Molecular characterization of thalassemia intermedia associated with HPFH-6/beta-thalassemia and HPFH-6/Hb E in Thai patients.

We report the molecular and hematological characterizations of thalassemia caused by interactions of the hereditary persistence of fetal hemoglobin (HPFH)-6 with beta-thalassemia in 2 Thai patients and the HPFH-6 with Hb E in another Thai patient. Marked hypochromic microcytosis, characteristics of thalassemia intermedia, were obvious in the former 2 cases but the latter had much milder clinical phenotype with normal Hb and a slightly reduced mean corpuscular volume (MCV) value. Hb analysis revealed no Hb A but Hb A(2)F patterns in the compound HPFH-6/beta-thalassemia patients and the EF pattern in the HPFH-6/Hb E patient. The (G)gamma-globin chain predominated in all cases. Globin gene analyses demonstrated that all patients carried the 101-kb HPFH-6 deletion in trans to the beta-thalassemia genes with the IVS1#5 G-C mutation and the G insertion between codons 8/9 and the beta(E)-gene, respectively. Hematologic data of the patients were compared to those of the HPFH-6 heterozygotes found in their family members and different genotype-phenotype interactions of this HPFH determinant in these Thai patients are illustrated.