Myeloproliferative disorders.

Myeloproliferative disorders are uncommon in the dog and may be classified as chronic or acute. Excessive proliferation of mature cells leads to an overproduction of terminally differentiated blood cells (chronic MPD). Inability of cells to mature results in the accumulation of poorly differentiated blast cells in the peripheral blood and bone marrow (acute MPD). Because the lesion appears to be at the level of the hematopoietic stem cell, all cell lines in the bone marrow may be affected. Diagnosis depends upon the accurate identification of neoplastic cells and the absence of other diseases associated with bone marrow hyperplasia. The prognosis for chronic MPD is guarded, whereas for acute MPD it is grave. Accurate identification of these disorders in animals is important. Investigation and greater understanding of the pathophysiologic mechanisms may lead to more lasting therapeutic successes in the future.