ERYTHROCYTE MORPHOLOGY

2 ERYTHROCYTE MORPHOLOGY



Shannon Jones Hostetter, Claire B. Andreasen



1 What are Howell-Jolly bodies, and when do they usually occur?


Howell-Jolly bodies are remnant portions of nuclear material that are found within the cytoplasm of erythrocytes. These bodies are basophilic and spherical. Howell-Jolly bodies are usually observed with accelerated erythrocyte production or after splenectomy.



2 What are Heinz bodies, and what causes them?


Heinz bodies are precipitates of denatured hemoglobin attached to the erythrocyte membrane. These bodies occur following oxidation of hemoglobin. Heinz bodies are found in low numbers in health in certain species (e.g., cat) or may be associated with hemolytic anemias (Figure 2-1).


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Figure 2-1 Peripheral blood smear stained with Wright’s from a cat with Heinz body anemia. The arrows indicate Heinz bodies on the erythrocyte surface.



3 How are Howell-Jolly and Heinz bodies distinguished morphologically?


Although both structures are round, Howell-Jolly bodies are basophilic and located deeper within the cytoplasm than Heinz bodies, which protrude from the red blood cell (RBC) surface. Also, Heinz bodies on Wright’s stain are the same color as the erythrocyte’s cytoplasm because they are derived from hemoglobin.



4 What is the cause of basophilic stippling in erythrocytes, and when does it occur?


Basophilic stippling results from minute aggregations of residual ribonucleic acid (RNA) that collect within the cytoplasm of the erythrocyte and is an indicator of RBC immaturity. Stippling is readily observed with either Wright’s or Diff-Quik staining. Basophilic stippling is occasionally observed in anemic cats and indicates a regenerative response. Basophilic stippling with polychromasia and anemia may be an appropriate response to the anemia. An inappropriate basophilic stippling response occurs in lead toxicosis, in which there is increased basophilic stippling, as well as metarubricytosis, with variable polychromasia.



5 Define anisocytosis and identify associated conditions.


Anisocytosis is variation in cell size. Although mild anisocytosis can be observed in erythrocytes from healthy dogs and cats, more pronounced anisocytosis is associated with a variety of conditions. These include regenerative anemias, some hemolytic anemias, Heinz-body anemia, and breed-associated variations in RBC size (see Question 29).



6 What are macrocytes and microcytes?


Macrocytes are larger erythrocytes of normal shape.


Microcytes are abnormally small erythrocytes.



7 What are spherocytes?


Spherocytes are small, spherical erythrocytes that lack central pallor. Spherocytes are more easily observed in the dog; dogs normally have erythrocytes that are slightly larger than other domestic animals, and dog erythrocytes have well-defined central pallor. Rare spherocytes may be seen in circulation before being removed by the liver or spleen, since immunoglobulin G (IgG) increases on the surface of “old” erythrocytes. This is the process by which old erythrocytes are removed from circulation (see Figure 1-2).



8 How are spherocytes formed?


Spherocytes are formed when macrophages within the liver and spleen remove a portion of a damaged erythrocyte’s cell membrane. This generally occurs after the erythrocyte’s surface has been coated with either antibody or complement. Because a portion of the membrane is removed, the resulting RBC has reduced cell membrane surface area relative to cytoplasmic volume. Therefore, spherocytes appear as smaller, dense cells that lack central pallor.



9 Spherocytes are typically associated with what disease?


Spherocytes are associated with immune-mediated hemolytic anemia (IMHA). Spherocytes also occur as part of a natural aging process, but then are seen only in low numbers in circulation.



10 Define polychromasia and explain its significance.


Polychromasia is the variation in cell staining (change to bluish gray) observed in erythrocytes stained with Romanowsky-type stains due to the presence of residual RNA. Polychromasia is used as an index of regeneration in anemia because all polychromatophilic erythrocytes are reticulocytes; however, not all reticulocytes have enough reticulin to be polychromatophilic.



11 What is a poikilocyte?


Poikilocytes are abnormally shaped erythrocytes. Poikilocyte is a general term used to describe any specific change in shape in an erythrocyte.



12 What are leptocytes, and with what conditions are they associated?


Leptocytes are thin erythrocytes with an increased amount of cell membrane relative to the total cell volume; thus they are folded over. Because polychromatophilic erythrocytes are often larger with more membrane, many leptocytes may be observed during increased erythrocyte turnover. Leptocytes also may be present with liver diseases such as portosystemic shunts in the dog. Target cells are a type of leptocyte (see Question 13).

Related posts:

  1. ERYTHROCYTE DISORDERS
  2. OVERVIEW: HEMOSTATIC COMPONENTS AND DISORDERS
  3. INTERPRETATION OF THE LEUKOGRAM
  4. AVIAN BIOCHEMICAL ANALYSIS

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Aug 26, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on ERYTHROCYTE MORPHOLOGY

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