Characterization of Hb Bart's Hydrops Fetalis Caused by - - SEA and a Large Novel α 0 -Thalassemia Deletion.

Hb Bart's hydrops fetalis is the most severe and generally fatal clinical phenotype of -thalassemia (-thal), which is due to the deletion of all four functional -globin genes of hemoglobin (Hb), resulting in no -globin chain production (--/--). Homozygosity for the --(SEA) (Southeast Asian) -globin gene deletion is the main cause of the Hb Bart's hydrops fetalis in Asia, especially South China. Occasionally, other (0)-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 (0)-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 (22), which is proposed as a candidate for reactivation in cases of severe -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.