RBC morphology notecards Flashcards
(24 cards)
Anisocytosis
This can be due to increased numbers of large RBC or small RBC, or a combination of both. Some degree of anisocytosis is normal in animals.This is the smear equivalent of the red blood cell distribution width (RDW), which is a measure of the variation in RBC volume.
Acanthocytes
Mechanism: Alterations in lipid composition of RBC membrane and fragmentation. Physiologic: Young ruminants (calves). Disorders: ***Hemangiosarcoma (canine), liver disease (canine, feline), DIC (canine), vasculitis (canine), iron deficiency anemia (canine), possible congenital/inherited disorder (canine), various other diseases (e.g. renal, gastrointestinal, cardiac). Largest numbers observed in dogs with hemangiosarcoma.
Agglutination
Mechanism: Mediated by antibody bridging of adjacent RBC. Disorders: Immune-mediated hemolytic anemia (dog, cat, horse). Drugs: Heparin therapy (horses). Differentiate from: Rouleaux formation (does not usually disperse on saline dilution).
Basophilic stippled RBC
Mechanism: Aggregates of RNA due to RBC immaturity or Inhibition of RNA degradation. Does not require intravital dye precipitation to observe in a regularly stained blood smear (Romanowsky stain). Physiologic: Regenerative anemia (ruminants in particular, also dogs and cats but infrequent in the latter).m Pathologic: Lead poisoning (inhibits RNA degradation).
Dacryocytes
Disorders: Iron deficiency (camelids), myelofibrosis (dogs, not a consistent finding).
Drepanocytes
Mechanism: Specific types of hemoglobin form linear polymers under oxygenated states (frequently after blood sample collection). Normal in Deer, Antelope, sheep, mongoose, and genet.
Eccentrocytes
Mechanism: Oxidant-induced cross-linking of RBC membrane. Drugs: Vitamin K1, phenothiazine drenches (horse), new methylene blue, propofol, acetaminophen (cats). Disorders: Copper poisoning (sheep), red maple leaf toxicity (horses), onions (dogs, cats, cattle, horses), Brassica species, e.g. kale (ruminants), zinc toxicity (dog), naphthalene in mothballs (dog), skunk musk (dogs, panda), inherited defects (glucose-6-phosphate dehydrogenase deficiency, flavin adenine dinucleotide deficiency; both in horses), various diseases in dogs associated with oxidant injury (lymphoma, diabetes mellitus, anticoagulant rodenticide toxicosis).
Echinocytes
Mechanism: Expansion of the outer leaflet of RBC membrane, ATP depletion. Artifact: Stored (aged) blood, excess EDTA, increased pH. Drugs: Furosemide (horses), salicylates, phenylbutazone, doxorubicin (small animals). Disorders: Electrolyte depletion, glomerulonephritis, pyruvate kinase deficiency, snake envenomation (rattlesnake, coral snake, viper), burns, bee stings.
Elliptocytes
Three types: Type I (slightly oval), type II (oval), type III (elongate). Normal in camelids.
Ghost RBC
Mechanism: Rupture of RBC membrane, releasing hemoglobin and leaving membrane scaffolds. Artifact:In vitro hemolysis (poor sample collection, freezing of blood, aged RBC). Drugs: DMSO (horse). Diseases: Intravascular hemolytic anemia, due to immune-mediated hemolytic anemia in dogs, Babesia infection, copper poisoning in sheep, zinc toxicity in dogs, Clostridial toxins, hypophosphatemia, acute liver failure in horses, acute transfusion reaction, neonatal isoerythrolysis in horses, ruminants (not an exhaustive list).
Heinz bodies
Indicates oxidant injury. More readily visualized in a reticulocyte (new methylene blue) stain. Mechanism: Precipitated oxidized hemoglobin. Diseases: Oxidant injury (see eccentrocytes for diseases). The hemoglobin of cats is more susceptible to oxidant injury than other species, so low numbers of Heinz bodies are seen in the blood of non-anemic cats. In fact, some non-anemic cats can have many small refractile Heinz bodies due to endogenous (e.g. diabetes mellitus, hyperthyroidism, lymphoma) or exogenous oxidants (e.g. propylene glycol). These small Heinz bodies are called ?endogenous? Heinz bodies. In other species, Heinz bodies are associated with an oxidant-induced hemolytic anemia.
Hypochromic RBC
Mechanism: Decreased or inhibited hemoglobin production. Physiologic: Very young animals (physiologic iron deficiency anemia, easiest to identify in dogs). Mineral/nutrient deficiency: Iron deficiency (blood loss, nutritional deficiency), vitamin B6 deficiency (rare), copper deficiency (leads to iron deficiency), zinc excess. Diseases: Chronic external blood loss, chronic lead poisoning.
Keratocytes
Mechanism: Oxidant or fragmentation injury. Low numbers may be seen in non-anemic cats.
Macrocytes
Not synonymous with macrocytosis (high MCV). Low numbers of macrocytes may be seen without a high MCV (insufficient numbers to increase the MCV above the upper reference limit). Mechanism: Immature RBC (larger than normal), uptake of water, altered DNA metabolism. Artifact: Stored (aged) blood (may be associated with a low mean cell hemoglobin concentration), hyperosmolality (hypernatremia, hyperglycemia with the ADVIA hematology analyzer). Physiologic: Response to regenerative anemia (punctate reticulocytes). Mineral/nutrient deficiency: Vitamin B12 deficiency, folate deficiency, cobalt deficiency, molybdenum excess. Diseases: Feline leukemia virus infection (cats), congenital dyserythropoietic syndromes (poll Hereford), myelodysplastic syndrome, diabetes mellitus (RBC swelling), hyperthyroidism (unknown mechanism).
Microcytes
Difficult to identify true microcytes and RBC are not usually reported as microcytes in animals with MCV below the lower reference limit for that species. This term is rarely or not used at Cornell University, since it is of uncertain relevance and could encompass more diagnostic shapes, such as spherocytes, schistocytes. Identification of the latter specific shapes is more informative.
Poikilocytes
Mechanism: Various (see specific changes).
Polychromatophils
Mechanism: Immature RBC which contain abundant RNA (ribosomes, polyribosomes). Correspond to aggregate reticulocytes. Physiologic: Can be seen in normal dogs and cats in low numbers. Part of a regenerative response. Result reporting: Subjectively graded as mild, moderate, marked.
Punctate reticulocyte
Term used to identify immature RBC with small amounts of RNA that precipitate as small ?punctate? dots chunks when the blood is incubated with an intravital dye, such as new methylene blue. They are considered more mature than aggregate reticulocytes, because they contain less RNA. Punctate reticulocytes may be larger than normal and would correspond to macrocytes in a Romanowsky-stained blood smear (e.g. Wright?s, May-Grunwald-Giemsa, rapid stains). However, not all macrocytes are punctate reticulocytes (macrocytes can form through other mechanisms). Relevance: Included in a reticulocyte count in dogs, but not cats (can be counted separately from aggregate reticulocytes by certain laboratories; this is not done at Cornell University). Have a longer half-life in cats than aggregate reticulocytes (around 3 days) so do not indicate the current response by the bone marrow to an anemia. Only punctate reticulocytes may be released in mild anemias in cats.
Rouleaux formation
Mechanism: Decreased negative charge on RBC, usually due to increased globulins (fibrinogen, immunoglobulins). Physiologic: Horses, cats, pigs (can be normal in this species). Diseases: Inflammation (high fibrinogen, polyclonal gammopathy, restricted oligoclonal gammopathy), antigenic stimulation (polyclonal or restricted oligoclonal gammopathy), neoplasia of B cells (lymphoma, chronic lymphocytic leukemia) or plasma cells (multiple myeloma, extramedullary plasmacytome, solitary myeloma of bone) producing a monoclonal immunoglobulin. Should be associated with a high total protein by refractometer or high globulin on a chemistry panel. Differentiate from: Agglutination (three-dimensional clumps): Disperses with saline dilution (1:4 to 1:10 blood:saline)
Schistocytes
Mechanism: Shearing of RBC in the circulation due to abnormalities in the vasculature (endothelial cell, fibrin strands, blood flow) or mechanical RBC fragility (iron deficiency). Diseases: See above for acanthocytes. Also portosystemic shunts (altered blood flow).
Siderocytes
Mechanisms: Aggregates of iron (in lysosomes or mitochondria), due to increased iron turnover or inhibition of iron use. Drugs: Hydroxyzine, chloramphenical. Diseases: Hemolytic anemia (increased RBC turnover), myelodysplastic syndrome and acute myeloid leukemia (cats), lead poisoning, portosystemic shunts, vitamin B6 and copper deficiency in pigs.
Spherocytes
Mechanism: Removal of membrane by macrophages (trogocytosis). Artifact: Stored red blood cells (transfusions), feathered edge. Disease: Immune-mediated hemolytic anemia (primary or secondary to infectious agents, drugs), pyruvate kinase deficiency (spheroechinocytes), fragmentation (low numbers), hemophagocytic syndrome, histiocytic sarcoma, snake envenomation, inherited band 3 deficiency in Japanese black cattle.
Stomatocytes
Mechanism: Expansion of the inner leaflet of the RBC membrane. Artifact: Blood smear preparation. Physiologic: Woodchuck, manatee, dolphin. Disorders: Hereditary stomatocytosis in dogs (Alaskan Malamute, Drentje patrishond, standard and miniature Schnauzer, Peek-a-poo, Pomeranian).
Target cell
Only recognized in dogs, which have central pallor. Mechanism: Expansion of the inner leaflet of the RBC membrane, cells that spread in a smear than normal (leptocytes). Diseases: Iron deficiency anemia (hypochromic RBC), liver disease, lipid abnormalities.
