Objective: To identify the origin of marker chromosome of patients with Turner syndrome, and to provide the information for genetic counseling and treatment.
Methods: The karyotypes of 32 patients with Turner syndrome from 2001 to 2003 at the Center for Diagnosis of Genetic Metabolic Diseases were reviewed. Metaphase chromosome analyses of peripheral blood lymphocytes, G-band and C-band were performed using standard methods. Fluorescence in situ hybridization (FISH) was performed to identify the origin of marker chromosome by using two probes: sex-determining region Y (SRY) for band region Yp11.3 and chromosome enumeration probe for X(CEPX) for band region Xp11.1-q11.1.
Results: 3/32(9.4%) patients with Turner syndrome had marker chromosome, the karyotype being 45,X/46,X,mar. Among the 3 marker chromosomes, 2 originated from chromosome X or Y, as identified by the FISH. The origin of the third marker chromosome could not be identified by CEPX and SRY probes.
Conclusion: The presence of a marker chromosome in Turner syndrome generally implicates a sex chromosome origin. It may also originate from a non-sex chromosome. Therefore, it is necessary to apply X and Y probes simultaneously for marker chromosome detection in Turner patients with monosomy X.