The Distribution of the Philadelphia Chromosome in Patients with Chronic Myelogenous Leukemia

Thirteen patients with chronic myelogenous leukemia continued to havethe Ph¹ chromosomes in 90-100 per cent dividing marrow cells during drug-induced clinical remissions. The Ph¹ chromosome was present in erythroidas well as granulocytic marrow cells, and possibly in megakaryocytes.

The presence of Ph¹ chromosomes was also studied in cultures of peripheralblood. In six patients in relapse, 40 per cent of metaphases contained the Ph¹chromosome, and the percentage of these cells corresponded roughly to therelative frequency of immature granulocytes in the blood. In contrast, duringremission, few or no Ph¹ chromosomes were found in peripheral blood cultures, presumably because in the absence of immature granulocytes the dividing cells in the cultures originate from lymphocytes, as they do in normalblood.

It is suggested that the Ph¹ chromosome usually arises in a precursor cellcommon to the erythroid, granulocytic, and megakaryocytic, but not thelymphoid series of hemopoietic cells.

Submitted on April 5, 1963 Accepted on June 30, 1963