[Identification and characterization of marker chromosome in Turner syndrome].

Objective: To analyze the karyotypes of 11 cases of Turner syndrome with marker chromosome, and study the phenotypic effects resulting from the abnormal karyotype.
Methods: Eleven Turner syndrome patients had a mosaic karyotype and carried a marker chromosome, and 6 marker chromosomes were ring chromosomes. Their karyotypes were showed as mos. 45, X/46, X, + mar or mos. 45, X/46, X, + r. Fluorescence in situ hybridization (FISH) technique with X/Y centromere probes was performed to determine the origin of the marker chromosome. Reverse chromosome painting technique was used to identify the breakpoints of two largest markers. Phenotype effects with different chromosome breakpoints were compared.
Results: All the 11 marker chromosomes were ring X chromosomes. The breakpoints of the r(X) were involved in Xp22, Xq22, Xq24 and Xq26, etc.
Conclusions: The marker chromosomes in Turner syndrome mainly originate from X chromosome and form ring chromosome X. Each r(X) in our patients was mosaic, indicating it was originated from mitosis error during early embryo development. To analyze the origin of the marker chromosome and the breakpoint of r(X) will provide guidance for the therapy and prognosis of the Turner syndrome patient.