Spectral karyotyping (SKY) refinement of a complex karyotype with t(20;21)in a Ph-positive CML patient submitted to peripheral blood stem cell transplantation

A patient with a Ph-positive chronic myeloid leukaemia (CML) was submitted to allogeneic peripheral blood stem cell transplantation from an HLA-haploi dentical related donor 7 years after the diagnosis. Six months later, he sh owed a disease relapse while cytogenetic analysis displayed a complex karyo type, To characterise the chromosomal rearrangements spectral karyotype (SK Y) analysis was used, This redefined all chromosome rearrangements and reve aled a t(20;21)(q11;q22), FISH analysis with a specific probe for the AML1 gene disclosed disruption of this gene which was partially translocated on to the long arm of chromosome 20, It is likely that this rearrangement, unu sual for CML, was implicated in the disease evolution towards blastic crisi s (BC).