Molecular Characterization of δ-Thalassemia in Iran

Abstract

δ-Thalassemia (δ-thal) (OMIM #142000) resulting from mutations on the HBD gene usually has no clinical consequences. However, it may cause the misdiagnosis of β-thalassemia (β-thal) carriers by lowering the Hb A₂ level to the normal range. Therefore, a study for δ-thal should be considered as a step in the detection of at-risk couple in our region. The aim of the present study was to characterize the mutations of the HBD gene in β-thal carriers with normal Hb A₂ levels, and also in normal individuals with Hb A₂ of less than 2.0%. Four β-thal carriers with normal Hb A₂ and 39 individuals with Hb A₂ of less than 2.0% were enrolled. Genomic DNA was extracted by the salting out method and the HBD gene was investigated by polymerase chain reaction (PCR) and direct DNA sequencing. Hb A₂-Yialousa (HBD: c.82 G > T) was the most common variant found in the HBD gene, but the following mutations were also found: Hb A₂-NYU (HBD: c.39 T > A), Hb A₂-Coburg (HBD: c.350 G > A), Hb A₂-Etolia (HBD: c.257 T > C), Hb A₂-Fitzroy (HBD: c.428 C > A) and the δ-IVS-I-5 (G > T) (HBD: c.92 + 5 G > T). One case was a compound heterozygote for δ-IVS-I-5/Hb A₂-Fitzroy. The results of this single center study suggest that the mutations in the HBD gene in the Iranian population are heterogeneous and should be considered in genetic counseling of families.

• δ-Thalassemia (δ-thal)
• Hb A₂
• Iran
• point mutation(s)

Acknowledgements

We would like to thank the individuals who participated in the study and staff of primary health care centers for their cooperation.

Declaration of interest

This research was supported by the Pasteur Institute of Iran, Tehran, Iran. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.