Hemoglobin Q-Thailand related disorders: Origin, molecular, hematological and diagnostic aspects

We describe the molecular and hematological profiles of thalassemia syndromes caused by interactions of hemoglobin (Hb) Q-Thailand [alpha 74(EF3) Asp-His] and various hemoglobinopathies found in 52 unrelated adult Thai subjects. Ten genotypes including several previously undescribed conditions were observed, which were classified into 4 groups. Group I included 26 Hb Q-Thailand heterozygotes and a homozygotous subject. Group II included subjects with Hb Q-Thailand and other alpha-thalassemia alleles in trans including 1 compound Hb Q-Thailand/alpha(+)-thalassemia (-alpha(3.7)), 2 Hb Q-Thailand/Hb Constant Spring disease and 6 Hb H/Q-Thailand disease. The average levels of Hb Q-Thailand were found to be 29.8%, 82.3%, 34.7%, 49.2-49.3% and 79.4%, respectively. Both Hbs Bart's and H were observed in addition to Hb Q-Thailand in all 6 cases with Hb Q-H disease but not in a homozygous Hb Q-Thailand. Group III included 7 double heterozygotes for Hb Q-Thailand/Hb E, 3 Hb Q-Thailand/Hb E/alpha(+)-thalassemia (-alpha(3.7)), 3 heterozygous Hb Q-Thailand/homozygous Hb E and 1 triple heterozygote for Hb Q-Thailand/Hb Constant Spring/Hb E. In this group, Hbs E (alpha(A)(2)beta(E)(2)), Q-Thailand (alpha(QT)(2)beta(A)(2)) and QE (alpha(QT)(2)beta(E)(2)) were observed on both HPLC and capillary electrophoresis. The Hb QE, rather than Hb Q-Thailand, was detected in all 3 cases with heterozygous Hb Q-Thailand and homozygous Hb E. The remaining two cases in group 4 were double heterozygotes for Hb Q-Thailand and beta(0)-thalassemia in which Hb Q-Thailand, elevated Hb A(2) (alpha(A)(2)delta(2)), and Hb QA(2) (alpha(QT)(2)delta(2)) were detected. DNA analysis identified the Hb Q-Thailand mutation (alpha 74: GAC-CAC) and the linked (-alpha(4.2)) in all cases. Analysis of alpha-globin gene haplotype provided the first evidence of a single origin of this Hb variant in Thai population. (C) 2010 Elsevier Inc. All rights reserved.