Erythrocytosis and marked leukocytosis in overlapping myeloproliferative diseases

Chronic myelogenous leukemia (CML) and polycythemia vera (PV) are included in the spectrum of diseases referred to as myeloproliferative disorders. Patients with CML are frequently anemic at the time of diagnosis. Occasionally, however, erythrocytosis may be present in patients with CML, suggesting a diagnosis of PV. Mild neutrophilic leukocytosis is frequent in PV but marked leukocytosis is uncommon. We describe two patients with erythrocytosis and marked leukocytosis subsequently classified as CML and PV by the use of leukocyte alkaline phosphatase (LAP) scores and cytogenetic studies to detect the Philadelphia (Ph¹) chromosome.