BASICS
- Term used to describe concurrent decrease in circulating erythrocytes, leukocytes, and thrombocytes
- Rare in horses
- Usually associated with disrupted hematopoiesis due to either a failure of stem cells to undergo differentiation (aplastic anemia) or destruction of the bone marrow microenvironment by neoplastic, fibrous, or inflammatory diseases (myelophthisis)
- Clinical signs reflect inadequate numbers of functional cells in blood or tissues and are usually nonspecific—weight loss, lethargy, poor performance, and intermittent pyrexia
- Onset is often insidious
- Hemorrhage due to thrombocytopenia—petechiation, epistaxis, mucosal bleeding, blood in feces, or prolonged bleeding from wounds
- Mucous membrane pallor, tachycardia, and systolic heart murmur with marked anemia
- Secondary infections due to leukopenia
- Aplastic anemia may be congenital or acquired and can result from intrinsic stem cell failure or disruption of stem cell interactions in the bone marrow. It is often idiopathic, but is rarely associated with administration of drugs (e.g. phenylbutazone, chloramphenicol, estrogens, trimethoprim, or pyrimethamine) or secondary to infectious disease (e.g. EIA virus or Anaplasma phagocytophilum)
- Myelophthisis has been associated with myelofibrosis, myelodysplasia, myeloproliferative disorders, or lymphoproliferative disorders
DIAGNOSIS
TREATMENT
MEDICATIONS
FOLLOW-UP
MISCELLANEOUS