DELTA-PLUS THALASSEMIA IN SARDINIA ITALY

A new type of .delta.-thalassemia in which .delta.-globin chain synthesis is incompletely suppressed was defined. Homozygotes have unusually low HbA2 levels, and double heterozygosity for this .delta.-thalassemia gene and .beta.-thalassemia normalizes the HbA2 level. The .delta.-thalassemia occurs on a chromosome that is identifiable using polymorphic restriction endonuclease sites. This condition is called .delta.+-thalassemia, to distinguish it from the previously described .delta.0-thalassemia syndromes in which no .delta.-globulin chain synthesis occurs.