Paternally derived der(7)t(Y;7)(p11.1∼11.2;p22.3)dn in a mosaic case with Turner syndrome

An unusual mosaic karyotype was detected in a 6-year-old female patient with clinical diagnosis of Turner syndrome (TS). Cytogenetic and molecular cytogenetic studies revealed besides a cell line with 45,X a second cell line where the short arm of the Y-chromosome was translocated onto the short arm of a chromosome 7; karyotype: 45,X,der(7)t(Y;7)(p11.1∼11.2;p22.3)/45,X. To delineate the mechanisms of rearrangement and karyotypic evolution in this case, further studies were performed. A maternal origin of the X-chromosome and biparental origin of both chromosomes 7 were determined by microsatellite analysis. Furthermore, using parental-origin-determination fluorescence in situ hybridization (pod-FISH) it could be established that the derivative chromosome 7 was of paternal origin. Overall, this is to the best of our knowledge the first report of such a complex mosaic TS karyotype.