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## Alpha Thalassemia - Has a wide range of clinical expression. - Predominant cause of alpha thalassemia is alpha globin chain gene deletion. - There are 4 alpha globin chain gene located on chromosome 11 - Absence of alpha chains will result in increase of gamma chains during fetal life and excess...

## Alpha Thalassemia - Has a wide range of clinical expression. - Predominant cause of alpha thalassemia is alpha globin chain gene deletion. - There are 4 alpha globin chain gene located on chromosome 11 - Absence of alpha chains will result in increase of gamma chains during fetal life and excess beta chains later in life, resulting in production of Bart's Hemoglobin (γ4) or Hemoglobin H (β4), which are stable molecules but functionally useless. - There are four clinical syndromes present in alpha thalassemia: - Silent carrier state (one gene deletion) - Alpha thalassemia trait (alpha thalassemia minor, two gene deletions) - Hemoglobin H disease (three gene deletions) - Bart's hydrops fetalis syndrome (four gene deletions) ### Classification of Alpha Thalassemia | No. of Genes Present | Genotype | Clinical Classification | |------------------------|-----------------------------|--------------------------| | 4 genes | *aa/aa* | Normal | | 3 genes | *aa/- a* | Silent carrier | | 2 genes | *- α/- α* or *aa/--* | α thalassemia trait | | 1 gene | *-α/--* | Hb HDs | | 0 genes | *--/--* | Hb Barts / Hydrops fetalis |