Myelomonocytic leukemia: Disorderly proliferation of all marrow cells

Abstract

Myelomonocytic leukemia, our preferred designation for leukemia involving two or more marrow cell lines, is currently the most common type of leukemia seen at the Mayo Clinic. In an attempt to clarify the clinical picture and natural course of this myeloproliferative disorder, 132 patients first seen between 1955 and 1959 were studied. The disease, which usually had its onset after 50 years of age, was preceded in 41 patients by a preleukemic phase of variable duration. At the onset of overt leukemia, predominant involvement was of the erythrocytic and megakaryocytic compartments; during this phase the hematologic findings often suggested vitamin B12 or folate deficiency. As the disease evolved, it resembled acute granulocytic or monocytic leukemia or a mixture of these. The course, which was variable and unpredictable, ranged from a few weeks to several years.