erythrocyte morphologic features

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The following table contains a list of terms that are commonly used to describe various erythrocyte morphologic features and an interpretation of these terms.   Anytime a highlighted blue word is observed, click on this term to see additional information.
 

Polychromasia: Polychromatophylic erythrocytes are those that show a faint bluish tint due to an admixture of the characteristic colors of hemoglobin and the basophilic erythrocyte cytoplasm when stained with a Romanowsky stain or a quick stain. Many of these would be reticulocytes if stained with new methylene blue.  Polychromasia is an indicator of regenerative anemia.
Reticulocyte: A reticulocyte is any non-nucleated cell of the erythrocytic series containing RNA, which when stained with new methylene blue will have discernible granules or have a diffuse network of fibrils. They are the hallmark of erythrocyte regenerative response.
Nucleated Erythrocytes: Nucleated red blood cells are commonly observed in regenerative anemias, but may also be observed in non-anemic or non-regenerative anemic states such as lead poisoning, hypoxia, or myeloproliferative disease in cats.
Howell-Jolly Bodies: HJ bodies are nuclear remnants observed in young erythrocytes. A few are often observed in red cells of cats and horses. They can be observed in regenerative anemias of most animals. They may be observed in splenic disease or in the absence of a spleen, since the spleen normally removes HJ bodies from red cells
Macrocytosis: Macrocytes are erythrocytes that are larger than normal. In the presence of regenerative anemias they represent immature non-nucleated red cells. They may also be observed in feline leukemia virus-induced disease of red cells in cats. They are occasionally observed as a congenital dyserythropoiesis in the poodle.  These animals will have a MCV greater than the reference range.	.
Anisocytosis: Anisocytosis simply describes the observation of erythrocytes that are smaller or larger than normal along with normally sized-erythrocytes. Anisocytos is observed in regenerative anemias or iron deficiency anemias.
Basophilic Stippling: Basophilic stippling is observed in erythrocytes stained with Romanowsky stains such as the quick stains. They are erythrocytes that contain abnormal aggregation of RNA that usually only stains with new methylene blue. It can be observed in heavy metal poisoning in the presence of non-regenerative anemias, or in intense erythrogenesis in dogs, cats and ruminants along with polychromasia.
Normocytes: Normocytes are normally sized and shaped erythrocytes defined morphologically by the MCV or mean cell volume. The MCV varies with each species:  Dog: 60-77 fl,         Cat: 39-55fl,          Horses:  34-58fl          Cattle:  40-60fl   A normal dog is shown at right
Microcytes: Microcytes are erythrocyes which have a smaller size than normal as determined by observation or calculation of the Mean Cell Volume. An MCV below the suggested reference range suggests microcytosis. Microcytes are commonly observed in iron deficiency anemia as caused by chronic blood loss or parasitism.
Hypochromasia. Hypochromic erythrocytes are those that have a decreased density of the characteristic hemoglobin color as observed or by calculation of the Mean Corpuscular Hemoglobin Concentration(MCHC). Hypochromasia is frequently observed in iron deficiency anemia as caused by chronic blood loss or parasitism.
Spherocytes: Spherocytes are spheroid rather than biconcave disk-shaped erythrocytes. They have a reduced amount of cell membrane and a hyperchromatic color. They are seen most frequently in autoimmune, isoimmune or microangiopathic hemolytic anemias, and recognized mainly in the dog.
Heinz Bodies: Heinz bodies are particles of denatured hemoglobin protein. They stain with new methylene blue buy appear as colorless "bumps" on a Romanowsky or quick stain. They may be caused by oxidant drugs and chemicals. Heinz bodies may be observed in 2-3% of the erythrocytes of normal cats. In dogs, oxidative injury is often associated with the presence of eccentrocytes.
Crenation. Crenation is identified as the presence of many regular membrane projections involving most of the cells. It is usually an artifact due to slow drying of the blood film. It is commonly observed in blood films from pigs, but can also be observed on blood films from normal cats and cattle.
Poikilocytes: Poikilocytes or schistocytes are erythrocytes having an abnormal shape. Schistocytes are observed in fragmentation hemolysis caused by DIC, vascular neoplasia, endocarditis, and may also be observed with iron deficiency anemia.
Acanthocytes: Acanthocytes are erythrocytes having irregular projections from the surface. They have been observed in dogs and cats with severe liver disease and are probably the result of alteration of lipid content of the red cell membrane.
Target Cells and Folded Cells. These are two types of leptocytes observed mainly in dogs. They represent cells with an increased membrane-to-volume ratio. The change is not specific for any particular disease.  A target cell and a folded cell are seen in the center.  Leptyctes have a cell membrane that is thin and flimsy.  Because of this they may take on abnormal configurations as shown here.
Rouleaux. Rouleaux is a term used to describe erythrocytes that are in the form of a stack of coins that has been pushed over. Rouleaux is commonly observed in normal horses and to a lesser extent normal cats. It can also be observed with increased immunoglobulins. Grossly, rouleaux must be differentiated from autoagglutination . Rouleaux is dispersed in blood washed with saline but autoagglutination is not.
Autoagglutination: Autoagglutination is an irregular clumping together of red cells caused by the presence of anti-red cell antibody. It must be distinguished from rouleaux.
Hemobartonella felis: A ubiquitous red cell parasite of cats.
Hemobartonellosis in a cat
Anaplasmosis in a cow
Hemobartonellosis in a dog
Normal Equine blood film:  Normal equine erythrocytes have a little central pallor but rouleaux is common and normal.  The tendency of equine erythrocytes to rouleaux is so dramatic that a marked sedimentation can be observed in an EDTA-collected sample in just minutes.  The normal life span of equine erythrocytes is about 145 days and their diameter is about 5 microns.
Normal Feline blood film:  Normal feline erythrocytes have little to no central pallor because the bi-concave structure of their erythrocytes is not as marked as that of canine erythrocytes.  Rouleaux and some degree of crenation are common features.  The red cell diameter is about 5 microns and the red cell life span is about 70 days.
Normal Bovine blood film:  Normal bovine erythrocytes are often crenated.  They are similar in deameter to feline and equine erythrocytes and have a life span of about 150 days.  Slight anisocytosis is sometimes observed.	.
Babesia Canis - Typical pearshaped organisms
Babesia Gibsoni - small babesia observed at first in pit bull-type dogs and now appearing in other species
Leishmania - Currently being observed in Fox Hound in the United States
Diphasic Sedimentation rate in the horse indicating a regenerative anemia