A novel acute lymphoid leukaemia type BCR/ABL transcript in chronic myelogenous leukaemia.

Using a reverse transcription-polymerase chain reaction (RT-PCR), we identified a patient with typical clinical features of chronic myelogenous leukaemia (CML) in the chronic phase who showed no amplification of the CML-type BCR/ABL transcript. RT-PCR with primers detecting the acute lymphoid leukaemia (ALL)-type transcript disclosed a novel fragment co-amplified with an ALL-type fragment. Sequencing revealed the novel transcript to be a chimaeric mRNA produced by fusion of a segment of BCR exon 2 (e2) to ABL exon 2 (a2), with a 21 base-pair insertion of ABL intron 1b sequence between them. This transcript has not been reported previously.