The clinical analysis of small supernumerary marker chromosomes in 17 children with mos 45,X/46,X,+mar karyotype.

Small supernumerary maker chromosome (sSMC) is a type of structurally abnormal chromosome. In order to identify the origin, morphology and other characteristics of sSMCs in children with mos 45,X/46,X,+mar karyotype, 17 patients (16 females and 1 male) were analyzed. All patients underwent general physical examination, gonadal imaging and molecular cytogenetic analyses, including Giemsa banding, dual-color fluorescence in situ hybridization and detection of the sex-determining region Y gene by polymerase chain reaction. Cytogenetic analyses indicated sSMCs in 14/17 cases were derived from the X chromosome, of which 8 individuals presented with ring-shaped sSMCs and 6 with centric minute-shaped sSMCs. The remaining 3 cases were derived from the Y chromosome, and all presented with minute-shaped sSMCs. All female patients exhibited short stature, gonadal dysgenesis and other typical features of Turner syndrome. The male patient exhibited short stature, hypospadias and bilateral cryptorchidism. In conclusion, the majority of the sSMCs in patients with a mos 45,X/46,X,+mar karyotype were derived from the sex chromosomes. The molecular cytogenetic features of sSMCs may provide useful information for genetic counseling, prenatal diagnosis and individualized treatment.