40 Sickle Cell (Hemoglobin SS) Disease

Michelle To and Valentin Villatoro


β globin chain amino acid substitution in the 6th position from glutamic acid (Glu) to valine (Val). In the homozygous form of the disease, both β globin genes are affected.1



Autosomal dominant2



Tropical Africa

Mediterranean Areas


Sickle cell disease is common in areas where malaria is prominent and it is suggested that the disease acts as a protective factor for malaria. This protection is only seen in heterozygotes, as homozygotes often lose splenic function, which is essential for combating the parasite.


Cellular Features:1-4

See sickle cell (drepanocytes) under RBC morphology for more information about cell formation.


The formation of sickle cells becomes irreversible over time leading to the formation of rigid and “sticky” sickle cell aggregates resulting in many complications.



Chronic hemolytic anemia

Vaso-occlusion (can lead to ischemic tissue injury, splenic sequestration of RBCs, autosplenectomy)

Prone to infections




Laboratory Features of Sickle Cell Disease:2-4 


RBC: Decreased

WBC: Increased

PLT: Increased

Hb: Decreased

RETIC: Increased

RDW: Increased


Sickle cells

Normochromic, normocytic RBCs

Target cells



Howell-Jolly bodies

Pappenheimer bodies

Basophilic Stippling


Erythroid Hyperplasia

Iron stores: often increased

Hemoglobin Electrophoresis:

Hb S: 80-95%

Hb A: None

Hb A2: 2-%

Hb F: 5-20%

Other Tests:

Solubility Screen: Positive

Metasulfite Sickling Test: Positive


Hemoglobin Electrophoresis


1. Chonat S, Quinn CT. Current standards of care and long term outcomes for thalassemia and sickle cell disease. Adv Exp Med Biol [Internet]. 2017 [cited 2018 Jun 5];1013:59–87. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5720159/

1. Randolph TR. Hemoglobinopathies (structural defects in hemoglobin). In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p. 426-453.

3. Laudicina RJ. Hemoglobinopathies: qualitative defects. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p.231–50.

4. Harmening DM, Yang D, Zeringer H. Hemolytic anemias: extracorpuscular defects. 5th ed. Philadelphia: F.A. Davis Company; 2009. p. 250-79).


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Sickle Cell (Hemoglobin SS) Disease Copyright © 2019 by Michelle To and Valentin Villatoro is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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