MLL gene rearrangement in t(9;11) acute myelogenous leukemia with minimal myeloid differentiation (FAB subtype M0).

A 25-year-old man was diagnosed with acute myelogenous leukemia (AML), French-American-British (FAB) subtype M0, based on cytochemical and flow cytometric findings. Cytogenetic analysis revealed the chromosome translocations t(9;11)(p22;q23), and MLL gene rearrangement was identified by Southern blotting. In adult AML, MLL gene rearrangement was initially reported in FAB M4 and M5 cases, and recently in Ml and M2 cases, but was rare in M0 or M3 cases. Because the sensitivity of detecting MLL gene rearrangement by cytogenetic analysis is extremely low compared with Southern blotting analysis, the MLL gene may be involved in substantial numbers of adult AML cases, regardless of FAB subtype.