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
Next Page
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------