Molecular Characterization of Alpha and Beta Thalassemia in Yemeni Sickle Cell Disease Children

Abstract

There are no previous reports about the molecular defects of alpha and beta thalassemia in Yemeni sickle cell disease (SCD) patients, except one report about alpha thalassemia in Yemeni SCD children living in Riyadh Saudi Arabia. The aim of this clinical cross-sectional study was directed to determine the genetic defects of α and β- thalassemia in Yemeni sickle cell disease children and to determine their prevalence in Taiz governorate Yemen where the prevalence of sickle-cell trait HbAS is about 8.2%. Blood samples were collected from 145 SCD children to determine the complete blood count, sickling tests and hemoglobin fraction analysis by high pressure liquid chromatography (HPLC) method. Serum ferritin was determined in serum of those patients who had low mean cell volume (MCV) and low mean cell hemoglobin (MCH) to exclude presence of iron deficiency anemia. The DNA was analyzed in 30 patients with thalassemia indices after exclusion of iron deficiency anemia using polymerase chain reaction (PCR) based techniques namely (The β- Globin and α-globin test Strips assay and Gap PCR). This study showed that in Taiz governorate the overall prevalence of SCD with thalassemia was (27.5%) and according to DNA analysis the prevalence of ( HbSS+α-thalassemia) and (HbS/β0- thalassemia) were 18.5% and 5.9%, respectively. For first time in Taiz and Yemen the present study confirms presence of different combination between sickle cell gene, β0- Thalassemia and α-Thalassemia genes which means presence of these genetic diseases in Yemeni population. There were 8 patients (26.6%) with (βS/ β0) - thalassemia and 22 (73.3%) with (HbSS/ α�thalassemia). There were three β thalassemia mutations detected the most common mutation was the ( IVS II-1 A>T ) type with frequency of (75%), and the α-thalassemia deletion found in Yemeni SCD children was of right ward deletion (-3.7 kb), and 17 patients (68%) had one gene deletion and 8 patients (32%) two gene deletions.