β-Thalassemia Associated with α-Thalassemia in Thailand

Abstract

In Thailand α-thalassemia (thal), β-thal, hemoglobin (Hb) E and Hb Constant Spring (Hb CS) are prevalent. The incidences are 20–30% for α-thal (3.5% for α-thal-1 and 16% for α-thal-2), 3–9% for β-thal, up to 54% for Hb E and nearly 8% for Hb CS (1). Different combinations of these genes result in a spectrum of thalassemia syndromes ranging in severity from asymptomatic to intrauterine death. From the known gene frequencies the numbers of thalassemic patients per generation (total population of 50 million) are as follows: Hb Bart's hydrops fetalis 20,000; homozygous β-thal 31,250; β-thallHb E disease 162,500; Hb H disease (two genotypes) 200,000, making a total of 413,750. In addition, individuals may carry more than two of the abnormal genes leading to complex thalassemia syndromes such as αβ-thal, AE-Bart's and EF-Bart's diseases.