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Objective: The aim of this study was to characterize unknown β-globin gene mutations in individuals who attended Songklanagarind Hospital for thalassemia screening and genetic counseling.Material and Methods: β-thalassemia mutations in individuals with hemoglobin (Hb) A2 levels >3.5% originating from various provinces in southern Thailand were characterized by reverse dot blot hybridization (RDB) and multiplex gappolymerase chain reaction using a panel of 30 allele-specific probes for point mutations and 6 sets of specific primers for large deletions. Mutations which could not be identified by these two methods were further analyzed by direct deoxyribonucleic acid (DNA) sequencing.Results: Nineteen subjects found to have uncharacterized β-globin gene mutations were analyzed by direct DNA sequencing. Nine different rare mutations were identified, four of which have not been to date described in Thailand: -30 (T>C), codon 5 (-CT), Hb Monroe (codon 30, G>C) and Hb Hammersmith (codon 42, T>C). An Hb Hammersmith mutation detected in one subject appeared to be a spontaneous mutation, unrelated to family history. The other five mutations have been reported previously within Thailand, but here they were identified in the southern part of Thailand for the first time: -31 (A>G), codon 15 (-T), codon 35 (C>A), codon 95 (+A) and Hb Dhonburi (codon 126, T>G). The presence of the mutations was confirmed by RDB.Conclusion: In addition to the already reported β-globin gene mutations, 9 other different types of mutations were identified. This information should be useful for planning genetic counseling and prenatal diagnosis programs for prevention and control of thalassemia diseases.

β-thalassemia (β-thal) (3.5 kb deletion or NC_000011.10:g.5224302-5227791del3490bp) is a common mutation in southern Thailand. This study aimed to determine genetic diversity in subjects with β-thal (3.5 kb deletion) alleles and to ascertain the origin of this mutation using haplotype and phylogenetic analysis. The study was carried out on members of the southern Thai population, including 45 normal individuals, 116 heterozygous β-thal (3.5 kb deletion) and one homozygous β-thal (3.5 kb deletion). The 5′-haplotype in β-globin gene cluster was examined using newly developed reverse dot blot hybridization (RDB) and compared with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results showed 100% concordance between the haplotype patterns of these two methods. From a total of 324 chromosomes, nine haplotypes were segregated. Haplotype H2 (+ ----) was the predominant haplotype observed in all 118 β-thal (3.5 kb deletion) chromosomes, which revealed a single origin. The phylogenetic tree demonstrated that β-thal (3.5 kb deletion) has an older genetic defect in this region. Moreover, the developed RDB is simple, less time-consuming, inexpensive, and does not restriction enzyme digestion.