Molecular characterization of severe α-Thalassemias causing hydrops fetalis in Taiwan

α-Thalassemia hydrops fetalis is a common disorder in Taiwan. The condition causes perinatal death and many maternal obstetrical complications. In order to determine the molecular defects of this condition in Chinese, 87 unrelated families with this disorder were collected in the past 4 years. The molecular defects were studied by Southern blotting and DNA hybridization with φζ1-globin gene and LO (a 0.4 kb BamHI/EcoRI fragment in the 5′ flanking region of the ζ2-globin gene) probes. Eighty-one (93.1%) fetuses had homozygous Southeast Asian deletion (– –^SEA/– –^SEA). Five (5.7%) fetuses were compound heterozygotes for the Southeast Asian deletion and Thailand deletion (– –^SEA/– –^THAI). The remaining fetus was a compound heterozygote for the Southeast Asian deletion and an uncharacterized nondeletional defect (– –^SEA/(αα)Th). The molecular defects of α-thalassemia hydrops fetalis in Chinese are heterogeneous. This fact has important implications for genetic counseling and prenatal diagnosis.