Epidemiology

Mutations in the beta-globin gene cluster occur at high frequencies (>1%) in regions including the Mediterranean, Middle East, northern Africa, India, and almost all of Southeast Asia.[3]

These mutations have arisen spontaneously, and it has been proposed that the carrier state for this disorder and others such as sickle cell disease may confer a survival advantage in areas where malaria is endemic.[4]Plasmodium falciparum parasitaemia is reduced in vitro in beta-thalassaemia.[5] The higher concentration of fetal haemoglobin (Hb F) found in the red cells of people with haemoglobinopathies inhibits the development of the malarial parasite, but the mechanism of this effect is not well understood.[6][7]

Although the prevalence of these mutations is lower in the populations of northern Europe and North America, widespread immigration has led to worldwide distribution.[8] Approximately 1.5% of the global population are heterozygous (carriers) for beta-thalassaemias.[9]

Compound heterozygosity of beta-thalassaemia with haemoglobin E mutations may have a phenotype similar to beta-thalassaemia major or intermedia. The gene frequency for the haemoglobin E mutation is high in Thailand, Laos, Cambodia, and parts of southern China.[10]

It is estimated that over 90% of children born with significant beta-thalassaemia syndromes are from Asia, India, and the Middle East, and a large number involve haemoglobin E mutations.[11] In the developed world, newborn screening ensures early diagnosis and referral to the appropriate haematology service for management.

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