Canis ISSN: 2398-2942

Chronic myeloid leukemia

Synonym(s): Chronic granulocytic leukemia, CGL, CML

Contributor(s): John Dunn

Introduction

  • Chronic leukemias are less common than acute.
  • Signs: depression, pyrexia, lymphadenopathy, splenomegaly, +/- hepatomegaly.
  • Diagnosis: hematology, bone marrow cytology (limited value).
  • Treatment: may be none required depending on severity, chemotherapeutic agents.
  • Prognosis: affected animals may go into remission and most live for >1 year from diagnosis.

Pathogenesis

Etiology

  • The myeloproliferative disorders include a number of inter-related dysplastic and neoplastic conditions that result from the clonal proliferation of non-lymphoid stem cells (pluripotent stem cells that give rise to erythrocytes, granulocytes, monocytes and megakaryocytes). Usually, but not always, one cell line predominates.
  • NB: CML shares many clinical and laboratory features with other chronic myeloproliferative disorders, eg essential thrombocythemia, polycythemia Polycythemia: primary Polycythemia: secondary and myelofibrosis Myelofibrosis with myeloid metaplasia (all quite rare).
  • Note also that eosinophilic and basophilic variants of CML have also been reported, especially in cats, although these are relatively rare.

Pathophysiology

  • Myeloproliferative disease results from abnormal proliferation of myeloid cell populations from a single pluripotent stem cell.
  • Leukemia implies that these neoplastic white blood cells are found in the peripheral blood but this is not necessarily the case (although this tends to be the case with CML - problem is neutrophils appear normal morphologically but white blood cell count usually raised).
  • The abnormal cells may not be released into the circulation and build up in the marrow in large numbers while the circulating cell counts remain normal. This is more a feature of acute leukemias in general.
  • As the marrow production of cells shifts towards the neoplastic cells other cell series may be affected → anemia or thrombocytopenia (although some cases may have thrombocytosis).
  • Initially cell maturation occurs in an orderly fashion but most cases progress towards an acute blastic crisis in which cell maturation ceases.
Pyrexia
  • Presumptively caused by one or a combination of:
    • Pyrogen production by neoplastic cells possible.
    • Increased metabolic rate due to high cell turnover.
    • Infection due to abnormal neutrophil function?

    Anemia

  • Due to reduced production of cells in marrow.

    Organomegaly

  • Of spleen, lymph nodes, +/- liver may be caused by a number of factors:
    • Infiltration of organ with neutrophils.
    • Extramedullary hematopoiesis.

Timecourse

  • Months to years.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Fine D M & Tvedten H W (1999) Chronic granulocytic leukemia in a dog. JAVMA 214 (12), 1809-1812 PubMed.
  • Dunn J K, Jefferies A R, Evans R J et al (1987) Chronic granulocytic leukaemia in a dog with associated bacterial endocarditis, thrombocytopenia and preretinal and retinal haemorrhage. JSAP 28 (11), 1079-1086 VetMedResource.
  • Evans R J & Gorman N T (1987) Myeloproliferative disease in the dog and cat - definition etiology and classification. Vet Rec 121 (19), 437-443 PubMed.
  • Gorman N T & Evans R J (1987) Myeloproliferative disease in the dog and cat - clinical presentation, diagnosis and treatment. Vet Rec 121 (21), 490-496 VetMedResource.


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