Molecular characterization of Hb H disease in southern Thailand

Genotypes of 260 individuals with hemoglobin H (Hb H) disease originating from various provinces in southern Thailand were characterized by multiplex PCR (M-PCR) and reverse dot blot hybridization (RDB). M-PCR was used to amplify target fragments and then hybridized with allele-specific oligonucleotide (ASO) probes which were bound on a nylon membrane. A total of eight -thalassemia (-thal) mutations, which produced eight Hb H disease genotypes ((0)-thal/(+)-thal), were detected. The most common form of (0)-thal was -SEA with a frequency of 99.23%. The other form (0.77%) of (0)-thal mutation was a THAI deletion (-THAI). The deletional (+)-thal mutations comprised 3.7kb (-(3.7)) and 4.2kb (-(4.2)) deletions which were found in 172 (66.15%) and 5 (1.92%) alleles, respectively. The incidence of non-deletional (+)-thal in decreasing order was Hb Constant Spring (Hb CS, (CS)) 28.85%, Hb Quong Sze (Hb QS, (QS)) 1.54%, and Hb Pakse (Hb PS, (PS)) 0.77%. The genotype characterization of Hb H disease and the development of the RDB technic for detection of -thal mutations presented in this study enable the prenatal diagnosis of Hb Bart's hydrops fetalis syndrome.