Equis ISSN 2398-2977

Myeloproliferative disorders

Synonym(s): Myeloid neoplasia, myeloid leukemia

Contributor(s): Katherine Edgar, Prof Derek Knottenbelt, Anna Hollis

Introduction

  • See Bone marrow: disorders - overview.
  • Very rare.
  • No breed or sex predilection.
  • Has been reported in ages 10 months to 16 years.
  • Cause: acute or chronic malignant proliferation of myeloid cells.
  • Signs: non-specific clinical signs.
  • Diagnosis: clinical signs, hematology, bone marrow biopsy Bone marrow: biopsy.
  • Treatment: corticosteroids and chemotherapy protocols may be palliative. Timely euthanasia.
  • Prognosis: poor.

Pathogenesis

Pathophysiology

  • Unregulated proliferation of bone marrow derived myeloid cell lines crowds out or inhibits normal blood cell replication.
  • The primary reason for the expansion of the myeloid mass is the failure of the stem cells to respond to the normal feedback mechanism that limits the marrow cell density.
  • The increased myeloid cell mass is responsible for deficient neutrophil alkaline phosphatase, impaired phagocytic ability of neutrophils, and thrombocyte and erythrocyte abnormalities.
  • Myelofibrosis occurs as a reaction to the presence of the proliferating neoplastic clones.
  • Immunosuppression → secondary bacterial and fungal infections.
  • Extramedullary hemopoiesis occurs in the spleen causing splenomegaly.
  • Hemorrhagic diathesis is caused by thrombocytopenia.

Timecourse

  • A couple of months without treatment.
  • Corticosteroids and chemotherapy protocols may be useful for palliation of the disease.

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.
  • Henson F M D & Dobson J M (2004) Use of radiation therapy in the treatment of equine neoplasia. Equine Vet Educ 16 (6), 315-318 VetMedResource.
  • Beucher-Maxwell V, Zhang C, Robertson et al (1994) Intravascular leukostasis and systemic aspergillosis in a horse with subleukemic acute myelomonocytic leukemia. J Vet Intern Med 8, 258-263 PubMed.
  • Lester G D, Alleman A R, Raskin R E et al (1993) Malignant histiocytosis in an Arabian filly. Equine Vet J 25, 471-473 PubMed.
  • Bienzle D, Hughson S L & Vernau W (1993) Acute myelomonocytic leukemia in a horse. Can Vet J 34, 36-37 PubMed.
  • Blue J, Perdrizet J & Brown E (1987) Pulmonary aspergillosis in a horse with myelomonocytic leukemia. JAVMA 190 (12), 1562-1564 PubMed.
  • Morris D D, Bloom J C, Roby K A W et al (1984) Eosinophilic myeloproliferative disease in a horse. JAVMA 180, 313-316 PubMed.


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