What type of anemia is sickle cell anemia, specifically in individuals of African, Mediterranean, Middle Eastern, and South Asian descent?

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Classification of Sickle Cell Anemia

Sickle cell anemia is a chronic hemolytic anemia caused by an inherited genetic mutation in the beta-globin gene that produces abnormal hemoglobin S (HbS). 1

Type of Anemia

Sickle cell anemia is classified as a hemolytic anemia - specifically, a chronic inherited hemolytic anemia resulting from red blood cell destruction. 1, 2

Pathophysiologic Mechanism

The hemolysis occurs through the following mechanism:

  • Genetic mutation: A single nucleotide substitution (C to A) at codon 6 of the beta-globin gene replaces glutamic acid with valine, creating abnormal hemoglobin S (HbS, α2βs2). 1, 2

  • Polymerization and sickling: When deoxygenated, HbS molecules form polymers that cause red blood cells to deform into the characteristic rigid sickle shape. 1, 3

  • Red cell destruction: Extensive polymerization damages the red cell membrane and cytoskeleton, leading to formation of irreversibly sickled cells that undergo hemolysis. 1

  • Removal by reticuloendothelial system: Damaged red cells are removed by the spleen and other reticuloendothelial organs, resulting in chronic anemia. 1

Clinical Severity by Genotype

The severity of hemolytic anemia varies by genotype:

  • Severe forms (HbSS, HbSβ0-thalassemia, HbSD): Hemoglobin levels typically 60-90 g/L (6-9 g/dL), with 80-95% HbS and no normal HbA. 1, 4

  • Moderate forms (HbSC disease): Higher baseline hemoglobin with 50-55% HbS and 40-45% HbC. 1

  • Mild forms (HbSβ+-thalassemia): 10-25% HbA present with 70-80% HbS. 1

Additional Pathophysiologic Features

Beyond hemolysis, the disease involves:

  • Vaso-occlusion: Sickled cells adhere to vascular endothelium, causing ischemia-reperfusion injury and painful crises. 1, 3

  • Intravascular hemolysis: Leads to nitric oxide depletion and release of free heme, worsening vascular endothelial damage. 1, 5

  • Chronic inflammation: Repeated cycles of hemolysis, ischemia, and inflammation drive acute and chronic complications. 1, 6

Population Distribution

This inherited hemolytic anemia predominantly affects individuals of African or Caribbean descent (98% of UK cases), but is also seen in families from the Middle East, India, and the southern and eastern Mediterranean regions. 1, 7

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

4
Guideline

Sickle Cell Disease and Trait Pathophysiology

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

6
Research

Inflammatory targets of therapy in sickle cell disease.

Translational research : the journal of laboratory and clinical medicine, 2016

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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