Delta thalassemia: a non-deletion defect

Hematological and gene mapping studies of two Southern Italian children doubly heterozygous for delta 0-thalassemia and delta 0 beta 0-thalassemia have been carried out. No HbA2 was detectable by electrophoresis of total hemoglobin in these patients. Restriction enzyme analysis of the globin gene cluster with delta, gamma, epsilon and RIH cloned probes showed all the expected normal bands, in addition to the abnormal fragments related to a previously described type of delta 0 beta 0-thalassemic deletion, demonstrating an apparently intact globin gene cluster on the thalassemic chromosome. The relevance of this finding to models for coordinated expression of non alpha globin genes is discussed.