• A large variation in shape of the erythrocytes is called poikilocytosis


  • Red cells with a loss of membrane leading to reduced diameter and decreased surface area but normal volume are called spherocytes. They are seen in hereditary spherocytosis, erythroblastosis and acquired hemolytic anemias.


  • Red cells varying in shape from elongated to oval, and rich in hemoglobin, are called elliptocytes/ovalocytes. They can be seen in hereditary disorders, such as hereditary elliptocytosis, or in acquired disorders, such as iron defiency anemia, infectious anemias, thalassemia, and in newborn babies.


  • Erythrocytes with a loosely folded, mouth-like pale area across the cell are called stomatocytes. They are seen in hereditary stomatocytosis, lead poisoning and thalassemia trait.


  • Fragmented cells showing bizarre poikilocytosis are called schistocytes. They can be seen in various forms of microangiopathic hemolytic anemia as well as after injury by mechanical means, e.g. through cardiac valve prostheses.


  • Schistocytes having one or more large horns around the perimeter are called keratocytes.

Helmet Cells

  • These are sharp-angled, helmet-looking cells seen in various anemias, e. g. thalassemia.


  • Spherocytical cells with large irregularly placed protrusions are called acanthocytes.


  • Red cells exposed to a hypertonic medium become wrinkled (crenated) with many small knoblike projections. They are called echinocytes.

Target Cells

  • Target cells, also known as Codocytes, have the hemoglobin concentrated in the middle and the periphery of the cell, and thereby resemble targets. They can be seen in hemoglobinopathies, e.g. thalassemias, and iron deficiency anemia.

Tear Drop Cells

  • Tear drop shaped red cells are also called Dacryocytes. They are seen when there is extramedullary erythropoiesis or with marrow disorders or marrow infiltration, such as myelofibrosis or metastatic carcinoma.

Sickle Cells

  • Sickle shaped cells are also called Drepanocytes. These cells take on a sickle-like appearance due to low oxygen tension. They are typically seen with hemoglobin S (sickle cell anemia).


  • As a result of losing a portion of the cell perimeter, these cells take on a bite-like appearance and are called degmacytes. They are seen in drug-induced hemolysis.

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