Structural anomalies of the X chromosome, especially translocations, are rare 
events in myelodysplastic syndromes (MDS). In a series of 2270 MDS patients 
analyzed between 1983 and 1994 (Center for Human Genetics, Leuven), 9 cases were 
found with translocations involving the X chromosome. These aberrations were not 
restricted to specific FAB subtypes and were the sole anomalies in 3 cases. In 
the remaining 6 patients, they were associated with other abnormalities, 
including 5q-, observed in three cases. Fluorescence in situ hybridization 
(FISH) was retrospectively performed on 8 patients and was shown to be a useful 
complement for the characterization of the translocations involving the X 
chromosome. In 3 cases, we could identify translocation partners and breakpoint 
regions only by using chromosome painting. No recurrent chromosome partners were 
observed. The breakpoints could be localized along the whole X chromosome. There 
was, however, a cluster in the Xq13 region involved in 4 of the 9 patients. The 
previously reported association of Xq13 anomalies with refractory anemia with 
ringed sideroblasts (RARS) was found in only one case. Despite the lack of 
characteristic translocations involving the X chromosome, the occurrence of such 
changes as the sole karyotypic anomaly suggests that they could play a role in 
the pathogenesis of some myelodysplastic syndromes.