medicine
Thalassemia Types

Thalessemia

 

  • Thalassemias
      • characterized by deficient production of either α- or β-globin chains of hemoglobin.
      • Heme synthesis is unaffected. (MCQ)
    • β-Thalassemias
      • most common forms of thalassemia
      • caused by defects in the promoter sequence, in introns, or in coding regions of the β-globin gene. (MCQ)
      • β-Thalassemia major
  • also known as Mediterranean anemia or Cooley anemia.
        • It results from compound heterozygosity or homozygosity for thalassemic variants of the β-globin gene
        • aggregation of excess α- chains causes anemia
        • it is characterized clinically by:
          • Marked anemia resulting from:
            • Modest decrease in hemoglobin synthesis
            • Marked shortening of red cell life span due to aggregation of insoluble excess α-chains(MCQ)
            • Ineffective erythropoiesis(MCQ)
            • Relative folate deficiency
  • Marked splenomegaly(MCQ)
  • Distortion of skull, facial bones, and long bones because of erythroid marrow expansion(MCQ)
          • Thalassemic red cell morphology
            • marked microcytosis, hypochromia
            • target cells
            • extensive changes in size and shape
          • Increased hemoglobin F (α2γ2) throughout life (MCQ)
  • Generalized hemosiderosis due to chronic hemolysis, ineffective erythropoiesis, and repeated transfusions(MCQ)
      • β-Thalassemia minor
        • results from heterozygous inheritance of thalassemic variants of the β-globin gene.
        • Clinical manifestations include
          • minimal hypochromic microcytic anemia
          • increase in hemoglobin A2 (α2δ2), a normally occurring minor hemoglobin fraction. (MCQ)
  • This finding is useful in distinguishing β-thalassemia minor from iron deficiency anemia and the anemia of chronic disease.
  • Sickle cell thalassemia
      • results from coinheritance of hemoglobin S gene and a thalassemic variant of the β-globin gene (compound heterozygosity).
      • It is clinically similar to, but often less severe than, sickle cell anemia. (MCQ)
  • α-Thalassemias
    • most common forms of thalassemia in Southeast Asia.  (MCQ)
    • They are caused by deletions of one or more of the four α-globin genes
    • In normal persons, there is duplication of the α-globin gene, with a pair of identical α-globin genes on each member of the chromosome 16 pair. (MCQ)
    • Deletion of one or more of the four α-globin genes
      • with one gene deletion;
        • No clinical abnormalities
      • with two or three deletions
        • mild-to-moderate thalassemic state
      • with four deletions
        • intrauterine death
        • hemoglobin Barts (γ4) in fetal life (MCQ)
        • hemoglobin H (β4) in adult life (MCQ)