Sickle Cell Disease in Jordan: The Experience of a Major Referral Center

INTRODUCTION: Sickle cell disorders are the most frequently encountered hemoglobin variants in Jordan. Both alpha and beta thalassemias are also prevalent in this population. However, studies on the interaction between these hemoglobin disorders are lacking. AIM: To determine the genotypes responsible for Sickle cell disease in Jordan, by retrospectively reviewing the data from a major referral center in the country’s capital. METHODS: A total 29,712 peripheral blood samples referred and investigated for hemoglobinopathies over a 10-year period at Princess Iman Center at Amman, Jordan were retrospectively reviewed. In addition to full blood counts, high performance liquid chromatography, those who were identified with sickle cell hemoglobin were studied using polymerase chain reaction and reverse hybridization to determine the various sickle cell disease genotypes. RESULTS: Out of the (29,712) blood samples, 450 were sickle cell trait, while 216 had sickle cell disease. Of the latter: 120 were found to be cases of Sickle cell anemia (Hb SS), 66 were compound heterozygous for Sickle cell and a beta thalassemia mutation (Sickle/β-thalassemia), while 30 had concomitant alpha thalassemia (HbSS/alpha thalassemia). The most frequent genotype associated with sickle/β-thalassemia was HbS/ IVS-110 (G>A), followed by Hb S/IVS-I-6 (T>C), HbS/IVS-II-745 (C>G) and HbS/ IVS-II-1 (G>A). While the most frequent alpha genotype detected in HbSS/α-thalassemia samples was (-α(3.7)/αα) followed by (-α(3.7)/-α(3.7)). Hb SS patients had the severest hematological phenotype compared to those with sickle/β-thalassemia and sickle/ α-thalassemia. Furthermore, within the sickle/β-thalassemia subgroup the least severe hematological phenotype was encountered in HbS/IVS-1-6 (T>C), while the most severe in HbS/IVS-II-1 (G>A) genotype. CONCLUSION: The most frequent Sickle cell disease genotype in Jordanians is Sickle cell anemia (HbSS), followed by Sickle/β-thalassemia and least frequent is HbSS/alpha thalassemia. The concomitant identified thalassemia mutations were consistent with their spectrum among the Jordanian population.