Overview
- Alpha thalassaemia is an inherited condition affecting the alpha chains of haemoglobin, resulting in defective haemoglobin synthesis.
- Four alpha chain genes are inherited (two from each parent), and the type of alpha thalassaemia depends on how many of the four alpha chains are defective.
- Due to a lack of alpha chains, there is an increase in haemoglobin H (consisting of four beta chains).
- Alpha thalassaemia commonly occurs in people from South-East Asia, Mediterranean countries, Africa, the Middle East and India. The condition is very uncommon in caucasian populations.
Classification
Genotype Phenotype Silent Carrier α α / α - Mild to no anaemia Alpha Thalassaemia Minor / Trait α - / α - (cis)
α α / - - (trans)Hypochromic microcytic anaemia Haemoglobin H (HbH) Disease α - / - - Severe hypochromic microcytic anaemia
HbH inclusions (supravital staining)Hydrops Foetalis - - / - - Fatal in utero
Diagnosis
Test Findings in Alpha Thalassaemia
Full Blood Count & Film
- Microcytic hypochromic anaemia
- Anisocytosis: variation in red blood cell size
- Poikilocytosis - target cells, teardrop cells, elliptocytes, fragments
- HbH bodies (on supravital staining)HbH disease only
- Basophilic stippling
- Nucleated red blood cells
Other Tests
- High performance liquid chromatography / haemoglobin electropheresis - increased haemoglobin HNormal in thalassaemia trait - used for the diagnosis of HbH disease only
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