A novel large-sized BCR-ABL transcript in a case of chronic myeloid leukaemia characterised by a favourable clinical course.

The reciprocal translocation t(9;22)(q34;q11) is detected in95 % of chronic myeloid leukaemia (CML) as well as in 20–30 % of adult [1] and 2–5 % of childhood acute lymphoblasticleukaemia [2]. It involves the breakpoint clusterregion (BCR) gene locus on chromosome 22. Apart fromthe two principal breakpoints (the major BCR, betweenexons e12 and e16, and the minor m-BCR, in the firstBCR intron) and the rare μ-BCR in exon e19, other breakpointsare seldom observed [3–5]. The correlation betweenBCR gene breakpoints and the CML phenotype remains adebatable issue. A few authors believe, however, that smallBCR-ABL transcripts might have a stronger kinase activitythan the large-sized ones, thus inducing more aggressiveCML [6].We describe here a novel large-sized BCR-ABL transcript,which was associated with a CML characterised bya favourable outcome.