Hb Athens-Georgia (beta 40(C6) Arg > Lys, HBB:c.122G > A) with a single α-globin gene (Hb H disease) in a Thai family: molecular, hematological, and diagnostic aspects

Abstract

Interaction of structural hemoglobin (Hb) variants with α- or β-globin defects are occasional in Southeast Asia. Herein we provide the first description of Hb Athens-Georgia (Hb A-Ga) in association with deletional Hb H disease, a novel combination previously undescribed in the population. Hematological, Hb and DNA analysis, and β-globin haplotype analyses were performed in seven participants from one ethnic Thai family. Hemoglobin analysis by capillary electrophoresis revealed an abnormal Hb fraction in the proband, his father and grandmother (I-2). DNA sequencing revealed that the G > A substitution at codon 40 of the β-globin gene was identical to the Hb A-Ga (HBB:c.122G > A). Interestingly, α-thal-1 (SEA deletion) and α-thal-2 (-α^3.7 deletion) were identified in the proband resulting in Hb H disease, while α-thal-1 was identified in the father, and no α-thal was observed in I-2. Hematological analysis indicated that the proband (β^A-Ga/β^A, –^SEA/-α^3.7) had moderate anemia and was markedly hypochromic with microcytic red blood cells (RBCs). The father (β^A-Ga/β^A, –^SEA/αα) presented mild microcytic anemia, while normal hematology was observed in the I-2 who was heterozygous for Hb Athens-Georgia (β^A-Ga/β^A, αα/αα). The relative level of Hb A-Ga was distinctly reduced according to the degree of α-globin defects. The developed allele-specific PCR method can successfully be used for confirmation of Hb A-Ga. The Thai Hb A-Ga allele associated with a β-haplotype [+ - - - - - +]. These findings were in accordance with the previous conclusion that this variant is a non-pathological β-Hb variant.

Keywords:

• Hb Athens-Georgia
• Hb H disease
• α-thalassemia
• β-haplotype
• Thailand

Acknowledgements

The authors thank Adrian R. Plant for helpful comments on the manuscript.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Ethical approval

Ethical approval for the study protocol was obtained from the Institutional Review Board (IRB) of the University of Phayao, Phayao, Thailand (2/083/59). Informed consent was obtained from all individual participants included in the study.

Additional information

Funding

This research project was supported by a grant from the University of Phayao, Thailand (Grant no. RD61075).