[Exacerbation of acute leukemia bearing isolated i(17q) along with proliferation of blasts with high BMI-1 expression].

We report a case of acute leukemia with an isolated isochromosome 17q karyotypic abnormality, which may be transformed from myeloproliferative disease (MPD)/myelodysplastic syndrome (MDS). A 69-year-old male patient with 27% of blasts in the peripheral blood underwent hematological examinations including cytochemical staining of cells such as myeloperoxydase (MPO), surface marker study on blasts, chromosomal test and bcr-abl mRNA analysis. The cytological and molecular findings (MPO-positive, myeloid marker CD13 expression (67.3%) and megakaryocytic marker CD41 expression (24.8%)) indicated that the blasts were consistent with myeloid leukemic cells partially committed to megakaryocytes. He was diagnosed as having leukemic transformation from MPD/MDS based on history of leukocytosis and thrombocytosis, isolated i(17q), bcr-abl negative, hepatosplenomegaly, increased eosinophil/basophil count and cytologic dysplasia. Positivity of BMI-1 in CD34+ blasts was 25.8% at the diagnosis and anti-leukemic drugs including anthracyclines were effective for his disease control during 6 months. However, the CD34+ cells turned out to highly express BMI-1 (83.1%), and leukemic cells started to increase progressively following which the leukemic cells failed to respond efficiently to any anti-leukemic drugs. Thus, expression of BMI-1 was well correlated with the disease progression, growth ability of blasts and resistance to anti-cancer drugs, indicating that BMI-1 positivity in CD34+blasts is an excellent molecular marker for disease progression and prognosis in such patients.