[Acute myelocytic leukemia with ins(21;8)(q22;q13q22) presenting with AML1/MTG8 chimeric mRNA].

We report a case of acute myelocytic leukemia (AML) showing a chromosomal abnormality, ins(21;8), with AML1/MTG8 chimeric mRNA. The patient, a 73-year-old woman, was admitted to our hospital because of AML relapse. Bone marrow aspiration showed 44% blasts and ins(21;8)(q12;q13q22) by cytogenetic study. Moreover, the size of chimeric AML1/MTG8 mRNA detected by RT-PCR in this case was shorter than that of previously reported. The patient was diagnosed as having relapse of AML (M2), but achieved complete remission with DCP therapy. Four months later, extramedullary relapse occurred, and this was followed five months later by bone marrow relapse. However, the patient again achieved complete remission. Most cases of AML1/MTG8 fusion gene are caused by t(8;21), and only very rarely by ins(21;8). In this case, the AML1/MTG8 fusion gene is thought to have been involved in the onset of leukemia.