Genetic analysis of Turner syndrome in Tunisian patients: from diagnosis to management

Abstract

Background/aim Turner syndrome (TS) is a rare sex chromosome abnormality in women, occurring in approximately one in 2500 live births, associated with a wide range of clinical stigmata of which short stature, ovarian dysgenesis, and dysmorphic features are the most frequent. Morbidity and mortality are clearly increased compared with the general population, and the average age at diagnosis is quite delayed. Even if the majority of females with TS have a non-mosaic 45,X karyotype, several karyotype variations exist, including short or long arm deletion, ring X isochromosome of the long arm, and 45,X 46,XX mosaicism. This explains the large phenotypic and genetic heterogeneities of TS, which make the diagnosis and especially the management increasingly difficult. We present in this work a genetic study of TS in the Tunisian population to establish a genotype–phenotype correlation, which would be of great help for the diagnosis and the care of patients. Patients and methods A total of 26 unrelated Tunisian girls were included in this study. All patients underwent a complete clinical and biochemical examination as well as karyotyping. The screening for the SRY gene was carried out by fluorescence in-situ hybridization or by PCR. Results Cytogenetic results showed a prevalence of the 45,X karyotype in 46% of patients and various proportions of the other karyotypes. However, genotype–phenotype correlation revealed several discrepancies regarding the major signs and the age at diagnosis. The comparison of the approaches used for the screening of the SRY gene showed that karyotyping is unable to detect low 45,X/46,XY mosaicism and that it is the PCR that would be able to do, eliciting its role to make a reliable diagnosis. Conclusion The karyotype alone is not sufficient to make a TS diagnosis in cases of weak mosaicism, and the great heterogeneity that reigns the syndrome elicits an epigenetic and transcriptomic exploration of several genes that recently seem to be involved in the disease.

Keywords

• epigenetic
• genotype–phenotype correlation
• karyotype
• turner syndrome