The area of pallor contains a central accumulation of hemoglobin giving the appearance of a “target”. Look for macrocytosis that may imply liver disease; or if MCV is normal or low consider a hemoglobinopathy (HbC, D or E).

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Abnormal hemoglobin or abnormal hemoglobin synthesis

• Reduced hemoglobin formation: Thalassemias or Iron deficiency: Generally, target cells are more frequent in thalassemia than in iron deficiency. In some thalassemia e.g. HbE they are very frequent. Hypochromia and microcytosis will be present.
• Hemoglobinopathy: HbC, HbD and HbS . Target cells (together with irregularly contacted cells) are a major feature of HbC and HbD diseases, for HbS (or compound hemoglobinopathies e.g. HbSC) the target cells simply form part of the overall morphological syndrome. Cells will be normocytic or microcytic.

Causes related to membrane lipid

• Lipid disturbance e.g. related to liver disease: e.g. hepaticcirrhosis, alcohol. The excess membrane lipid produces macrocytic erythrocytes. Hyposplenic states. Reduced splenic conditioning results in excess membrane lipid. Other features of hyposplenism will be present. Inherited deficiency of lecithin-cholesterol acyl transferase. A very rare (but characteristic) inherited cause of target cells