Target cells (codocytes) can be found in the peripheral blood in a number of conditions. In vivo the cell has a bell-shaped appearance. The cell either has a relative increase in the amount of membrane or a decrease in hemoglobin content, which is associated with an increased ratio of RBC surface area to volume.
A target cell is an erythrocyte with:
(1) a central hemoglobinized area
(2) surrounded by a ring of pallor
(3) which in turn is surrounded by a hemoglobinized ring extending to the cell membrane
Conditions associated with target cells:
(1) hemoglobinopathies (thalassemias, hemoglobin C, hemoglobin D, hemoglobin E, sickle cell disease)
(2) familial hypobetalipoproteinemia
(3) liver disease
(4) iron deficiency anemia
(5) status post splenectomy
(6) lead poisoning
Target cells may also be an artifact of smear preparation.
