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

T HE ASSOCIATION of a variety of chromosome abnormalities with human leukemias has been well established. The discovery of the Philadelphia chromosome is of particular significance because it is the first instance in which there is an association of a specific chromosome abnormality with a particular type of leukemia. The Philadelphia ( Ph1 ) chromosome is present in the marrow of most patients with chronic myelogenous leukemia, but has not been found in conditions resembling chronic myelogenous leukemia such as leukemoid reactions, polycythemia vera, agnogenic myeloid metaplasia or myelofibrosis. 5 It has been presumed that the Pht chromosome occurs uniquely in leukemic cells, since it has not been found in cultured skin from patients with chronic myelogenous leukemia.4 Two recent preliminary reports suggest, however, that it may occur in erythroid precursors and megakaryocytes of such patients.5-7 The present report confirms and extends these findings.