Molecular characterization of deletional forms of beta-thalassemia in Taiwan

beta-Thalassemia is one of the most common genetic diseases in Taiwan. The most common mutations of beta-globin are point mutations, and six mutations account for over 90% of cases. Less than 5% of the cases with beta-globin gene deletion result in beta-thalassemia minor. The mutational type of the deletion is not clear in Taiwanese. We used polymerase chain reaction (PCR)-based methods to detect the breakpoint junctions of different deletional types of beta-thalassemia. In total, six cases of clinically suspected deletional type of beta-thalassemia were studied. The results showed that there were three types of deletions in these cases: two cases each for hereditary persistent fetal hemoglobinemia (HPFH) of the Southeast Asian (SEA) type, HPFH of the Yunnanese type, and gamma(G)+(gamma(A)deltabeta)(0)deletions, respectively. The clinical features of these deletional mutations are milder than the beta(o) types of the point mutation. The patients with compound heterozygous mutations of the point mutation and the deletional mutation are always transfusion independent.