A highly sensitive, high-throughput assay for the detection of Turner syndrome

Clinical practice guidelines for the care of girls and women with Turner syndrome

Turner syndrome (TS) affects 50 per 100 000 females. TS affects multiple organs through all stages of life, necessitating multidisciplinary care. This guideline extends previous ones and includes important new advances, within diagnostics and genetics, estrogen treatment, fertility, co-morbidities, and neurocognition and neuropsychology. Exploratory meetings were held in 2021 in Europe and United States culminating with a consensus meeting in Aarhus, Denmark in June 2023. Prior to this, eight groups addressed important areas in TS care: (1) diagnosis and genetics, (2) growth, (3) puberty and estrogen treatment, (4) cardiovascular health, (5) transition, (6) fertility assessment, monitoring, and counselling, (7) health surveillance for comorbidities throughout the lifespan, and (8) neurocognition and its implications for mental health and well-being. Each group produced proposals for the present guidelines, which were meticulously discussed by the entire group. Four pertinent questions were submitted for formal GRADE (Grading of Recommendations, Assessment, Development and Evaluation) evaluation with systematic review of the literature. The guidelines project was initiated by the European Society for Endocrinology and the Pediatric Endocrine Society, in collaboration with members from the European Society for Pediatric Endocrinology, the European Society of Human Reproduction and Embryology, the European Reference Network on Rare Endocrine Conditions, the Society for Endocrinology, and the European Society of Cardiology, Japanese Society for Pediatric Endocrinology, Australia and New Zealand Society for Pediatric Endocrinology and Diabetes, Latin American Society for Pediatric Endocrinology, Arab Society for Pediatric Endocrinology and Diabetes, and the Asia Pacific Pediatric Endocrine Society. Advocacy groups appointed representatives for pre-meeting discussions and the consensus meeting.

Age at and indication for diagnosis of Turner syndrome in the pediatric population

Early diagnosis of Turner syndrome (TS) enables timely intervention and may improve outcomes, but many are still diagnosed late. The objectives of our study were to describe the age and clinical features leading to diagnosis of TS in a large referral center. We hypothesize that newer testing modalities, such as noninvasive prenatal testing (NIPT), may lead to a decline in the age of diagnosis. Medical records of TS patients followed at The Cincinnati Center for Pediatric and Adult TS Care between 1997 and 2016 were reviewed for age at diagnosis, karyotype, and clinical indication(s). Patients (<18 years) were included (n = 239). Thirty-seven percent of patients were diagnosed prenatally or neonatally (≤1 month). The median age of diagnosis was 1.5 (IQR 0.0-10.0) years. If not made during those periods, the median age was 9.3 (IQR 3.2-12.5) years. The most common indications for diagnosis were before birth, unspecified prenatal testing (57%); in neonates/infants, lymphedema (21%); in childhood, short stature (72%); and in adolescence, short stature (45%) followed by pubertal delay with short stature (22%). The age of TS diagnosis in our cohort is young. However, when the diagnosis is not made before 1 year, the median age of diagnosis has not changed in recent years. The age at diagnosis could decrease with prenatal testing, although our study may not have assessed a long enough period of increased use of NIPT. Together with an increase in provider clinical awareness, this may result in more age-appropriate screening of comorbidities and earlier therapeutic intervention.

Gene Copy Number Quantification of SHOX, VAMP7, and SRY for the Detection of Sex Chromosome Aneuploidies in Neonates

Aims: To explore the feasibility of detecting sex chromosome aneuploidies (SCAs) by means of gene copy number quantification of short stature homeobox (SHOX), vesicle-associated membrane protein 7 (VAMP7), and SRY in newborns. Materials and Methods: Gene doses of SHOX, VAMP7, and SRY were determined by quantitative polymerase chain reaction (qPCR) using DNA obtained from dried blood samples from newborns. Relative quantification values were obtained. An aneuploidy profile was established according to cutoff values. Samples with ≥2 gene doses (out of range) were reanalyzed, and those with aneuploidy profiles were confirmed by karyotyping. Sensitivity, specificity, and positive and negative predictive values were obtained. Results: A total of 10,033 samples were collected (4945 females and 5088 males). Of 244 (2.43%) samples with ≥2 gene doses that were retested, 20 cases were confirmed. The overall incidence of SCAs was 1 in 500 live newborns. There were six cases of Turner syndrome (1/824), 3 cases of XXX (1/1648), 7 cases of Klinefelter syndrome (1/726), and 4 cases of of XYY (1/1272). The sensitivity was 0.952 (95.42%); the specificity was 0.975 (97.56%); the positive predictive value was 0.909 (90.91%) and the negative predictive value was 0.987 (98.77%). Conclusions: Gene copy number analyses of the VAMP7, SHOX, and SRY genes by qPCR from blood samples spotted onto filter paper is a highly reliable method for the early detection of male and female SCAs.

Clinical practice guidelines for the care of girls and women with Turner syndrome: proceedings from the 2016 Cincinnati International Turner Syndrome Meeting

Turner syndrome affects 25-50 per 100,000 females and can involve multiple organs through all stages of life, necessitating multidisciplinary approach to care. Previous guidelines have highlighted this, but numerous important advances have been noted recently. These advances cover all specialty fields involved in the care of girls and women with TS. This paper is based on an international effort that started with exploratory meetings in 2014 in both Europe and the USA, and culminated with a Consensus Meeting held in Cincinnati, Ohio, USA in July 2016. Prior to this meeting, five groups each addressed important areas in TS care: 1) diagnostic and genetic issues, 2) growth and development during childhood and adolescence, 3) congenital and acquired cardiovascular disease, 4) transition and adult care, and 5) other comorbidities and neurocognitive issues. These groups produced proposals for the present guidelines. Additionally, four pertinent questions were submitted for formal GRADE (Grading of Recommendations, Assessment, Development and Evaluation) evaluation with a separate systematic review of the literature. These four questions related to the efficacy and most optimal treatment of short stature, infertility, hypertension, and hormonal replacement therapy. The guidelines project was initiated by the European Society for Endocrinology and the Pediatric Endocrine Society, in collaboration with The European Society for Pediatric Endocrinology, The Endocrine Society, European Society of Human Reproduction and Embryology, The American Heart Association, The Society for Endocrinology, and the European Society of Cardiology. The guideline has been formally endorsed by the European Society for Endocrinology, the Pediatric Endocrine Society, the European Society for Pediatric Endocrinology, the European Society of Human Reproduction and Embryology and the Endocrine Society. Advocacy groups appointed representatives who participated in pre-meeting discussions and in the consensus meeting.

Whole-Exome Sequencing for Diagnosis of Turner Syndrome: Toward Next-Generation Sequencing and Newborn Screening

CONTEXT

Turner syndrome (TS) is due to a complete or partial loss of an X chromosome in female patients and is not currently part of newborn screening (NBS). Diagnosis is often delayed, resulting in missed crucial diagnostic and therapeutic opportunities.

OBJECTIVES

This study sought to determine if whole-exome sequencing (WES) as part of a potential NBS program could be used to diagnose TS.

DESIGN, SETTING, PATIENTS

Karyotype, chromosomal microarray, and WES were performed on blood samples from women with TS (n = 27) enrolled in the Personalized Genomic Research study at the National Institutes of Health. Female control subjects (n = 37) and male subjects (n = 27) also underwent WES. Copy number variation was evaluated using EXCAVATOR2 and B allele frequency was calculated from informative single nucleotide polymorphisms. Simulated WES data were generated for detection of low-level mosaicism and complex structural chromosome abnormalities.

RESULTS

We detected monosomy for chromosome X in all 27 TS samples, including 1 mosaic for 45,X/46,XX and another with previously unreported material on chromosome Y. Sensitivity and specificity were both 100% for the diagnosis of TS with no false-positive or false-negative results. Using simulated WES data, we detected isochromosome Xq and low-level mosaicism as low as 5%.

CONCLUSION

We present an accurate method of diagnosing TS using WES, including cases with low-level mosaicism, isochromosome Xq, and cryptic Y-chromosome material. Given the potential use of next-generation sequencing for NBS in many different diseases and syndromes, we propose WES can be used as a screening test for TS in newborns.

Multiplex Ligation-Dependent Probe Amplification Accurately Detects Turner Syndrome in Girls with Short Stature

AIMS

We aimed at evaluating a standard multiplex ligation-dependent probe amplification (MLPA) probe set for the detection of aneuploidy to diagnose Turner syndrome (TS). We first fixed an MLPA ratio cutoff able to detect all cases of TS in a pilot TS group. We then tested this value on a second group of TS patients and a short-stature population to measure specificity and sensitivity.

METHODS

15 TS patients with X mosaicism or X structural abnormalities (Pilot TS Group), 45 TS karyotype-assessed patients (TS Group), and 74 prepubertal female patients with apparent idiopathic short stature (Short-Stature Group) were enrolled. All subjects underwent MLPA and karyotype analysis. In the TS and Short-Stature Groups, MLPA testing was performed in blind.

RESULTS

The choice of an MLPA threshold ratio of 0.76 for at least 1 probe allowed us to detect all TS cases, including mosaicisms. Sensitivity and specificity were 100% (CI 95%, 0.92-1) and 88.89% (CI 95%, 0.79-0.94), respectively. The positive predictive value was 88.5%, and the negative predictive value was 100%. MLPA detected the presence of Y chromosome material in 2 patients.

CONCLUSION

MLPA is an accurate and inexpensive tool to screen for TS in girls with short stature. A customized MLPA kit may be useful for the screening of an even larger population.

The prevalence of turner syndrome in girls presenting with coarctation of the aorta

OBJECTIVE

To determine the prevalence of Turner syndrome in girls presenting with coarctation of the aorta (CoA).

STUDY DESIGN

A total of 132 girls with known structural CoA was identified. Those girls who had no previous karyotype analysis performed were asked to participate in a research study in which a banded karyotype with 50-cell count was performed.

RESULTS

Of 132 girls with CoA, 55 (41.7%) had karyotype analysis within 6 months of cardiac diagnosis. Three girls underwent karyotyping later because of clinical concerns. Of the 74 girls with CoA who had not had a karyotype, 38 (51.4%) consented to the study. Results were available for 37 girls. All were 46,XX. Five patients with Turner syndrome were identified in the 95 girls with CoA who had karyotype analysis (4 from early karyotype and 1 diagnosed later), which translated into a minimum prevalence of 5.3% of Turner syndrome in this group of girls with CoA. In addition, one infant with a 20-cell 46,XX karyotype had features of Turner syndrome.

CONCLUSION

Our study demonstrated for the first time in a large cohort that 5.3% of girls presenting with CoA are found to have Turner syndrome when karyotyping is performed. Given the spectrum of preventable and treatable health problems after the diagnosis of Turner syndrome, we believe that all girls with CoA should have a karyotype analysis, ideally with at least 50-cell count, at the time of diagnosis of CoA.

Single-nucleotide polymorphism array genotyping is equivalent to metaphase cytogenetics for diagnosis of Turner syndrome

PURPOSE

Turner syndrome is a developmental disorder caused by partial or complete monosomy for the X chromosome in 1 in 2,500 females. We hypothesized that single-nucleotide polymorphism (SNP) array genotyping could provide superior resolution in comparison to metaphase karyotype analysis to facilitate genotype-phenotype correlations.

METHODS

We genotyped 187 Turner syndrome patients with 733,000 SNP marker arrays. All cases met diagnostic criteria for Turner syndrome based on karyotypes (60%) or characteristic physical features. The SNP array results confirmed the diagnosis of Turner syndrome in 100% of cases.

RESULTS

We identified a single X chromosome (45,X) in 113 cases. In 58 additional cases (31%), other mosaic cell lines were present, including isochromosomes (16%), rings (5%), and Xp deletions (8%). The remaining cases were mosaic for monosomy X and normal male or female cell lines. Array-based models of X chromosome structure were compatible with karyotypes in 104 of 116 comparable cases (90%). We found that the SNP array data did not detect X-autosome translocations (three cases) but did identify two derivative Y chromosomes and 13 large copy-number variants that were not detected by karyotyping.

CONCLUSION

Our study is the first systematic comparison between the two methods and supports the utility of SNP array genotyping to address clinical and research questions in Turner syndrome.

Clinical review: Turner syndrome: updating the paradigm of clinical care

CONTEXT

Turner syndrome (TS), in which there is loss of all or part of one sex chromosome, occurs in one in 2500 live-born females and is associated with characteristic findings. Detailed healthcare checklists and screening guidelines are commonly used to detect known complications affecting individuals with TS. Even with the use of these guidelines, there remains an increased morbidity and mortality seen in TS as compared to the general population, leading to significant controversy on optimal management of several aspects of TS.

EVIDENCE ACQUISITION AND SYNTHESIS

A PubMed search of articles from the past 15 yr identified available studies related to the diagnosis and management of common issues related to TS as well as important historical articles. This review summarizes studies through January 2012 and highlights recent developments.

CONCLUSIONS

There remain many areas of uncertainty in the diagnosis and management of TS. Generalizations from experience in the care of other conditions in isolation (such as poor growth, follow-up of cardiac disease, or the treatment of ovarian failure) cannot be broadly applied when caring for individuals with TS. Specific differences include treatment of growth failure as early as possible; acquisition of adequate baseline cardiac studies, followed by serial magnetic resonance imaging, targeted to identify findings unique to TS that address the increased risk of aortic dissection; initiation of hormone replacement at the normal age of puberty, preferentially with transdermal estradiol; and detailed patient counseling to explain the long-term health risks commonly associated with this disorder. A revised paradigm of care using a standardized multidisciplinary evaluation, supplementing screening tests as advocated by expert opinion guidelines, can aid clinicians in interpreting the results of diagnostic testing in the context of TS. This approach optimizes medical care for women with TS and may reduce the increased morbidity and mortality currently seen in this population.

Molecular diagnostic testing for Klinefelter syndrome and other male sex chromosome aneuploidies

Background

Male sex chromosome aneuploidies are underdiagnosed despite concomitant physical and behavioral manifestations.

Objective

To develop a non-invasive, rapid and high-throughput molecular diagnostic assay for detection of male sex chromosome aneuploidies, including 47,XXY (Klinefelter), 47,XYY, 48,XXYY and 48,XXXY syndromes.

Methods

The assay utilizes three XYM and four XA markers to interrogate Y:X and X:autosome ratios, respectively. The seven markers were PCR amplified using genomic DNA isolated from a cohort of 323 males with aneuploid (n = 117) and 46,XY (n = 206) karyotypes. The resulting PCR products were subjected to Pyrosequencing, a quantitative DNA sequencing method.

Results

Receiver operator characteristic (ROC) curves were used to establish thresholds for the discrimination of aneuploid from normal samples. The XYM markers permitted the identification of 47,XXY, 48,XXXY and 47,XYY syndromes with 100% sensitivity and specificity in both purified DNA and buccal swab samples. The 48,XXYY karyotype was delineated by XA marker data from 46,XY; an X allele threshold of 43% also permitted detection of 48,XXYY with 100% sensitivity and specificity. Analysis of X chromosome-specific biallelic SNPs demonstrated that 43 of 45 individuals (96%) with 48,XXYY karyotype had two distinct X chromosomes, while 2 (4%) had a duplicate X, providing evidence that 48,XXYY may result from nondisjunction during early mitotic divisions of a 46,XY embryo.

Conclusions

Quantitative Pyrosequencing, with high-throughput potential, can detect male sex chromosome aneuploidies with 100% sensitivity.