Saturday, March 8, 2014

Target Cells (Codocytes)

Target Cells (Codocytes)

Background Information of Target Cells (Codocytes)

Target Cells (Codocytes) are RBCs that have the appearance of a shooting target with a bullseye. Under light microscope these cells appear to have a dark center (a central, hemoglobinized area) surrounded by a white ring (an area of relative pallor), followed by dark outer (peripheral) second ring containing a band of hemoglobin. 
Target cells are more resistant to osmotic lysis, which is mostly seen in dogs. Hypochromic cells in iron deficiency anemias also can show a target appearance.Target cells are abnormally resistant to saline.
Clinical Significance
  • Liver disease: Lecithin—cholesterol acyltransferase (LCAT) activity may be decreased in obstructive liver disease. Decreased enzymatic activity increases the cholesterol to phospholipid ratio, producing an absolute increase in surface area of the red blood cell membranes.
  • Iron deficiency: Decrease in hemoglobin content relative to surface area is probably the reason for the appearance of target cells. This is also seen in Thalassemias, Hemoglobin C disease, etc.
  • Alpha-thalassemia and beta-thalassemia (hemoglobinopathy)
  • Hemoglobin C Disease
  • Post-splenectomy: A major function of the spleen is the clearance of opsonized, deformed, and damaged erythrocytes by splenic macrophages. If splenic macrophage function is abnormal or absent because of splenectomy, altered erythrocytes will not be removed from the circulation efficiently. Therefore, increased numbers of target cells may be observed.
  • Autosplenectomy caused by sickle cell anemia

Cellular Description

RBCs that appear as a normal sized RBC but a larger than normal central pallor and a darkly-stained "lump" appearing in the middle synonymous to a bullseye (target)

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