Newer Aspects of Preleukemic Disorders

Abstract

Preleukemic disorders are a controversial group of panmyelopathic disturbances that often precede the emergence of acute myeloblastic or myelomonocytic leukemia. In most instances, these preleukemic disorders are characterized by slowly developing myeloblastosis of the bone marrow. They include preleukemia, primary acquired panmyelopathy with myeloblastosis or smouldering acute leukemia, erythroleukemia, and subacute myelomonocytic leukemia. Sometimes, transitions between these various preleukemic disorders may be observed in a single individual. Abnormalities in cellular differentiation are expressed in cytochemical aberrations and in elaboration of colony forming units by marrow cells of patients with preleukemic disorders. Cytogenic and cellular kinetic abnormalities link preleukemic disorders closely to acute myeloblastic or myelomonocytic leukemia, although in many patients with preleukemic disorders, conversion to acute leukemia is not observed or perhaps not recognized. Understanding pathogenetic and pathophysiological aspects of preleukemic disorders may shed light on aspects of cellular proliferation and cellular differentiation in the acute leukemias.

Postleukemic dysmyelopoiesis

“…The granulocytic series can also show megaloblastic changes as well as nuclear hypolobulation. Megakaryocytic abnormalities include hyperplasia with nuclear hyper-and hypolobulation [4-201. Various terms have been applied to these dysrnyelopoietic processes including preleukemia [4][5][6][7][8][9][10][11][21][22][23][24][25][26][27][28][29][30][31][32][33], smoldering (oligoblastic) leukemia [4, 61, hemopoietic dysplasia [ 12,341, idiopathic refractory sideroblastic anemia [ 1,21, subacute rnyelomonocytic leukemia 14, 131, and dysrnyelopoietic (myelodysplastic) syndromes such as refractory anemia with excess blasts and chronic myelomonocytic leukemia [ 13-18, Although the frequency of leukemic conversion varies, these subclassifications of preleukemic dysmyelopoiesis show frequent morphologic and clinical overlap [9,11,12,14,17,27,29,[34][35][36]. Indeed, this entire group of disorders may represent a morphologic spectrum of a bone-marrow stem-cell defect which is associated with a variable rate of conversion to ANLL.…”