[BCR rearrangement and cytogenetic findings in Philadelphia-positive chronic myelocytic leukemia in children].

Eight children with Philadelphia (Ph1) chromosome positive chronic myelocytic leukemia (CML) were available for cytogenetic studies and breakpoint cluster region (bcr) rearrangement analysis as compared to the features of adults with Ph1-positive CML. In chronic phase additional abnormalities other than Ph1 chromosome were found in none of our cases. On the other hand, in blastic crisis all of 6 cases had additional chromosomal abnormalities like as i(17q), double Ph1 and +8. The frequency of the appearance of additional chromosomal abnormalities, especially i(17q), is higher in children than in adult cases. In the DNA of 7 of 7 examined patients, rearrangement of bcr could be demonstrated by Southern blot analysis. These findings were similar to those observed in adults. An analysis of the location of the bcr breakpoint indicated that 5' breakpoints were found in four cases who were long-term survivors, and two of the other cases had blastic crisis from the onset of the disease. These findings showed the cytogenetic findings of children with Ph1+CML were different from those of the adult cases in the frequency of the appearance of the additional chromosomal abnormalities, and the location of the bcr breakpoint in children cases might be different from that in the adult cases and influence its prognosis.