Hemolytic disease of the newborn caused by a new deletion of the entire beta-globin cluster.

We describe a new type of gamma delta beta-thalassemia in four generations of a family of Scotch-Irish descent. The proposita presented with hemolytic disease of the newborn, which was characterized by a microcytic anemia. Initial restriction endonuclease analysis of the DNA showed no grossly abnormal patterns, but studies of polymorphic restriction sites and gene dosage revealed an extensive deletion that removed all the beta- and beta-like globin genes from the affected chromosome. In situ hybridization of chromosome preparations with radioactive beta-globin gene probes showed that only one 11p homolog contained the beta-globin gene cluster in the affected family members.