[Unclassified chronic myeloproliferative disorder (Ph negative/bcr rearrangement negative CML) with late appearing Philadelphia like chromosome].

A 48-year-old male was diagnosed to be unclassified chronic myeloproliferative disorder (UCMPD)/Ph negative bcr rearrangement negative (Ph-/bcr-) CML by hematological, cytogenetical and DNA analyses (Jpn. J. Clin. Hematol. 33(4): 525-531, 1992). Three years and a half after the diagnosis of UCMPD/Ph-bcr- CML, Ph chromosome was observed in 17 of 20 examined cells. Hematological findings showed a transformation into blast crisis. The late appearing of Ph in a case of UCMPD/Ph1-bcr- CML described here is rare. Southern blot analysis using 3' and 5' bcr probe showed no bcr rearrangement. Analyses of BCR/ABL chimeric RNA by RT-PCR method were negative in both of Major- and Minor BCR/ABL chimeric RNA. In the present case it is speculated that Ph is developed as the result of multistep progression and also speculated that the breakpoint at BCR gene differs from Major- and Minor-bcr in usual Ph+CML and de nove Ph+ ALL. Therefore, it may be reasonable that the present case is understood to be a case with late appearing Ph-like chromosome.