[Partial and complete disappearance of Ph1 chromosome in two patients with chronic myelogenous leukemia after conventional chemotherapy].

[Case 1] A 44-year-old female was referred to our hospital because of leukocytosis. The WBC count was 26400/microliters and NAP score 21. As Ph1 chromosome was detected, she was diagnosed as CML and treated with busulfan. Because of the rapid decrease of WBC, we stopped busulfan. Progressive pancytopenia and an increase of myeloblasts and promyeloblasts in the bone marrow was observed. We started vincristine and prednisolone therapy. Ph1 chromosome was not detectable and southern blot analysis did not show rearranged bands of M-bcr three years after the last therapy. [Case 2] A 74-year-old female was referred to our hospital by reason of leukocytosis and thrombocytosis. The WBC count was 22,500/microliters, the platelet 907,000/microliters, NAP score 53, and Ph1 chromosome was found. The diagnosis of CML was made, and she was treated with busulfan. The WBC rapidly fell to 1,900/microliters, when chromosome analysis revealed the presence of Ph1 negative clones (4/20). She was admitted due to thrombocytopenia and leukocytosis with the additional chromosome change of i (17q). Her peripheral blood and bone marrow pictures were consistent with blast crisis, and she died of cardiac tamponade. These two cases show the heterogeneity of CML patients, and also suggest the possibility that keeping the WBC count low may lead to a decrease of Ph1 positive clones.