Association of Hb Q-Thailand with homozygous Hb E and heterozygous Hb Constant Spring in pregnancy
Eur J Haematol 2005: 74: 221–227. © Blackwell Munksgaard 2005. Abstract:
Hemoglobin (Hb) Q-Thailand [α74(EF3): Asp→His] is an abnormal Hb found mainly in China and South-east Asian countries. Association of the αQ-Thailand allele with α-thalassemia has important implications in diagnosis. We report the hitherto undescribed conditions of this variant in two unrelated pregnant Thai women. Routine Hb analyses using high-performance liquid chromatography identified abnormal Hb migrating after Hb A2 in addition to a homozygous Hb E in the proband 1 and to a heterozygous Hb Constant Spring (Hb CS) in the proband 2. Further α-globin gene analysis identified that the variant was caused by the GAC to CAC mutation at codon 74 of the α1-globin gene corresponding to the Hb Q-Thailand, detected in cis to the 4.2 kb deletional α-thalassemia 2 in both cases. Interaction of the αQ-Thailand with the βE globin chains in the proband 1 leads to a Hb variant, namely the Hb QE. Family study of the proband 1 showed that her non-pregnant sister had the same genotype but her father was a double heterozygote for Hb E and Hb Q-Thailand in whom both Hb Q-Thailand and Hb QE were detected. Genotype–phenotype relationships observed in these families with complex hemoglobinopathies are presented and compared with those of simple homozygote for Hb E, heterozygote for Hb CS and heterozygote for Hb Q-Thailand found in other unrelated subjects. A simple DNA assay based on allele-specific polymerase chain reaction for simultaneous detection of the Hb Q-Thailand mutation and the 4.2 kb deletional α-thalassemia 2 determinant was developed and validated.
Document Type: Research Article
Affiliations: 1: Department of Nutrition, Faculty of Public Health, 2: Clinical Microscopy Unit, Srinagarind Hospital, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
Publication date: March 1, 2005