[Clinical features of a new category, myelodysplastic/myeloproliferative diseases, defined by WHO classification].

The WHO classification published in 2001 defined a new category of hematological disease, myelodysplastic/myeloproliferative diseases (MDS/MPD), that have both myelodysplasia and myeloproliferation at the time of initial presentation. This category consists of four subclasses, chronic myelomonocytic leukemia (CMML), atypical CML(aCML), juvenile chronic myelogenous leukemia and MDS/MPD-unclassifiable (MDS/MPD-u). In order to clarify the clinical features of these diseases, we analyzed clinical data of tentatively diagnosed MDS/MPD cases in the past ten years accumulated from affiliated hospitals. By reviewing the data of each case according to the criteria, we diagnosed 31 cases of MDS/MPD, including 22 cases of CMML, 5 cases of aCML and 4 cases of MDS/MPD-u. Male predominance and high age were common among these three subclasses. The prognosis of CMML was poor compared to other subclasses because of the high incidence of blast crisis. It is noteworthy that blast crisis in CMML exclusively occurred within one year after diagnosis. Young age, a high percentage of blasts in the peripheral blood, splenomegaly, lymphadenopathy and clonal cytogenetic abnormality were associated with blast crisis. It is suggested that there are two subgroups in CMML which differ in disease progression. Thus, these indicators may be useful in deciding the therapeutic strategy including hematopoietic cell transplantation for the high risk subgroup. There were four MDS/MPD cases with a history of preceding hematological diseases, such as aplastic anemia, MDS or malignant lymphoma. Among these, three cases with a long-term history of treatment with metenolone acetate developed CMML. It is suggested that the long-term effect of androgen plays a role in the pathophysiology of CMML.