Thalassaemia

The thalassaemias are a group of recessively autosomal inherited conditions characterised by decreased or absence of synthesis of one of the two polypeptide chains (α or β) that form the normal adult human haemoglobin molecule (1), resulting in alpha and beta thalassaemia respectively (1).

• alpha thalassaemia major is incompatible with life, beta thalassaemia major results in severe anaemia (2)

Inheritance of an affected gene from both parents results in a disorder and inheritance of only one affected gene results in a healthy carrier, sometimes called a trait. (3) There are other less serious thalassaemia disorders which can be detected by the screening programme

Classification of the disease is according to the clinical severity (phenotype) or type of mutation (genotype) (1).

Notes:

• Thalassaemias are the commonest genetic disorders in the world - approximately 5% of the global population carry a defective alpha-thalassaemia gene (4) and approximately 1.5% of the global population are heterozygous (carriers) for beta-thalassaemias (5)
• They occur in a very high frequency in a tropical belt extending from Africa, throughout the Mediterranean region, the Middle East, the Indian subcontinent, and throughout South West Asia. They occur sporadically in every population.
• It is possible that the heterozygote state provides protection against falciparum malaria, thus explaining its high carrier rate in certain populations

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• advice from the UK National Screening Committee on antenatal screening for thalassaemia....click here

Reference:

1. Peters  M, et al. Diagnosis and management of thalassaemia. BMJ 2012; 344,
2. Standards for the Clinical Care of Children and Adults with Thalassaemia in the UK, United Kingdom Thalassaemia Society 2008
3. NHS Screening programs, Sickle Cell and Thalassaemia Handbook for Laboratories, Octorber 2012
4. Thalassaemia International Federation. Guidelines for the management of alpha-thalassaemia. 2023.
5. De Sanctis V et al. β-Thalassemia Distribution in the Old World: an Ancient Disease Seen from a Historical Standpoint. Mediterr J Hematol Infect Dis. 2017;9(1):e2017018.