Fast Five Quiz: Are You Prepared to Confront Sickle Cell Disease?

Emmanuel C. Besa, MD; Sophie M. Lanzkron, MD, MHS


September 23, 2021

Figure 1. Sickle red blood cell.

SCD refers to all genotypes containing at least one sickle gene, in which HbS makes up at least half of the hemoglobin present. Major sickle genotypes described so far include:

  • HbSS disease or sickle cell anemia (the most common form): Homozygote for the S globin with usually a severe or moderately severe phenotype and with the shortest survival

  • HbS/b-0 thalassemia: Compound heterozygote for HbS and b-0 thalassemia; clinically indistinguishable from sickle cell anemia (SCA)

  • HbS/b+ thalassemia: Mild-to-moderate severity with variability in different ethnicities

  • HbSC disease: Compound heterozygote for HbS and HbC characterized by moderate clinical severity

  • HbS/hereditary persistence of fetal Hb (S/HPHP): Very mild or asymptomatic phenotype

  • HbS/HbE syndrome: Very rare, with a phenotype usually similar to HbS/b+ thalassemia

  • Rare combinations of HbS with other abnormal hemoglobins such as HbD Los Angeles, G-Philadelphia, HbO Arab, and others

Learn more about the genetics of SCD.


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