What is alpha thalassemia?

By William Aird

Occurs when there is a reduction in the synthesis of the α-globin chains of adult hemoglobin (HbA, α2β2) relative to beta-globin synthesis. Underproduction of α globin chains gives rise to excess β-like globin chains which form γ4 tetramers, called Hb Bart’s (in fetal life) and β4 tetramers, called HbH (in adult life).

  • α thalassemia trait:
    • Mutations affecting the α globin genes on one chromosome
    • Associated with minimal anaemia
  • Compound heterozygotes and some homozygotes for α thalassemia (HbH disease):
    • Moderately severe anemia
    • Presence of HbH in the peripheral blood
  • Hb Bart’s hydrops fetalis syndrome:
    • Little or no α globin chains have a very severe form of anaemia
    • May cause death in the neonatal period if left untreated
Genetics in Medicine • Volume 13, Number 2, February 2011

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