SCD Causes a Mutation in the Hemoglobin Structure

The Type of SCD Depends on the Mutation

Sickle Cell Traits vs SCD Genotypes1,3-6

Sickle Cell Trait
Sickle cell trait graphic

Individuals with sickle cell trait inherit 1 mutant allele (Hbs)

  • ~8% of African Americans are sickle cell trait carriers1
Sickle Cell Anemia
Sickle cell anemia graphic

Individuals with sickle cell anemia inherit 2 HbS alleles

  • ~74%-76%* of SCD population4,5
  • ~70% are of African ancestry4,5
Other SCD Genotypes
Other SCD genotypes graphic

Individuals inherit 1 HbS allele and another mutant Hb allele

5 different subtypes, depending on other mutation

  • HbSC represents ~18%-24% of SCD population4,5*
    • ~25%-30% are of African ancestry
  • HbSβ0-thalassemia represents ~1%-6% of SCD population4,5*
    • Most prevalent in people of Eastern Mediterranean or Indian descent
  • HbSβ+-thalassemia represents ~1%-6% of SCD population4,5*
    • Most prevalent in people of Eastern Mediterranean or Indian descent
  • HbSD represents 1.3% of SCD population5*
    • Most prevalent in northern India but occurs worldwide
  • HbSα-thalassemia6
    • ~40% are of African ancestry
    • ~45% are of South East Asian ancestry



1. Steinberg MH. Sickle cell disease and associated hemoglobinopathies. In: Goldman L, Ausiello D, eds, Cecil Medicine, 23rd ed. Philadelphia, PA; Saunders Elsevier; 2008:1217-1226. 2. Kalpatthi R, Novelli EM. Measuring success: utility of biomarkers in sickle cell disease clinical trials and care. Hematology Am Soc Hematol Educ Program. 2018. 2018;2018(1):482-492. 3. Piel FB, Steinberg MH, Rees DC. Sickle cell disease. N Engl J Med. 2017;376(16):1561-1573. 4. Rees DC, Williams TN, Gladwin MT. Sickle-cell disease. Lancet. 2010;376(9757):2018-2031. 5. Saraf SL, Molokie RE, Nouraie M, et al. Differences in the clinical and genotypic presentation of sickle cell disease around the world. Paediatr Respir Rev. 2014;15(1):4-12. 6. Hassell KL. Population estimates of sickle cell disease in the U.S. Am J Prev Med. 2010;38(4 Suppl):S512-S521.

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