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
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.
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
Normochromic, normocytic RBCs
Iron stores: often increased
Hb S: 80-95%
Hb A: None
Hb A2: 2-%
Hb F: 5-20%
Solubility Screen: Positive
Metasulfite Sickling Test: Positive
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).