The impact of the coinheritance of alpha thalassemia and hemoglobin f concentration on sickle cell disease

Alpha thalassemia and hemoglobin F concentration are major modulators of sickle cell disease in many populations. To address the impact of these two modulators on phenotype in sickle cell disease patients from Northern Iraq this study was initiated. Seventy-four Iraqi patients with sickle cell anemia or sickle/beta 0 thalassemia in steady state were enrolled. They had a median age of 16 years and included 56.8% males. Patients were clinically evaluated and had their blood and reticulocyte counts, hemoglobin F, serum lactic dehydrogenase, and bilirubin assayed. Furthermore, they were screened for alpha-thalassemia mutations by multiplex PCR and reverse hybridization. Hemoglobin F was positively correlated with hemoglobin, negatively correlated with reticulocyte count, hemoglobin A2, and blood transfusion frequency (P=0.033, 0.041, 0.037, and 0.02 respectively), but it was not correlated to other clinical manifestations. Alpha thalassemia was detected in nine patients (including eight with -alpha 3.7/alpha alpha and one with -alpha 4.2/alpha alpha), but it did not show any significant hematological or clinical associations. The current study revealed that among SCD patients from Northern Iraq, hemoglobin F and not alpha-thalassemia had a modulating effect on phenotype, which is in contrast to the situation among SCD patients from Africa, the Arabian Peninsula, and Southern Iraq, where alpha-thalassemia plays an important modulatory role, sometimes even exceeding HbF.