Development of a High Resolution Melting Curve Analysis for the Detection of Hemoglobin δ-Chain Variants in Thailand and Identification of Hb A2-Walsgrave [codon 52 (GAT>CAT), Asp→His; HBD:c.157G>C] in a Pregnant Woman from Southern Thailand

Phenotypic Expression of Known and Novel Hemoglobin A2-Variants, Hemoglobin A2-Mae Phrik [Delta 52(D3) Asp > Gly, HBD:c.158A > G], Associated with Hemoglobin E [Beta 26(B8) Glu > Lys, HBB:c.79G > A] in Thailand

“…Recently, another Hb variant caused by a mutation at the same position was identified, the non-pathological Hb A 2 -Walsgrave (δ52(D3) Asp > His; HBD:c.157G > C). This variant was found in the United Kingdom in a person who had emigrated from India [ 27 ] and had also been characterized in a pregnant Thai woman [ 15 ]. Moreover, five other δ-Hb variants have been documented in Thailand [ 12 , 13 , 14 , 16 ].…”

“…Identification of common α-thalassemia, including α-thalassemia 1 (SEA and THAI deletions), α-thalassemia 2 (−α 3.7 and −α 4.2 ), Hb constant spring (α CS ), and Hb Paksé (α Paksé ), mutations was performed routinely in our laboratory using the gap polymerase chain reaction (PCR) and allele-specific PCR (ASPCR) methods as previously described [ 18 , 19 , 20 ]. Hb A 2 -variants have previously been documented in Thai people, including the Hb A 2 -Melbourne (HBD:c.130G > A), Hb A 2 ’ (HBD:c.49G > C), and Hb A 2 -Lampang (HBD:c.142G > A) variants, which were identified using multiplex ASPCR [ 12 ], alongside the Hb A 2 -Walsgrave (HBD:c.157G > C) variant, which was determined by ASPCR [ 15 ]. The β E mutation at codon 26 (GAG to AAG) of the β-globin gene was investigated using an ASPCR method [ 21 ].…”

“…The actual epidemiology of δ-globin gene defects in Thailand has not been described. However, many δ-Hb variants have been identified, including Hb A 2 -Melbourne [δ43(CD2)Glu > Lys; HBD: c.130G > A] [ 11 ], Hb A 2 -Lampang [δ47(CD6)Asp > Asn; HBD: c.142G > A] [ 12 ], Hb A 2 -Kiriwong [δ77(EF1)His > Arg; HBD: c.233A > G] [ 13 ], Hb A 2 ’ [δ16(A13)Gly > Arg; HBD: c.49G > C] [ 14 ], Hb A 2 -Walsgrave [δ52(D3) Asp > His; HBD:c.157G > C] [ 15 ], Hb A 2 -Indonesia [δ69(E13) Gly > Arg; HBD:c.208G > C], and Hb A 2 -Troodos [δ116(G18) Arg > Cys; HBD:c.349C > T] [ 16 ]. Moreover, these variants have also been described in association with Hb E and α- or β-thalassemias [ 5 , 10 , 14 , 17 ].…”