Early onset of fetal hydrops associated with the α-thalassemia - -(THAI) deletion.

α-Thalassemia (α-thal) is common in southern China. Homozygosity for the - -(SEA) (Southeast Asian) α-globin gene deletion is the most common cause of the Hb Bart's (γ4) disease. Occasionally, other α(0)-thal deletions can also be found. In this study, we report a case with an atypical form of Hb Bart's disease. The fetus was a compound heterozygote for the - -(SEA) and - -(THAI) deletions and presented different clinical features from that of traditional Hb Bart's disease with the - -(SEA) deletion in the homozygous state. 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 finding may have potentially important implications for clinical decisions in a program using ultrasonography to identify signs of homozygous α(0)-thal.