A Ph+ acute myeloid leukaemia expressing both CML-type and ALL-type BCR/ABL mRNA transcripts.
This report describes a patient presenting with acute myeloid leukaemia (AML-FAB classification M2). Phenotypic markers were positive for cells of the myeloid lineage, but negative for monocyte/macrophage, megakaryocyte, and T-cell lineages. The occasional blast was positive for CALLA. All blasts carried the Philadelphia chromosome (Ph+), with 20% also harbouring a monosomy 7 (a cytogenetic marker for AML). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed the presence of two BCR/Abl mRNA transcripts; b2a2, the CML-type and E1a2, the ALL-type. Immunoglobulin (Ig) gene analysis demonstrated the presence of a small population of cells containing rearranged Ig genes. After a short remission, the patient relapsed. At relapse the leukaemia had undergone a major phenotypic switch from AML to ALL, with blasts bearing B-cell markers. Ig gene analysis confirmed a monoclonal population of B-cells. The Ph+ persisted, but the monosomy 7 had disappeared. The same two BCR/Abl mRNA transcripts were found at relapse as at presentation. To our knowledge, this is the first report of an AML simultaneously expressing BCR/Abl transcripts from both the minor and major BCR. The possible mechanisms of this dual expression are discussed.
Williams
B G
BG
Haematology Department, Royal North Shore Hospital, Sydney, New South Wales, Australia.
Yin
J L
JL
Ma
D D
DD
D001483:Base Sequence; D005260:Female; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D015870:Gene Expression; D015321:Gene Rearrangement; D016313:Genes, abl; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics*; D015470:Leukemia, Myeloid, Acute / Q000235:genetics*; D008875:Middle Aged; D008969:Molecular Sequence Data; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D014158:Transcription, Genetic
D012333:RNA, Messenger; D016044:Fusion Proteins, bcr-abl