Influence of Haptoglobin and Hemoglobin Phenotypic Polymorphisms on Sickle Cell Disease Morbidity

Abstract

Objectives: Sickle cell disease (SCD) has a varied clinical and biological expression depending on the hemoglobin phenotype: SSFA2, SFA2, SAFA2 and SC. Considering the antioxidant properties of the different haptoglobin phenotypes (Hp 1-1, Hp 2-1, Hp 2-2), it seemed relevant to know their influence on the morbidity of the different hemoglobin phenotype of SCD. Thus, the objective of this study was to identify associations between haptoglobin phenotype and morbidity of different SCD phenotypes. Methods: In a retrospective cross-sectional descriptive and analytical study, with a cohort of 170 black African carriers of hemoglobin S, in Ivory Coast, West Africa, hemoglobin and haptoglobin phenotypes were determined by electrophoretic methods. Results: The three major phenotypes of haptoglobin polymorphism were found in the SCD cohort: Hp 1-1 (24.1%), Hp 2-1 (56.5%), Hp 2-2 (19.4%). Vaso-occlusions were associated with haptoglobin phenotype Hp 1-1, (OR = 2.03; CI95% = [1.06 - 3.9]; p 2 (CI95% = [1.43 - 14.44]) and the probability of having the Hp 1-1 phenotype was lower (CI95% = [0.170 - 0.705]). Conclusions: Haptoglobin phenotype was associated to morbidity-adjusted hemoglobin phenotype. The study revealed a greater probability of a worse morbidity when the hemoglobin phenotype is homozygous. Unexpectedly, the worse morbidity is associated to Hp 1-1 haptoglobin phenotype, the most powerful antioxidant within the different haptoglobin phenotypes. Associations found were not systematic and need further studies to enlighten the determinism of SCD morbidity.