We reported three cases of myelodysplastic/myeloproliferatie diseases (MDS/MPD) which are Philadelphia (Ph) chromosome negative. The two patients had marked leukocytosis with various maturational stages of granulocytes with dysplasia. Philadelphia chromosome and BCR/ABL chimeric m-RNA were negative in these patients. We diagnosed as atypical chronic myeloid leukemia (aCML) for these patients. They were treated with a single agent and the combination chemotherapy, such as interferon (IFN) -α, and hydroxyurea (HU). However, these therapies were ineffective and these patients died of cerebral hemorrhage. The third patient was initially diagnosed with MDS with myelofiblosis. Later it transformed to chronic myelomonocytic leukemia (CMML) with increasing monocytes. The patient was treated with combination chemotherapy and VP-16. However, these therapies were ineffctive and the patient died of fungal infection of the respiratory tract.
The classification of these chronic myeloproliferative disorders waits for discussion, since the molecular pathogenesis of each disese has remained unsolved except for typical Philadelphia chromosome positive chronic myelogenous leukemia (CML).
The progress of studies for these myeloproliferative disorders, and the development of the effective treatment modalities including the specifically targeting therapy for the molecular abnormalities, are expected.

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