Characterization of Hb Bart’s Hydrops Fetalis Caused by – –SEAand a Large Novel α0-Thalassemia Deletion

Hb Bart’s hydrops fetalis is the most severe and generally fatal clinical phenotype of α-thalassemia (α-thal), which is due to the deletion of all four functional α-globin genes of hemoglobin (Hb), resulting in no α-globin chain production (– –/– –). Homozygosity for the – –SEA (Southeast Asian) α-globin gene deletion is the main cause of the Hb Bart’s hydrops fetalis in Asia, especially South China. Occasionally, other α0-thal deletions can also be found. In this study, we report a case with an atypical form of Hb Bart’s hydrops fetalis that was caused by – –SEA and a large novel α0-thal deletion (– –GX) (Guangxi). The fetus with Hb Bart’s in our study presented fetal hydrops features in early gestation which was different from that of traditional Hb Bart’s hydrops fetalis with a homozygous – –SEA deletion. The early onset of fetal hydrops is attributed to the decreased formation of embryonic Hb Portland (ζ2γ2), which is proposed as a candidate for reactivation in cases of severe α-thal. Our findings indicated that it was important to characterize new or rare mutations, and highlighted the significance of using ultrasonography to identify signs of Hb Bart’s hydrops fetalis.