Inconsistency of Karyotyping and Array Comparative Genomic Hybridization (aCGH) in a Mosaic Turner Syndrome Case

Abstract

Purpose Turner syndrome is a sex chromosomal aberration where majority of the patients have 45,X karyotype, while several patients are mosaic involving 45,X/46,XX; 46,X,i(Xq); and other variants. Cytogenetic analysis, karyotyping, is considered to be the “gold standard” to detect numerical and structural chromosomal abnormalities. In the recent years, alternative approaches, such as array comparative genomic hybridization (aCGH), have been widely used in genetic analysis to detect numerical abnormalities as well as unbalanced structural rearrangements. In this study, we report the use of karyotyping as well as aCGH in detecting a possible Turner syndrome variant.
Methods An apparent 16-year-old female was clinically diagnosed as Turner syndrome with premature ovarian failure and short stature. The genetic diagnosis was performed for the patient and the parents by karyotyping analysis. aCGH was also performed for the patient.
Main Findings Cytogenetic analysis of the patient was performed showing variant Turner syndrome (46,X,i(X)(q10)[26]/46,X,del(X)(q11.2)[11]/45,X[8]/46,XX[5]). The patient's aCGH result revealed that she has a deletion of 57,252kb of Xp22.33-p11.21 region; arr[GRCh37] Xp22.33-p11.21 (310,932-57,563-078)X1. Both aCGH and fluorescence in situ hybridization (FISH) results suggested that short stature Homeobox-containing (SHOX) gene, which is located on Xp22.33, was deleted, though FISH result indicated that this was in a mosaic pattern.
Conclusion In the recent years, aCGH has become the preferred method in detecting numerical abnormalities and unbalanced chromosomal rearrangements. However, its use is hindered by its failure of detecting mosaicism, especially low-level partial mosaicism. Therefore, although the resolution of the aCGH is higher, the cytogenetic investigation is still the first in line to detect mosaicism.

Keywords

turner syndrome / mosaicism / partial mosaicism / aCGH / cytogenetics

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