Parental origin and mechanism of formation of a 46,X,der(X)(pter→q21.1::p11.4→pter)/45,X karyotype in a woman with mild Turner syndrome

Objective

To describe the parental origin and the mechanism of formation of a 46,X,der(X)(pter→q21.1::p11.4→pter)[23]/45,X[8] karyotype in a patient with mild Turner syndrome.

Design

Case report.

Setting

A university hospital.

Patient(s)

A 23-year-old woman with normal height, gonadal dysgenesis, and mild Turner stigmata.

Intervention(s)

Genotype-phenotype correlation, array-based copy number analysis, fluorescence in situ hybridization with locus-specific probes, and microsatellite marker–mediated haplotype analysis subsequent to whole genome amplification of microdissected chromosomes.

Main Outcome Measures

Genotype-phenotype correlation, mechanism of formation, and parental origin.

Result(s)

Formation in paternal meiosis by refolding in itself and unequal recombination between Xp and Xq were found as the most likely mechanism of formation.

Conclusion(s)

Formation of der(X) chromosomes in females can be more complex than previously thought. The nearly normal height of this patient could be explained by a combination of trisomy of the Xp-located SHOX gene and mosaicism with a 45,X cell line.

Key Words: X chromosome, parental origin, translocation, Turner syndrome