Silent Philadelphia chromosome: A distinct developmental stage in a Philadelphia chromosome-positive chronic myeloproliferation?

In this paper, a patient is described rt ilo presented with peripheral bloo d and bone marrow features uncharacteristic of chronic granulocytic leukemi a, which proved to be Philadelphia (Ph) chromosome-positive by metaphase an d interphase cytogenetic analyses but lacked the p210 type of BCR/ABL fusio n gene mRNA product by two different sensitive RT-PCR assays. In the course of the 32-month follow-up, with a termination into a myeloblastic crisis, molecular investigations were performed four times. They indicated a consta ntly high rate of Ph positive cells and lack of BCR/ABL mRNA expression, ex cept in the second investigation, when the patient showed reverse transcrip tion polymerase chain reaction positivity with b3/a2 type of chimera, fusio n gene mRNA expression, and a striking change in the bone marrow histology. Our findings might indicate that the dormant Ph chromosome state may exist not only at the primitive progenitor, but also at the entire peripheral bl ood cell compartment level. (C) Elsevier Science Inc., 2000. All rights res erved.