Hemoglobinopathy refers to a group of hereditary hemolytic anemias. These disorders are classified into two major categories: abnormalities in the quantity of globin chain synthesis (thalassemia) and structural abnormalities in hemoglobin (abnormal hemoglobinopathies). Hemoglobin consists of a heme group containing ferrous iron (Fe2+) and globin proteins. Each hemoglobin molecule contains two pairs of globin chains: one pair of α-like chains (α chain and ζ chain) and one pair of non-α chains (ε, β, γ, or δ chains). Each globin chain is linked to a heme group, forming a hemoglobin monomer. Human hemoglobin is composed of two pairs (four individual) hemoglobin monomers aggregated together.
In healthy individuals after birth, there are three types of hemoglobin:
- Hemoglobin A (HbA, α2β2), which constitutes over 95%.
- Hemoglobin A2 (HbA2, α2δ2), which accounts for 2%–3%.
- Fetal hemoglobin (HbF, α2γ2), which makes up about 1%.
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