Atypical BCR-ABL fusion transcript (e6a2) in pediatric acute lymphoblastic leukemia

Abstract

Introduction: Among precursor-B-acute lymphoblastic leukemia cases, BCR-ABL translocation occurs in around 20-30% of adults and in ≤5% of children. Minor breakpoint transcripts (e1a2) are found in about 70% of positive BCR-ABL cases and major breakpoint transcripts (e13a2, e14a2) in about 30% cases. However, other atypical transcripts are sometimes observed. Case Report: A rare form of chimeric BCR-ABL fusion transcript (e6a2) was detected in a pediatric patient with precursor-B-acute lymphoblastic leukemia by reverse transcriptase polymerase chain reaction. Sequence analysis of the fusion region of the amplified cDNA fragment showed an in-frame joining of exon 6 of the BCR gene and exon 2 of the ABL gene, giving rise to an e6a2 BCR-ABL transcript. This finding was also confirmed by fluorescent in situ hybridization. Conclusion: The findings in this case shows that atypical BCR-ABL transcripts are detectable in acute lymphoblastic leukemia patients without M-BCR-rearrangements. Reverse transcriptase polymerase chain reaction using primers that allow for amplification of all known BCR-ABL transcripts is an appropriate method to detect these rare variants.