Turner Syndrome

PurposeMany women with X chromosome aneuploidy undergo lifetime clinical monitoring for possible complications. However, ascertainment of cases in the clinic may mean that the penetrance has been overestimated.MethodsWe characterized the prevalence and phenotypic consequences of X chromosome aneuploidy in a population of 244,848 women over 40 years of age from UK Biobank, using single-nucleotide polymorphism (SNP) array data.ResultsWe detected 30 women with 45,X; 186 with mosaic 45,X/46,XX; and 110 with 47,XXX. The prevalence of nonmosaic 45,X (12/100,000) and 47,XXX (45/100,000) was lower than expected, but was higher for mosaic 45,X/46,XX (76/100,000). The characteristics of women with 45,X were consistent with the characteristics of a clinically recognized Turner syndrome phenotype, including short stature and primary amenorrhea. In contrast, women with mosaic 45,X/46,XX were less short, had a normal reproductive lifespan and birth rate, and no reported cardiovascular complications. The phenotype of women with 47,XXX included taller stature (5.3 cm; SD = 5.52 cm; P = 5.8 × 10-20) and earlier menopause age (5.12 years; SD = 5.1 years; P = 1.2 × 10-14).ConclusionOur results suggest that the clinical management of women with 45,X/46,XX mosaicism should be minimal, particularly those identified incidentally.

Turner syndrome is caused by complete or partial loss of the second sex chromosome, occurring in ~1 in 2,000 female births. There is a greatly increased incidence of aortopathy of unknown etiology, including bicuspid aortic valve (BAV), thoracic aortic aneurysms, aortic dissection and rupture. We performed whole exome sequencing on 188 Turner syndrome participants from the National Registry of Genetically Triggered Thoracic Aortic Aneurysms and Cardiovascular Related Conditions (GenTAC). A gene-based burden test, the optimal sequence kernel association test (SKAT-O), was used to evaluate the data with BAV and aortic dimension z-scores as covariates. Genes on chromosome Xp were analyzed for the potential to contribute to aortopathy when hemizygous. Exome analysis revealed that TIMP3 was associated with indices of aortopathy at exome-wide significance (p = 2.27 x 10(-7)), which was replicated in a separate cohort. The analysis of Xp genes revealed that TIMP1, which is a functionally redundant paralogue of TIMP3, was hemizygous in >50% of our discovery cohort and that having only one copy of TIMP1 increased the odds of having aortopathy (OR = 9.76, 95% CI = 1.91-178.80, p = 0.029). The combinatorial effect of a single copy of TIMP1 and TIMP3 risk alleles further increased the risk for aortopathy (OR = 12.86, 95% CI = 2.57-99.39, p = 0.004). The products of genes encoding tissue inhibitors of matrix metalloproteinases (TIMPs) are involved in development of the aortic valve and protect tissue integrity of the aorta. We propose that the combination of X chromosome TIMP1 hemizygosity and variants of its autosomal paralogue TIMP3, significantly increases the risk of aortopathy in Turner syndrome.

BackgroundMonosomy of the X chromosome is the most frequent genetic abnormality in human as it is present in approximately 2% of all conceptions, although 99% of these embryos are spontaneously miscarried. In postnatal life, clinical features of Turner syndrome may include typical dysmorphic stigmata, short stature, sexual infantilism, and renal, cardiac, skeletal, endocrine and metabolic abnormalities.Main textTurner syndrome is due to a partial or total loss of the second sexual chromosome, resulting in the development of highly variable clinical features. This phenotype may not merely be due to genomic imbalance from deleted genes but may also result from additive influences on associated genes within a given gene network, with an altered regulation of gene expression triggered by the absence of the second sex chromosome. Current studies in human and mouse models have demonstrated that this chromosomal abnormality leads to epigenetic changes, including differential DNA methylation in specific groups of downstream target genes in pathways associated with several clinical and metabolic features, mostly on autosomal chromosomes. In this article, we begin exploring the potential involvement of both genetic and epigenetic factors in the origin of X chromosome monosomy. We review the dispute between the meiotic and post-zygotic origins of 45,X monosomy, by mainly analyzing the findings from several studies that compare gene expression of the 45,X monosomy to their euploid and/or 47,XXX trisomic cell counterparts on peripheral blood mononuclear cells, amniotic fluid, human fibroblast cells, and induced pluripotent human cell lines. From these studies, a profile of epigenetic changes seems to emerge in response to chromosomal imbalance. An interesting finding of all these studies is that methylation-based and expression-based pathway analyses are complementary, rather than overlapping, and are correlated with the clinical picture displayed by TS subjects.ConclusionsThe clarification of these possible causal pathways may have future implications in increasing the life expectancy of these patients and may provide informative targets for early pharmaceutical intervention.

BACKGROUNDEstrogen deficiency and progressive hearing loss (HL) are significant concerns in individuals with Turner syndrome (TS). However, whether childhood estrogen deficiency increases HL risk and whether estrogen replacement therapy (ERT) prevents hearing deterioration are still unclear.METHODSThis prospective cohort study recruited children with TS from a tertiary referral center between 2016 and 2024. All participants received standardized recombinant human growth hormone therapy. Longitudinal monitoring data of hormone levels, metabolic parameters, and annual audiological examinations were recorded. The primary analysis used a multivariate Cox model to estimate the adjusted hazard ratio (HR) of hearing loss between estrogen-deficient and estrogen-normal TS patients without prior exogenous estrogen exposure. The secondary analysis compared annual pure tone average (PTA) and its changes between the ERT and non-ERT groups in a substudy.RESULTSAmong 87 prepubertal pediatric patients with TS, 48 (55.2%) were estrogen deficient, and 38 HL events occurred over a 35-month median follow-up. The estrogen-deficient group had higher HL incidence (27 cases, 56.3%; 20.6 per 100 person-years [PY]) versus estrogen-normal (11 cases, 28.2%; 8.6 per 100 PY), with estrogen deficiency independently increasing HL risk (HR 2.93, 95% CI 1.21-7.12). Notably, estrogen deficiency also independently predicted abnormal distortion product otoacoustic emissions with an even higher effect size (HR 3.98, 95% CI 1.35-11.76). The substudy found that initiating ERT at the age of 12 significantly preserve auditory function, with the ERT group showing markedly lower PTA and slower hearing deterioration (-1.24 dB/year vs. 1.13 dB/year right ear; -1.85 dB/year vs. 1.04 dB/year left ear, P = 0.001).CONCLUSIONChildhood estrogen deficiency is a modifiable risk factor. Initiating ERT around early adolescence may help hearing preservation.TRIAL REGISTRATIONChinese Clinical Trial Registry: ChiCTR2300068063.FUNDINGNational Natural Science Foundation of China (grants 82173154 and 82471155), Fundamental Research Funds for the Central Universities Clinical Research 5010 Program (Sun Yat-sen University, no. 2024004).