Terms related to RBC size
Anisocytosis variation in cell size, can be either small or large.
Microcyte small cells, decreased MCV. These are commonly seen in iron deficiency or in anemia of chronic or inflammatory
disease. Microcytosis is often present in portosystemic shunts. Microcytosis is normal in Akita and Japanese Shiba dogs.
Macrocyte large cells, increased MCV. These are usually immature cells (reticulocytes) seen in regenerative anemias. Mild
macrocytic, hypochromic anemia has been observed in Alaskan Malamutes with hereditary chondrodysplasia and stomatocytosis.
FeLV infection can cause macrocytosis through altered erythrocyte maturation and is often associated with myelodysplastic
or myeloproliferative diseases. Miniature and toy poodles occasionally are recognized with macrocytosis. These dogs may
have other changes including hypersegmented neutrophils, multiple Howell Jolly bodies or nRBCs with fragmented nuclei but
tend not to have clinical signs (e.g. anemia) associated with these changes. ±2, cobalamin and/or folic acid deficiency can
induce a megaloblastic anemia. Cobalamin deficiency has been reported in dogs (Giant Schnauzers, Border Collies, Beagles,
and Australian Shepherds) and cats.
Terms related to RBC color
Polychromasia bluish red cells. These are usually large and represent reticulocytes as seen in regenerative anemias.
Hypochromasia pale colored cells with increased central pallor caused by insufficient hemoglobin in the cell. This can be
due to iron deficiency or to anemia of chronic or inflammatory disease. Reticulocytes often appear hypochromic because they
are undergoing hemoglobinization.
Hyperchromasia cells with increased staining intensity
Terms related to RBC shape
Poikilocytes abnormally shaped red cells. Although this is a general term referring to any abnormally shaped red cell, it
if often used to describe cells that can't be specifically described as below.
Acanthocyte (spur cell) spiculated red cell with single or multiple, blunt, rounded projections. These are associated with
microangiopathy and fragmentation anemia (dogs especially) and liver disease (more in cats). The latter is due to excess
cholesterol:phospholipids ratio in the RBC membrane.
Burr cell red cells that resemble acanthocytes but are usually more elongate with less pronounced surface spikes. Associated
with kidney disease.
Crenation (also referred to as echinocytes) red cells with even distribution of sharp spikes. An artifact of old blood,
delayed drying of the blood film, improper anticoagulant ratio. Shape change occurs in all cells in given area of blood smear.
Dacrocyte teardrop shaped RBC. Associated with myelofibrosis and myeloproliferative disorders.
Drepanocyte sickled RBC (may be seen in deer, sheep and goats.
Eccentrocyte (pyknocyte) - red cell with condensed hemoglobin in one area of the cell. These occur due to oxidative damage
to the hemoglobin.
Echinocyte - spiculated red cell with numerous short, evenly spaced surface projections. Three types exist based on the sharpness
of the spicules. Type 3 has a very prickly spine appearance and is associated with snake bite envenomation in dogs. Types
1 and 2 are more blunt, may be due to electrolyte abnormalities, dehydration, or sample or slide artifact (e.g. crenation).
Elliptocyte oval shaped RBC. This is the normal shape for erythrocytes from some non-domestic species including camelid,
avian, reptile, and fish erythrocytes.
Ghost cells – Pale or indistinct erythrocytes that have undergone lysis but still retain some membrane.
Keratocyte (helmet cell) - a spiculated red cell with one or 2 pointed projections. It results from the rupture of a vacuole
formed near the cell surface and are frequently seen, in association with other fragments, in iron deficiency anemia but can
also be seen in other processes of mechanical damage.
Leptocytes thin cells with increased membrane surface are compared to its contents, may appear shaped like target cells,
Mexican hats, or folded bowls. Polychromatic leptocytes are generally reticulocytes. If leptocytes are mature red cells,
it suggests alteration of cell morphology by disease.
Schistocyte (schizocyte) fragmented red cell. These are associated with intravascular trauma to the erythrocyte, especially
due to DIC but also to microangiopathies.