Anemia summary

The table below provides a summary of the mechanism and cause of anemia.

Causes of anemia
Type of anemia Causes
Hemorrhage Trauma, vessel wall injury or defects (e.g. vasculitis), hemostatic disorders (thrombocytopenia, von Willebrand disease, coagulation factor deficiency)
Inflammation (mostly ↓ production, mild hemolytic component) Many causes
Mechanisms: Cytokine suppression of erythropoiesis (erythropoietin release, responsiveness to erythropoietin), hepcidin-mediated sequestration of iron (decreased production), ↓ RBC life span (hemolytic)
Immune-mediated hemolytic anemia (hemolytic: extravascular or combination of intra- and extravascular) Idiopathic (most common)
Neoplasia (e.g. lymphoma)
Infections: Bacteria (e.g. Streptococcus equi, some hemotrophic Mycoplasma species), protozoa (e.g. Babesia), viral infections (e.g. equine infectious anemia)
Drugs (e.g. penicillin in horses)
Alloimmune: Neonatal isoerythrolysis, incompatible blood transfusion
Infectious agents (↓ production, hemolytic: extravascular or combination of intra- and extravascular) Erythroparasites: Mycoplasma, Babesia (can be intravascular hemolysis), Anaplasma, Cytauxzoon, Theileria spp (usually extravascular hemolysis; can be intravascular).
Trypanosomes: Trypanosoma cruzi (Chaga’s disease)
Viruses: Equine infectious anemia, Feline Leukemia Virus
Bacteria: Leptospira, Clostridia spp (can be intravascular hemolysis)
Oxidant injury (hemolytic: extravascular or combination of intra- and extravascular) Allium species or onion ingestion, acetaminophen toxicity (cats), zinc toxicity from pennies (dogs), red maple leaf toxicity (horses, camelids), Pistacia (a plant of the cashew family) toxicity (horses), copper poisoning (sheep), nitrate poisoning (cattle)
Fragmentation injury (↓ production, hemolytic: extravascular or combination of intra- and extravascular) Neoplasia (e.g. hemangiosarcoma), vascular disease (vasculitis), liver disease or disseminated intravascular coagulation
Defective hemoglobin synthesis (↓ production, hemolytic: extravascular or combination of intra- and extravascular) Dietary deficiency of iron (secondary to acidosis, excess vitamin C or zinc); copper deficiency (secondary to excess zinc)
Chronic external blood loss leading to iron deficiency: Gastrointestinal ulcers, blood-sucking gastrointestinal parasites (e.g. Haemonchus), vascular defects (e.g. colonic ecstasia), cancer; flea infestation; chronic urinary tract hemorrhage. Most common cause of iron deficiency in adult animals is chronic external gastrointestinal blood loss.
Chronic lead poisoning, inherited hemoglobinopathies (not naturally occurring in animals)
Histiocytic disorders Neoplasia (e.g. histocytic sarcoma), reactive histiocytic syndromes leading to erythrophagocytosis
Inherited RBC defects Membrane abnormalities: Hereditary stomatocytosis (Alaskan Malamutes, Miniature and Standard Schnauzers, Japanese black cattle); hereditary elliptocytosis: Spectrin deficieny (Golden Retriever)
Enzyme abnormalities in ATP generation pathway: Pyruvate kinase deficiency (Abyssinian and Somali cats, Beagles, Cairn Terriers, West Highland White Terriers and Basenjis), phosphofructokinase deficiency (e.g. English Springer Spaniels, American Cocker Spaniels)
Enzyme abnormalities in oxidant protection: Glucose-6-phosphate dehydrogenase deficiency (American Standardbred); flavin adenine dinucleotide (FAD) deficiency (Mustang)
DNA maturation abnormalities: Congenital dyserythropoietic anemia (Poll Hereford)
Uncharacterized defects (Shetland Sheepdog, Beagles, Abyssinian and Somali cats)
Drugs Immune-mediated: Penicillin (horses; extravascular hemolysis), human recombinant erythropoeitin (dogs, cats and horses; RBC progenitors leading to pure red cell a plasia), DMSO (horses; hemolytic)
Suppression/destruction of erythropoeisis: Chemotherapeutic agents, estrogen
Miscellaneous Hypophosphatemia (intravascular and extravascular hemolysis), e.g. phosphate-depleted dogs and cats with diabetes mellitus administered insulin, post-parturient hemoglobinuria in cattle (dietary deficiency); acute liver failure (equine; intravascular and extravascular hemolysis)
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