Association of Hb Shenyang [α26(B7)Ala→Glu, GCG>GAG, HBA2: c.80C>A (or HBA1)] with Several Types of α-Thalassemia in Thailand

Abstract

Hb Shenyang [α26(B7)Ala→Glu, HBA2: c.80C>A (or HBA1)] is a rare α chain variant. Its genotype-phenotype relationship and origin have not been described in Thailand before. Three Thai subjects (P1–P3) carrying this variant were studied. Hemoglobin (Hb) analysis was performed by capillary electrophoresis (CE) and high performance liquid chromatography (HPLC) as well as molecular characterization using appropriate polymerase chain reaction (PCR) techniques and DNA sequencing. Hemoglobin analysis by HPLC revealed fast-moving abnormal peaks at a retention time (RT) of 1.59–1.62 min., while CE revealed a fast-moving abnormal Hb at zone 12 and ahead of Hb A₂ in three subjects. DNA analysis revealed a C>A transition at codon 26 of the α2-globin gene glutamic acid to replace alanine, corresponding to Hb Shenyang. The Southeast Asian [– –^SEA α-thalassemia-1 (α-thal-1)] deletion was also identified in P1 and his mother, while Hb Constant Spring (Hb CS, HBA2: c.427T > C) was identified in P2. The Hb Shenyang concentration measured by CE revealed 5.1–17.2% heterozygosity with normal red blood cell (RBC) parameters. The α haplotype [+ – S + – + –] [S signifies the inter ζ hypervariable region (HVR)] was associated with the Thai Hb Shenyang. The genotype-phenotype relationship indicates Hb Shenyang is likely a non pathological Hb variant that has neither dramatic clinical symptoms nor hematological anomalies. A simple multiplex allele-specific PCR for rapid diagnosis of Hb Shenyang has been developed.

Keywords:

• Abnormal hemoglobin (Hb)
• α-thalassemia (α-thal)
• Hb Shenyang
• northern Thailand

Disclosure statement

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

Additional information

Funding

This research project was supported by a grant from the University of Phayao, Phayao, Thailand [Grant #RD61075].