A beta-thalassemia variant associated with unusually high hemoglobin A2 in an Iranian family.

Despite the vast heterogeneity of mutations, the levels of increased hemoglobin (Hb) A2 seen in individuals of different racial groups heterozygous for the different P-thalassemia mutations are remarkably uniform and rarely more than 6%. However, unusually high levels of Hb A2 have been observed in some P-thalassemia heterozygotes; in one group, it is associated with a partial or complete deletion of the P globin gene.' We describe here an Iranian family with a Po-thalassemia mutation caused by a 290-bp deletion that removes the 5' region of the p gene including the messenger RNA (mRNA) cap site and entire exon I. As seen in previous cases, individuals heterozygous for this deletion have a typical P-thalassemia trait phenotype but unusually high levels of