The preleukemic syndrome.

While the preleukemic syndrome (PLS) is not a homogeneous entity, its spectrum of clinical and laboratory findings has been sufficiently characterized to allow increasing certainty in its recognition. Approximately 25 percent of these patients can be expected to develop overt acute nonlymphocytic leukemia (ANLL) within an average of two to three years, and another 40 percent will die of non-leukemic complications usually related to their cytopenias within a similar time period. The remaining patients may be stable and survive for prolonged periods. Accumulating evidence indicates that in the PLS, a stem cell neoplastic clonal proliferation has already been established and may frequently be demonstrated by cytogenic analysis or culture of marrow hematopoietic cells.