We present a 46-year-old patient with Ph-chromosome negative, bcr-negative
chronic myeloid leukaemia (CML) in accelerated phase with a clonal trisomy
21 in the leukaemic blast cells. A rapid progress of disease with appearanc
e of monocytosis is described, showing similar features to chronic myelomon
ocytic leukaemia (CMML), Heterogeneous characteristics and possible distinc
tion of these two entities are discussed.