[Chronic myelomonocytic leukemia transformed from refractory anemia with ring sideroblasts with a rare abnormal chromosome, inv (12)].

We report here a rare transformation from refractory anemia with ring sideroblasts (RARS) to chronic myelomonocytic leukemia (CMML). A rare karyotype, inv (12), was also seen at the phase of CMML. A 76-year-old female consulted a physician because of hoarseness in June, 1983. An anemia was found and blood transfusions were made. In August, 1983, she was referred and admitted to Tsukuba University Hospital for a further examination of anemia. A diagnosis of MDS (RARS) was made by hematological examinations, and pyridoxamine was administered from September, 1983. The monocyte counts in the peripheral blood increased above 1,000/microliters continuously from June, 1985, and an exacerbation of anemia was also seen. At the second admission to our hospital in August, 1988, the diagnostic criteria for CMML by the FAB co-operative group was fulfilled. At that time, chromosomal analysis revealed an abnormal karyotype; 46XY, inv (12) (p13.3 q15). Even at the phase of CMML, ringed sideroblasts were also seen in 2.2% of nucleated cell count in the bone marrow. To our knowledge, only 12 cases have been reported as transformation from another type of MDS to CMML. The present case is thought to be a rare case of transformation of MDS. On the other hand, 8 cases with inv (12) associated with malignant hematological disorders have been reported previously. Four of the above 8 cases were MDS. A relationship between development of MDS and inv (12) was suggested.