Coinheritance of the different copy numbers of alpha-globin gene modifies severity of beta-thalassemia/Hb E disease.

beta-Thalassemia/Hb E patients show a range of clinical severities, from nearly asymptomatic to transfusion-dependent thalassemia major. This study investigated the clinical heterogeneity and hematologic parameters obtained in the large cohort of 925 Thai beta 0-thalassemia/Hb E patients. Coinheritance of alpha-thalassemia with beta 0-thalassemia/Hb E produces a milder clinical phenotype in contrast to an interaction of alpha-globin gene triplication in severe thalassemia. The mean steady-state Hb was also higher, whereas the mean corpuscular volume and the percentage of Hb F were markedly lower in the former group. This finding demonstrates that the genetic combination leading to the more/less degree of alpha- to non-alpha-globin chains imbalance is indeed the cause of the severe/mild thalassemia phenotype.