Anemia Due to Enlarged Blood Cells in Cats

PetMD Editorial
By PetMD Editorial on Jan. 6, 2009

Anemia, Megaloblastic (Anemia, Nuclear Maturation Defects) in Cats

In this disease, red blood cells fail to divide and become abnormally large. These cells are also deficient in necessary DNA material. These giant cells with underdeveloped nuclei are called megaloblasts, or "big cells." Red blood cells are mainly affected, but white blood cells and platelets can also go through changes.

For cats that have anemia associated with feline leukemia virus (FeLV), this type of anemia is expected to occur. The seriousness of the anemia can rang from mild to severe.

Symptoms and Types

  • Loss of appetite (anorexia)
  • Diarrhea
  • Pale skin color
  • Weakness
  • Sore mouth and tongue


  • Deficiencies of Vitamin B-12 and folic acid
  • Leukemia
  • Bone marrow disorder
  • Genetics
  • Drugs such as chemotherapy


Tests will be conducted to rule out the following:

  • All mild to moderate non-regenerative anemias, including those of inflammatory disease, renal disease, and lead poisoning
  • Complete blood counts will be taken and bone marrow aspiration analysis
  • In cats, the major disease to be ruled out is feline leukemia virus

Complete blood count, biochemistry, and urinalysis will examine the following:

  • Whether the anemia mild or moderate
  • Whether the anemia is caused by over-sized cells
  • In cats with feline leukemia: whether the anemia associated with a disorder of the spinal column or, possibly, with a different leukemia
  • Bone marrow biopsy usually reveals variable marrow findings

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Once the underlying cause is identified, a treatment plan will be developed to deal with that particular illness first. This is a relatively mild disease, except when it occurs in cats with the FeLV. Treatment will be administered on an outpatient basis. If your cat is demonstrating signs of drug toxicity, discontinue the offending drug. Instead, supplement your pet's diet with folic acid or vitamin B12.

Living and Management

Initially, you should take your cat in to see the veterinarian weekly for a complete blood count, and occasionally for a bone-marrow aspiration and evaluation. Cats that have the FeLV should be monitored carefully for a malformation of cells in the blood and bone marrow.

Ultimately, your cat's prognosis will depend on the underlying cause of the anemia. For example, cats that have anemia in conjunction with the FeLV will have an unfavorable prognosis. If a drug was the cause for the anemia, taking your cat off the drug should resolve the problem.

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