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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Cite this: Emmanuel C. Besa, Sophie M. Lanzkron. Fast Five Quiz: Are You Prepared to Confront Sickle Cell Disease? - Medscape - Sep 23, 2021.