[Development of Ph negative acute myeloid leukemia in a patient with minor-BCR/ABL positive chronic myeloid leukemia achieving a partial cytogenetic response during tyrosine kinase inhibitor treatment].

A 78-year-old male, who had CKD and chronic heart failure, was referred to our hospital for evaluation of leukocytosis. His bone marrow contained 12% blast cells and chromosome analysis showed the Ph chromosome as well as other changes. The patient was diagnosed with the accelerated-phase CML because FISH and RT-PCR disclosed BCR/ABL fusion signals and minor BCR/ABL, respectively. Imatinib was administered, but the CML was resistant to this treatment. We gave him nilotinib employing a reduced and intermittent administration protocol because of the progression of anemia and heart failure. The patient achieved PCyR in 8 months, but, 12 months later, his WBC count increased and 83% of the cells were blasts. Because the probable diagnosis was the blast crisis of CML, we switched from nilotinib to dasatinib. However, leukocytosis worsened and he died of pneumonia. It was later revealed that he had a normal karyotype and both FISH and RT-PCR analysis of BCR/ABL were negative. His final diagnosis was Ph negative AML developing from Ph positive CML in PCyR. Since there were no dysplastic changes indicative of MDS, it was assumed that the AML was not secondary leukemia caused by the tyrosine kinase inhibitor but, rather, de novo AML.