Thalassaemia

Thalassaemia is a group of diseases characterised by one or more defective globin genes, causing haemolytic anaemia. Like sickle cell anaemia it is more common in Africa and the Mediterranean, but also south-east Asia.

Pathophysiology

We distinguish alpha and beta thalassaemia, based on whether the alpha or beta globin genes are defective. Alpha globin chain production is controlled by two genes, so there are four alleles that can be defective. Beta globin chain production is controlled by only one gene so there are only two alleles that can be defective.

Clinical features

The clinical features of each type depend on how many alleles are defective. In alpha thalassaemia, one or more of the four genes for the alpha globin chain are deleted. In beta thalassaemia, one or both of the genes for the beta globin chain are defective.

Severity of the anaemia increases with increased number of affected genes, and ranges from asymptomatic to mild haemolytic anaemia to severe haemolytic anaemia. If all four alpha genes are deleted, the condition is incompatible with life (Hb Barts -> hydrops foetalis).

Diagnosis and evaluation

• Laboratory results
  • Corresponding to haemolytic microcytic anaemia
  • RDW normal or ↑
• Peripheral blood smear
  • Target cells
  • Teardrop cells
• Bone marrow biopsy
  • Reactive hyperplasia
• Haemoglobin electrophoresis – to confirm diagnosis
• DNA analysis (PCR) – to confirm diagnosis

Treatment

In mild thalassaemias, no treatment is necessary. In severe ones, lifelong regular blood transfusions are necessary. Treatment with iron chelators is necessary to prevent iron overload. Haematopoietic stem cell transplantation could be curative in severe cases.