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

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.

Hb Melusine and Hb Athens-Georgia: potentially underreported in the Belgian population? Four cases demonstrating the lack of detection using common CE-HPLC methods either for glycated hemoglobin (HbA1C) analysis or Hb variant screening

OBJECTIVE AND IMPORTANCE

Suspected hemoglobin (Hb) variants, detected during HbA_1C measurements should be further investigated, determining the extent of the interference with each method.

CLINICAL PRESENTATION

This is the first report of Hb Melusine and Hb Athens-Georgia in Caucasian Belgian patients. Intervention & Technique: Since common CE-HPLC methods for HbA_1C analysis or Hb variant screening are apparently unable to detect these Hb variants, their presence might be underestimated. HbA_1C analysis using CZE, however, alerted for their presence. Moreover, in case of Hb Melusine, even Hb variant screening using CZE was unsuccessful in its detection.

CONCLUSION

Fortunately, carriage of Hb Melusine or Hb Athens-Georgia variants has no clinical implications and, as shown in this report, no apparent difference in HbA_1C should be expected.