Preleukemia: A Myelodysplastic Syndrome Often Terminating in Acute Leukemia

"Preleukemia" is a hematologic disorder frequently terminating in acute nonlymphoblastic leukemia in adults. The salient features of this syndrome include the following: (1) a decrease in the number of at least one cell line in the peripheral blood; (2) a hypercellular bone marrow with distinct abnormalities in both the erythroid and granulocytic cell lines; (3) an insidious onset, usually beginning after the age of 50 years; and (4) a high probability of termination in acute leukemia. There is evidence that preleukemia represents a myeloproliferative disorder. Review of the literature indicates that this disorder is variable in duration (2 to 108 months) and occurs frequently.