Translocation of c-abl oncogene and PDGFB (c-sis) gene in a case of CML with 46,XY, t(22;22)

Megakaryocytic blast crisis in a chronic myeloid leukemia patient with a rare variant of Philadelphia rearrangement t(9;22;22) and a constitutional translocation t(3;7)

Megakaryocytic blast crisis occurs extremely rarely, accounting for <3% of cases of chronic myelogenous leukemia in blastic transformation. In chronic myeloid leukemia, a variant Philadelphia translocation is reported in 2-10% of cases. We report an unusual case of megakaryocytic blast crisis with the Philadelphia variant rearrangement t(9;22;22) and a constitutional translocation t(3;7). The breakpoint in the 22q13 region was involved in this translocation. The chromosome region 22q13 harbors MKL1 gene, which is engaged in a specific translocation associated with acute megakaryoblastic leukemia. Study of deregulation of these four genes could contribute to better understanding of the effects of the t(9;22;22) rearrangement in a megakaryocytic blast crisis.

Cytogenetic peculiarities in chronic myelogenous leukemia

Cytogenetic investigations were performed in 185 patients with chronic myelogenous leukemia (CML) at all stages of the disease; 166 patients were Ph positive-159 (95.8%) of these showing the standard Ph translocation, and 7 (4.2%) variant translocations-17 patients were Ph negative. In 2 patients the cytogenetic analysis was unsuccessful. Additional aberrations were found in 40 (24.1%) of the Ph-positive patients. Nine (52.9%) of the Ph-negative patients showed chromosome anomalies. Besides the well known nonrandom abnormalities (-7, +8, i(17q), +19, +Ph) we found a high frequency of clones with rare or not yet described structural rearrangements--in 14 cases (34.2%) of the Ph-positive patients and in 2 cases (20%) of the Ph-negative patients with other chromosome abnormalities. The clinical significance of these findings is discussed.