CHARACTERIZATION BY CHROMOSOME PAINTING OF BALANCED AND UNBALANCED X-CHROMOSOME TRANSLOCATIONS IN MYELODYSPLASTIC SYNDROMES

Structural anomalies of the X chromosome, especially translocations, a re rare events in myelodysplastic syndromes (MDS). In a series of 2270 MDS patients analyzed between 1983 and 1994 (Center for Human Genetic s, Leuven), 9 cases were found with translocations involving the X chr omosome. These aberrations were not restricted to specific FAB subtype s and were the sole anomalies in 3 cases. In the remaining 6 patients, they were associated with other abnormalities, including 5q-, observe d in three cases. Fluorescence in situ hybridization (FISH) was retros pectively performed on 8 patients and was shown to be a useful complem ent for the characterization of the translocations involving the X chr omosome. In 3 cases, we could identify translocation partners and brea kpoint regions only by using chromosome pointing. No recurrent chromos ome partners were observed. The breakpoints could be localized along t he whole X chromosome. There was, however, a cluster in the Xq13 regio n involved in 4 of the 9 patients. The previously reported association of Xq13 anomalies with refractory anemia with ringed sideroblasts (RA RS) was found in only one case. Despite the lack of characteristic tra nslocations involving the X chromosome, the occurrence of such changes as the sole karyotypic anomaly suggests that they could play a role i n the pathogenesis of some myelodysplastic syndromes.