MYELOPOIESIS AND MYELOPROLIFERATIVE DISORDERS

Myelopoiesis describes the derivation of nonlymphoid cells that includ e granulocytes, monocytes, erythrocytes, and platelets from a common h ematopoietic stem cell. Current concepts of hematopoiesis including st imulating and inhibitory growth factors are discussed. Disturbances of development in myeloid stem cells results in dysplastic and neoplasti c conditions termed myeloproliferative disorders. A recently devised c lassification scheme for these disorders in dogs and cats provides a u niform manner to categorize myelodysplastic syndrome, acute myeloid le ukemia, chronic myeloid leukemia, and their subtypes using cytomorphol ogic methods. Emphasis in this article is given to recent studies in w hich this classification method can be applied to improve one's unders tanding of the pathogenesis of canine and feline myeloproliferative di sorders.