Sequential development of chronic lymphocytic leukemia in a patient with polycythemia vera.

A patient with a seven-year history of polycythemia vera treated by repeated phlebotomies and intermittent busulfan administration developed gradually lymphocytosis accompanied by thrombocytopenia in peripheral blood and in the bone marrow. A marked pathological monoclonal proliferation of the B-cell population was detected. The sequential development of chronic lymphocytic leukemia in the patient with polycythemia vera could be considered as a coincidence because there is no reliable explanation of this event at present.