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 ?-a thalassemia 1 (??aa/-) and the father has non-deletion a thalassemia [??aa/??(aa)(T)]. The complete deletion of the ?-a cluster on one chromosome was confirmed by quantitation of a and ? gene numbers, the normal a and ? gene patterns arising from the remaining normal chromosome, and the decreased a/ß globin chain ratio of 0.57. The non-deletion a thalassemia defect could only be identified by the imbalanced a/ß 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 a thalassemia defect is more severe than a thalassemia 2. The decreased ? 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 ? genes may be used for future prenatal diagnosis.