Overview
Beta thalassaemia is an inherited defect in beta globin chains of haemoglobin, resulting in defective haemoglobin synthesis.
Beta thalassaemia is common in people from Mediterranean countries, South East Asia and India. It is rarely seen in those of caucasian descent.
Classification
| Genotype | Phenotype | |
| Beta Thalassaemia Minor / Trait | β / βâ° β / β⁺ | Mild or no anaemia with marked microcytosis |
| Beta Thalassaemia Intermedia | β⁺ / β⁺ β⁺ / βâ° | Moderate microcytic hypochromic anaemia |
| Beta Thalassaemia Major | βâ° / βâ° | Severe microcytic hypochromic anaemia Bone marrow expansion Iron overload |
- β - normal beta chains
- β⁺ - reduced production of beta chains
- βâ° - no production of beta chains
Pathogenesis
Due to the lack of beta chains, there is an increase in haemoglobin A₂ (consisting of two alpha and two delta chains) and haemoglobin F (foetal haemoglobin, consisting of two delta and two gamma chains).
An excess of alpha chains, combined with ineffective haemoglobin production, lead to ineffective red cell production and shorted red cell lifespan. The resulting anaemia stimulates erythropoietin release and further red cell production, eventually producing bone marrow expansion and iron overload.
Manifestations
Beta thalassaemia minor / trait tends to be asymptomatic, while beta thalassaemia intermedia and major may present with significant signs and symptoms.
Clinical Features of Beta Thalassaemia
- Symptoms of anaemia - fatigue, lethargy, lightheadedness, shortness of breath, chest pain, headache
- Jaundice: yellow discolouration of the skin
- Hepatomegaly: enlarged liver
- Splenomegaly: enlarged spleen
Beta Thalassaemia Major
- Iron overload - hypogonadotrophic hypogonadism, hypothyroidism, hypoparathyroidism, diabetes mellitus, liver cirrhosis, heart failure
- Bone marrow expansion - bony deformities, osteoporosis, muscle wasting
Diagnosis
Test Findings in Beta Thalassaemia
Full Blood Count & Film
- Microcytic hypochromic anaemia
- Poikilocytosis - target cells, teardrop cells, elliptocytes, fragments
- Basophilic stippling
- Nucleated red cells
Other Tests
- High performance liquid chromatography / haemoglobin electrophoresis - increased haemoglobin A₂ and haemoglobin F
- Iron studies - elevated ferritin, elevated transferrin saturation (beta thalassaemia major)
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