Acquisition of a Philadelphia chromosome concomitant with transformation of a refractory anemia into an acute leukemia.

The authors present a case of Philadelphia (Ph1) positive acute myeloblastic leukemia (AML) following a refractory anemia with excess of blasts (RAEB) that had been Ph1-negative for 17 months. During the transformation of RAEB into AML, the Ph1 was discovered in 100% of the examined cells. With therapy a partial remission was obtained, during which some 46,XY cells reappeared mixed with Ph1 cells along with a new clone: 47,XY,+11 originating from a Ph1-negative cell. During the terminal blast crisis, the karyotype returned to 46,XY,Ph1. The AML lasted 21 months. The authors discuss: (1) the significance of Ph1-positive AML with a review of the literature; (2) the de novo acquisition of a Ph1 during the course of a blood disorder; and (3) the meaning of a second abnormal clone originating from 46,XY cells.