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The page below is a sample from the LabCE course Red Blood Cell (RBC) Morphology. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Red Cell Variations in Shape

RBC variations in shape are listed in the tables below along with associated conditions. The morphological variations in red blood cell shape that are shown in Table 1 have clinical significance, even in low numbers and should be identified and reported regardless of the frequency of observation on the smear.

Table 1

Cell Name


Possible Significance


Abetalipoproteinemia, cirrhosis

Fragmented cells

Includes these specific types of cells:

  • Schistocyte
  • Prekaratocyte (blister cell)
  • Keratocyte(helmet cell, horn cell)

Evidence of mechanical damage to the red blood cells.

Disseminated intravascular coagulation (DIC), severe burns, septicemia, certain drugs, thrombotic thrombocytopenic purpura (TTP)

Sickle cell (Drepanocyte)
Sickle cell anemia
SpherocyteHereditary spherocytosis, some hemolytic anemias
Teardrop (Dacrocyte)
Thalassemia, hemolytic anemia, myelofibrosis

Other morphological variations in red blood cell shape have little significance when seen in very low numbers and are clinically relevant when their presence is more obvious. These variations in shape that are significant only if observed in large numbers on the smear are listed in Table 2.

Table 2

Cell Name


Possible significance (In large numbers)

Echinocyte (Burr cell)


Elliptocytes / ovalocytes Hereditary elliptocytosis
StomatocytesHereditary stomatocytosis, acquired hemolytic anemias
Target cells (Codocytes)
Thalassemia, retention jaundice