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Table 2 Alpha Thalassaemia Syndrome

From: Non-deletional alpha thalassaemia: a review

Normal α-globin genes available Significant phenotype Genotype Clinical findings Potential risks to the foetus
4 Normal αα/αα Clinically healthy None
3 α-thalassaemia-silent traits αα/−α –α/αα, αTα/αα, ααT/αα or αα/ααT Normal Hb, low MCV but no clinical manifestation HbH disease
2 α-thalassaemia carrier traits −−/αα, −α/−α,
T/αα, αTα/−α, αTα/αTα or αTαT/αα
Normally characterised by decreased Hb and MCV levels but no clinical manifestation HbH disease, Hb Bart’s hydrops foetalis
1 HbH disease -α/−−, ααT/−−, αTα/−−, αTαT/−α or ααT/−αT Moderate to severe anaemia, low Hb and MCV HbH disease, Hb Bart’s Hydrops Foetalis
0 Hb Bart’s hydrops foetalis −−/−−, −αT/−− or αTαT/−−, −αT/−αT or αTαT/−αT Very severe anaemia and hypoxia characterised by intra-uterine death. Hydrops foetalis is associated with profound anaemia, low Hb, MCV, MCH, and jaundice. Others include high white blood cells count, increased bilirubin, normal platelet and reticulocyte counts, and hepatosplenomegaly. Not compatible with life
  1. αT: Non-deletional mutation.