What are burr cells?

Burr Cells (Echinocytes): Definition and Clinical Significance

Burr cells (echinocytes) are abnormally shaped red blood cells with multiple, evenly spaced projections on their surface, giving them a crenated appearance that can be identified on peripheral blood smear examination. 1

Morphological Characteristics

• Burr cells have multiple, evenly spaced projections on their surface, creating a characteristic crenated appearance that distinguishes them from normal erythrocytes 1
• These cells maintain their overall round shape but display uniform spiculations around their periphery, unlike other abnormal red cell forms 2
• They can be readily identified during routine peripheral blood smear examination as part of a complete blood count workup 1

Pathophysiological Mechanisms

• Formation of burr cells primarily results from alterations in red blood cell membrane composition, particularly due to:
  • Changes in phospholipid membrane asymmetry due to oxidative stress 2
  • Alterations in phosphatidylserine and phosphatidylinositol concentrations in the cell membrane 3
  • Accumulation of uremic toxins affecting membrane structure 2
  • Effects of hyperbilirubinemia triggering eryptosis (programmed death of erythrocytes) 2

Clinical Significance and Disease Associations

• Burr cells are a significant independent predictor of 30-day mortality, associated with a 3-fold increase in risk of death when present on admission 4
• The presence of burr cells is strongly associated with:
  • Liver disease and hepatic failure, where bile acids and bilirubin directly affect red cell membrane structure 2
  • Chronic kidney disease and uremia, where uremic toxins stimulate eryptosis 2
  • Alcoholic liver disease, where both direct alcohol effects and progressive hepatic injury alter membrane lipid composition 3
  • Microangiopathic hemolytic anemia, where they serve as a diagnostic indicator 1

Laboratory Evaluation

• When burr cells are identified, the following investigations should be performed:
  • Complete blood count with peripheral smear review to confirm burr cell presence and quantify their percentage 1
  • Hemolysis workup including LDH, haptoglobin, and indirect bilirubin 1
  • Liver function tests to assess for hepatic dysfunction 2
  • Renal function tests to evaluate for uremia 2

Management Implications

• The presence of burr cells should prompt investigation of underlying conditions, particularly liver and kidney dysfunction 2
• Treatment should focus on addressing the underlying cause:
  • In alcoholic liver disease, cessation of alcohol intake may normalize hematological parameters, though burr cells may persist 3
  • In uremia, optimization of dialysis may reduce uremic toxins and associated burr cell formation 2
  • In cases associated with parenteral nutrition, particularly fish oil supplementation, discontinuation of the offending agent may resolve the anemia 5

Prognostic Value

• The presence of burr cells on admission is associated with a mortality rate of approximately 27.3%, particularly in patients with renal or liver failure 4
• Regular monitoring of complete blood count and peripheral smear is recommended until resolution of the underlying condition 1
• Burr cells should be recognized as a marker of severe underlying disease that requires prompt evaluation and management 1