Aplastic pancytopenia

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Bone marrow smears of a dog with aplastic anemia (A) versus a normal dog (B). Note the absence of hematopoietic cells in A compared with normal bone marrow, in which hematopoietic precursor cells are abundant[1]

Aplastic pancytopenia (aplastic anemia) is a rare immune-mediated myelodysplastic syndrome of dogs characterized by anemia and adipose infiltration of bone marrow.

The disease is characterized by pancytopenia (reduced red and white cell numbers) in peripheral blood, associated with bone marrow hypocellularity[2].

Of cases reported in the literature, a number of etiological agents have been identified, including:

Clinically affected dogs are often young, but in cases where an underlying etiology is established, dogs can be of any age. General symptoms are often vague, including lethargy, fever (if secondary bacterial infection is present), weight loss and occasional vomiting.

Diagnosis is usually one of exclusion. Serology for Ehrlichia canis, antinuclear antibodies and fecal ELISA for parvovirus antigen are strongly recommended.

Imaging by MRI and bone marrow histological examination are usually required for establisshing a definitive diagnosis[9]. In young dogs, most of the marrow is active red marrow composed of precursors for red cells, white cells, and platelets. In adult dogs, there is a change to inactive yellow marrow that is predominantly composed of fat[10].

Treatment primarily aims at immunosuppressive therapy with high-dose prednisolone and azathioprine (2 mg/kg orally twice daily) or cyclosporine (5 mg/kg orally twice daily). Fortnightly blood transfusions may be required if PCV < 15.

The use of broad-spectrum antimicrobials is recommended if a secondary bacterial infection is suspected.

Although the prognosis is guarded, some dogs with aplastic pancytopenia recover.

References

  1. Kim JH et al (2012) Clinical and magnetic resonance imaging (MRI) findings of idiopathic aplastic pancytopenia in a dog treated with cyclosporine and azathioprine. Can Vet J 53(4):419-422
  2. Weiss DJ et al (1999) A retrospective study of canine pancytopenia. Vet Clin Pathol 28:83–88
  3. Weiss DJ (2000) Aplastic anemia. In: Feldman BF, Zinkl JG, Jain NC, editors. Schalm’s Veterinary Hematology. 5th ed. Philadelphia, Pennsylvania: Lippincott Wiliams & Wilkins. pp:212–215
  4. Brazzell JL & Weiss DJ (2006) A retrospective study of aplastic pancytopenia in the dog: 9 cases (1996-2003). Vet Clin Pathol 35(4):413-417
  5. Mylonakis, ME et al (2006) Diagnostic approach of canine pancytopenia. J Hellenic Vet Med Soc 57(1):69-77
  6. Weiss DJ & Klausner JS (1990) Drug-associated aplastic anemia in dogs: Eight cases (1984–1988). J Am Vet Med Assoc 196:472–475
  7. Weiss DJ (2003) New insights into the physiology and treatment of acquired myelodysplastic syndromes and aplastic pancytopenia. Vet Clin North Am Small Anim Pract 33:1317–1334
  8. Weiss DJ & Christopher MM (1985) Idiopathic aplastic anemia in a dog. Vet Clin Pathol 14:23–25
  9. Vande Berg BC et al (1998) Magnetic resonance imaging of the normal bone marrow. Skeletal Radiol 27:471–483
  10. Armbrust LJ et al (2008) Magnetic resonance imaging of bone marrow in the pelvis and femur of young dogs. Vet Radiol Ultrasound 49:432–437