Felis ISSN 2398-2950

Myeloid leukemia

Synonym(s): Myeloproliferative disease, AML, GML

Contributor(s): Jo Morris


  • Cause: arises from neoplastic transformation and proliferation of early myeloid precursor cells.
  • Aggressive and rapidly progressive disease of unknown etiology.
  • More common in cat (10% of hemopoietic neoplasia) than other domestic species but still rare.
  • Most cases are FeLV positive.
  • Signs: non-specific and due to consequences of abnormal marrow function, ie anemia, thrombocytopenia, neutropenia.
  • Diagnosis: by recognition of neoplastic cells in peripheral blood and in bone marrow - may require cytochemical stains to distinguish different neoplastic cell types.
  • Treatment: supportive and specific cytotoxic drugs.
  • Prognosis: very poor for acute forms, good for chronic disease.



  • Unknown.



  • Replacement of bone marrow with neoplastic cells   →   anemia, thrombocytopenia, neutropenia   →   lethargy, bleeding, susceptibility to overwhelming sepsis.
  • Infiltration of other organs with neoplastic cells   →   neurological signs, bone pain, organ dysfunction.
  • Increased numbers of circulating neoplastic cells   →   hyperviscosity.
  • May go on to develop myelofibrosis.
  • A number of different classification systems for myeloproliferative diseases exist.
  • Classifying according to cell lineage and chronicity is useful clinically:
  • Acute:
    • Undifferentiated.
    • Myeloblastic.
    • Myelo monocytic.
    • Erythroleukemia.
    • Megakaryocytic
  • Chronic:
    • Chronic myeloid leukemia.
    • Polycythemia vera.
    • Essential thrombocythemia.


  • Defined as prominent dysplastic changes in 1 or more of erythroid, myeloid or megakaryocytic lines but <30% of blast cells in bone marrow.
  • Myelodysplasia and chronic forms may transform to acute blastic crises.

Granulocytic series

  • Most common form.
  • Acute myelogenous leukemia has a high number of myeloblasts in peripheral blood, bone marrow and spleen and a poor survival rate.
  • Chronic myelogenous leukemia is rare and difficult to differentiate from leukaemoid response. Basophilic leukemia must be differentiated from mast cell leukemia, and eosinophilic leukemia may form part of feline hypereosinophilic syndrome.

Monocytic series

  • Results in monocytosis with monoblasts and intermediately differentiated cells in circulation (occasionally myelomoncytic).

Erythroid series

  • Erythroleukemia is characterized by large numbers of nucleated erythroid cells in circulation with concurrent anemia.
  • Polycythemia rubra vera or primary polycythemia often presents with no clinical signs until PCV 0.70-0.90 l/l (survival times 2-3 years with treatment).

Megakaryocytic series

  • Megakaryocytic leukemia presents with large numbers of megakaryocytes in peripheral blood, bone marrow and spleen- platelet numbers vary.
  • Essential (primary) thrombocythemia is very rare, but predisposes to thromboemboli or hemorrhage.


  • Acute disease days to weeks.
  • Chronic forms may live for several years.


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Further Reading


Refereed papers

Other sources of information

  • Ward H and Couto C G Myeloid leukaemia. In: Consultations in feline internal medicine pp509-513.