Marisol Soto

It is evident that Turner syndrome (TS) impacts almost all developmental stages of the fetal heart with congenital heart disease (CHD) being seen in 23%–50% of individuals. Although the spectrum of CHDs in TS is well‐established, with left‐sided lesions predominating, the influence of specific karyotypes on the prevalence and types of CHDs remains incompletely understood. The primary objective of this systematic review/meta‐analysis was to quantitatively synthesize the existing evidence on the association between specific karyotypes in TS and the risk of various CHDs. A systematic literature search was conducted through December 2023 to identify studies reporting the prevalence of CHDs in relation to TS karyotype. The quality of the individual studies was assessed using the Joanna Briggs Institute critical appraisal tools for systematic reviews. The overall estimates were pooled using both fixed‐ and random‐effects models. Sensitivity and subgroup analysis were performed. Twenty‐five studies were included in the analysis. TS individuals with a 45,X karyotype showed a significantly higher likelihood of bicuspid aortic valve (BAV) (pooled OR, 3.14 [95% CI: 2.49–3.94]), aortic coarctation (CoA) (pooled OR, 4.16 [95% CI: 2.74–6.31]), and partial anomalous pulmonary venous return (PAPVR) (pooled OR, 4.86 [2.31–10.2]) compared with TS individuals with a non‐45,X karyotype. In addition, TS individuals with a 45,X karyotype also showed a significantly higher likelihood of BAV (pooled OR, 2.72 [95% CI: 1.62–4.56]) when compared with TS individuals with 45,X/46,XX mosaicism. TS individuals with a 45,X karyotype showed a significantly higher risk of BAV (pooled OR, 2.13 [95% CI: 1.42–3.21]) and CoA (pooled OR, 4.52 [95% CI: 1.58–13.0]) when compared with TS individuals with an isochromosome Xq. A significantly higher likelihood of BAV was also found in 45,X compared to other karyotypes (e.g., 45,X/46,XY and TS karyotypes with ring X chromosome). Some heterogeneity was evident, but publication was low. This meta‐analysis confirms a strong association between the 45,X karyotype and increased prevalence of BAV, CoA, and PAPVR in TS. While 45,X/46,XX mosaicism and karyotypes with an isochromosome Xq mitigate risk, the findings emphasize the need for large‐scale studies to refine risk assessment and management strategies.

Turner syndrome (TS) is a chromosomal disorder that is caused by a missing or structurally abnormal second sex chromosome. Subjects with TS are at an increased risk of developing intrauterine growth retardation, low birth weight, short stature, congenital heart diseases, infertility, obesity, dyslipidemia, hypertension, insulin resistance, type 2 diabetes mellitus, metabolic syndrome, and cardiovascular diseases (stroke and myocardial infarction). The underlying pathogenetic mechanism of TS is unknown. The assumption that X chromosome-linked gene haploinsufficiency is associated with the TS phenotype is questioned since such genes have not been identified. Thus, other pathogenic mechanisms have been suggested to explain this phenotype. Morphogenesis encompasses a series of events that includes cell division, the production of migratory precursors and their progeny, differentiation, programmed cell death, and integration into organs and systems. The precise control of the growth and differentiation of cells is essential for normal development. The cell cycle frequency and the number of proliferating cells are essential in cell growth. 45,X cells have a failure to proliferate at a normal rate, leading to a decreased cell number in a given tissue during organogenesis. A convergence of data indicates an association between a prolonged cell cycle and the phenotypical features in Turner syndrome. This review aims to examine old and new findings concerning the relationship between a prolonged cell cycle and TS phenotype. These studies reveal a diversity of phenotypic features in TS that could be explained by reduced cell proliferation. The implications of this hypothesis for our understanding of the TS phenotype and its pathogenesis are discussed. It is not surprising that 45,X monosomy leads to cellular growth pathway dysregulation with profound deleterious effects on both embryonic and later stages of development. The prolonged cell cycle could represent the beginning of the pathogenesis of TS, leading to a series of phenotypic consequences in embryonic/fetal, neonatal, pediatric, adolescence, and adulthood life.

Background: It is possible that genes on the X chromosome are expressed differently depending of its parental origin. The objective of this study was to determine the influence of the parental origin of the X-chromosome on phenotypic variability, response to rhGH and on the biochemical profile of TS patients.Methods: This was a cross-sectional multicenter correlational study carried out over three years in six Latin-American university hospitals. Unrelated 45,X TS patients (n = 93; 18.3 ± 8.5 years )) were evaluated. A subgroup (n = 34) of the patients were prospectively treated with rhGH over two years. DNA profiles of patients and their mothers were compared to determine the parental origin of the retained X-chromosome through 10 polymorphic X-chromosome-STRs. The association with clinical features, biochemical profiles and anthropometric data at the beginning and after two years of rhGH treatment was determined.Results: Seventy two percent of patients retained the maternal X chromosome (Xm). A trend towards significance between maternal height and patients final height (p ≤ 0.07) in 45,Xm subjects was observed. There was no correlation between paternal height and patient height. No differences were detected between both groups in regard to dysmorphic features, classical malformations or increase in the height-SDS after rhGH. There were higher levels of triglycerides, total and LDL cholesterol in patients >20 years who retained the Xm.Conclusions: The parental origin of the retained X chromosome may influence lipid metabolism in TS patients, but its effect on growth seems to be minimal. No parental-origin-effect on the phenotypic features, associated anomalies and on the growth response to rhGH was found in 45,X TS individuals.