Molecular Characterization of α-Thalassemia in the Dohuk Region of Iraq

Abstract

The molecular basis of α-thalassemia (α-thal) has been addressed by several studies from the eastern Mediterranean region, but not from Iraq. To address this issue, we studied 51 individuals with unexplained hypochromia and/or microcytosis, as well as nine patients with documented Hb H disease from the Dohuk region in northern Iraq. We used multiplex gap-polymerase chain reaction (gap-PCR), reverse hybridization, and sequencing for this purpose. It was found that the most common genotypes in those with unexplained hypochromia and/or microcytosis were −α^3.7/αα, followed by − −^MED-I/αα, then −α^3.7/−α ^3.7, respectively, detected in 84.3% of the above individuals. Other genotypes identified sporadically were −α^4.2/αα, α^{poly A1}α/αα (AATAAA>AATAAG), α^Adanaα/αα [Hb Adana, codon 59 (Gly→Asp) or HBA1:c.179G>A], and α^Evanstonα/αα [Hb Evanston, codon 14 (Trp→Arg) or HBA1:c.43 T>C]. Three cases (5.88%) remained uncharacterized even after sequencing. All nine Hb H cases carried the −α^3.7/− −^MED-I genotype. Such findings are rather different from those in other eastern Mediterranean populations, particularly with relevance to an Hb H molecular basis.

Keywords:

• α-Thalassemia (α-thal)
• −α^3.7/
• − −^MED-I
• Hb Evanston
• Hb Adana
• Iraq
• Dohuk