A new alpha-thalassemia-2 deletion resulting in microcytosis and hypochromia and in vitro chain imbalance in the heterozygote.

We have detected a novel alpha-thalassemia-2 with a large (18+ kb) deletion involving the alpha 1- and theta 1-globin genes and the 3' hypervariable region sequence. Unexpectedly, the heterozygote had a mild anemia with a marked microcytosis and hypochromia, and an in vitro alpha/beta chain synthesis ratio of 0.62-0.66. It is suggested that the deletion includes a sequence that is involved in the in cis regulation of the alpha 2-globin gene.