Hydrops fetalis due to an unusual form of Hb H disease

Abstract

The occurrence of Hb H hydrops fetalis is reported for the first time. The mother has ζ-α thalassemia 1 (ζζαα/--) and the father has non-deletion α thalassemia [ζζαα/ζζ(αα)(T)]. The complete deletion of the ζ-α cluster on one chromosome was confirmed by quantitation of α and ζ gene numbers, the normal α and ζ gene patterns arising from the remaining normal chromosome, and the decreased α/β globin chain ratio of 0.57. The non-deletion α thalassemia defect could only be identified by the imbalanced α/β globin chain ratio of 0.65 in the presence of normal gene numbers and patterns. The newborn was markedly anemic, unlike those with classical Hb H disease, because the non-deletion α thalassemia defect is more severe than α thalassemia 2. The decreased ζ genes during fetal life might have additional deleterious effects. In this family, the distinct BamHI restriction fragment length polymorphism in the hypervariable region of the ζ genes may be used for future prenatal diagnosis.