Known and new δ-globin gene mutations and other factors influencing Hb A2 measurement in the Omani population.

Although δ-thalassemia (δ-thal) is not categorized as a severe disease, it is essential to know the molecular spectrum of the δ gene mutations frequently occurring in specific areas, particularly if these areas are characterized by a high rate of β-thalassemia (β-thal) such as Oman. This is because coinherited δ-globin gene defects can interfere with the basic diagnosis of a β-thal carrier when this is based upon the measurement of the Hb A2 only. Because of that, we have investigated 33 patients with low Hb A2 levels, collected from different hospitals in Oman. Some cases had a second Hb A2 fraction, while others had only significantly lower Hb A2 levels. Among these patients, 20 did carry a δ-globin gene mutation, the rest were carriers of α thalassemia (α-thal) defects or could be iron depleted or both. In total, eight different known mutations and two novel δ variants were found. The characterization of the δ-globin gene mutation spectrum will improve carrier diagnostics and genetic counseling in the Omani population screened for β-thal.