Sickle Cell Disease in a Patient with Sickle Cell Trait and Compound Heterozygosity for Hemoglobin S and Hemoglobin Quebec–Chori

Abstract

THE sickle cell trait is generally considered to be benign, because the presence of hemoglobin A in a concentration of more than 50 percent in the red cells of persons heterozygotic for hemoglobin A and hemoglobin S (hemoglobin A/S) prevents the polymerization of the remaining hemoglobin S under physiologic conditions.¹ Occasional reports suggest, however, that after extreme physical stress or hypoxia, the sickle cell trait can be associated with serious morbidity and even death.^{2 4} In most cases, the diagnosis of this trait is straightforward: hematologic measures such as hemoglobin, hematocrit, red-cell indexes, and the reticulocyte count are normal, and electrophoretic techniques demonstrate the presence of hemoglobin A and hemoglobin S. A solubility test is used to confirm that the hemoglobin migrating in the "S" position is sickle hemoglobin. Since electrophoretic techniques separate hemoglobins on the basis of their net charge, any variant that has a net charge similar to that of either hemoglobin A or hemoglobin S will not be identified. We report a case in which unexplained clinical symptoms suggestive of sickle cell disease were seen in an apparent carrier who proved to have such an "electrophoretically silent" variant.