Pediatric case of secondary leukemia associated with t(16;21)(q24;q22) exhibiting the chimeric AML1-MTG16 gene

A chimeric gene, AML1-MTG16, showing high homology to AML1-MTG8, was recently identified in adult leukemic patients with the abnormal karyotype t(16;21)(q24;q22). We recently saw a child patient of 11 years of age who developed acute myelogenous leukemia with the karyotype t(I 6;2 l)(q24;q22), 11 months after autologous peripheral blood stem-cell transplantation (PBSCT) for acute promyelocytic leukemia with karyotype t(15;17)(q22;q11). The reciprocal translocation was localized by fluorescence in situ hybridization (FISH) analysis, reverse transcription polymerase chain reaction (RT-PCR), and Southern blot analysis of bone marrow blood cells and peripheral blood cells. FISH analysis identified a reciprocal translocation between chromosomes 16 and 21. RT-PCR analysis identified expression of the chimeric gene AML1-MTG16. Southern blot analysis revealed a breakpoint occurring at a 1.4 kb Eco RI fragment between exons 3 and 4 of MTG16. The break-point is within the same region as that of secondary leukemias, which has been reported previously. This case suggests the possibility that the region of the breakpoint of MTG16 is a characteristic of secondary leukemia.