Highly complex genetic rearrangement involving at least seven breakpoints in a case of chronic myeloid leukemia.
Cytogenetic analysis for an atypical case of chronic myeloid leukemia (CML) showed a complex karyotype with four chromosome breakpoints (5q12, 12q21, 12q24, and 22q11) and translocation products that included a typical Philadelphia chromosome but apparently normal chromosomes 9. Molecular genetic analyses using four breakpoint cluster region (bcr) probes indicated that three breaks were probably present on chromosome 22. Two apparently independent breaks appeared to exist within the bcr, one of which was probably associated with a deletion of some bcr sequences. By combining the molecular and cytogenetic data, we could infer a total of seven breaks. This case illustrates the extensive and complex types of genetic alteration that may be associated with a c-abl and bcr fusion.