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Clinical and molecular cytogenetic characteristics of the unique pseudotricentric X chromosome

https://doi.org/10.25557/2073-7998.2023.08.44-51

Abstract

Structural and numerical rearrangements of the sex chromosomes represent the most commonly observed chromosomal abnormalities that are compatible with live birth. Compared to numerical or structural autosomal rearrangements abnormalities of sex chromosomes tend to have less pronounced clinical consequences. In women with phenotypic manifestations of Turner syndrome, structural anomalies of the X chromosome, particularly in the mosaic form, are frequently observed in the karyotype. However, in individuals with a structurally rearranged sex chromosome, developmental anomalies may be absent. This can be attributed to the absence of cell clone 45,X and selective inactivation of the rearranged X chromosome. The wide phenotypic variability and limited data available on patients with structural anomalies of the X chromosome significantly complicate the process of medical genetic counseling for such patients. In this report, we present a unique case of a pseudotricentric X chromosome featuring a short arm duplication, four copies of the Xq11.1q22 region, and a deletion of the Xq22 long arm terminal region. The aim of the study was to establish the structure and mechanism of the formation of an abnormal X chromosome in a patient with delayed psychomotor and sexual development. A standard cytogenetic study, FISH, chromosomal microarray analysis was carried out. The pseudotricentric X chromosome with a duplicated short arm, partial tetraplication, and a long arm deletion is a unique structural gonosomal rearrangement. An integrated molecular cytogenetic approach made it possible to determine the structure of the derivative X chromosome and establish the genotype-phenotype interaction in the presence of a pseudotricentric X chromosome in the genome.

About the Authors

Zh. G. Markova
Research Centre for Medical Genetics
Russian Federation

1, Moskvorechye st., Moscow, 115522



M. E. Minzhenkova
Research Centre for Medical Genetics
Russian Federation

1, Moskvorechye st., Moscow, 115522



F. M. Bostanova
Research Centre for Medical Genetics
Russian Federation

1, Moskvorechye st., Moscow, 115522



N. V. Shilova
Research Centre for Medical Genetics
Russian Federation

1, Moskvorechye st., Moscow, 115522



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Review

For citations:


Markova Zh.G., Minzhenkova M.E., Bostanova F.M., Shilova N.V. Clinical and molecular cytogenetic characteristics of the unique pseudotricentric X chromosome. Medical Genetics. 2023;22(8):44-51. (In Russ.) https://doi.org/10.25557/2073-7998.2023.08.44-51

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