Characterization of Hb Bart's Hydrops Fetalis Caused by - -SEA and 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.