Intrauterine phenotype features of fetuses with Williams-Beuren syndrome and literature review

Antenatal ultrasound features of isolated recurrent copy number variation in 7q11.23 (Williams syndrome and 7q11.23 duplication syndrome)

OBJECTIVE

We aimed to gather fetal cases carrying a 7q11.23 copy number variation (CNV) and collect precise clinical data to broaden knowledge of antenatal features in these syndromes.

METHODS

We retrospectively recruited unrelated cases with 7q11.23 deletion, known as Williams-Beuren syndrome (WBS), or 7q11.23 duplication who had prenatal ultrasound findings. We collected laboratory and clinical data, fetal ultrasound, cardiac ultrasound and fetal autopsy reports from 18 prenatal diagnostic centers throughout France.

RESULTS

40 fetuses with WBS were collected and the most common features were intra-uterine growth retardation (IUGR) (70.0%, 28/40), cardiovascular defects (30.0%, 12/40), polyhydramnios (17.5%, 7/40) and protruding tongue (15.0%, 6/40). Fetal autopsy reports were available for 11 cases and were compared with ultrasound prenatal features. Four cases of fetuses with 7q11.23 microduplication were collected and prenatal ultrasound signs were variable and often isolated.

CONCLUSION

This work strengthens the fact that 7q11.23 CNVs are associated with a broad spectrum of antenatal presentations. IUGR and cardiovascular defects were the most frequent ultrasound signs. By reporting the biggest series of antenatal WBS, we aim to better delineate distinctive signs in fetuses with 7q11.23 CNVs.

Prenatal phenotype features and genetic etiology of the Williams-Beuren syndrome and literature review

Objective

To share our experience on prenatal diagnosis of Williams-Beuren syndrome(WBS) and to improve the awareness, diagnosis, and intrauterine monitoring of the fetuses of this disease.

Methods

The study retrospectively evaluated 14 cases of WBS diagnosed prenatally by single nucleotide polymorphism array (SNP-array). Clinical data from these cases were systematically reviewed, including maternal demographics, indications for invasive prenatal diagnosis, ultrasound findings, SNP-array results, trio-medical exome sequencing (Trio-MES) results, QF-PCR results, pregnancy outcomes and follow-ups.

Results

A total of 14 fetuses were diagnosed with WBS and their prenatal phenotypes were assessed retrospectively. In our case series, the most common ultrasound features were intrauterine growth retardation (IUGR), congenital cardiovascular defects, abnormal fetal placental doppler indices, thickened nuchal translucency(NT) and polyhydramnios. Other less common ultrasound features include fetal hydrops, hydroderma, bilateral pleural effusion, subependymal cysts, etc. Parental chromosome analysis was performed in seven pairs of parents, and all the deletions on chromosome 7q11.23 were de novo.

Conclusion

Prenatal ultrasound features of WBS cases are highly variable, with IUGR, cardiovascular abnormalities and abnormal fetal placental doppler indices, being the most common intrauterine phenotypes. Our case series expand the intrauterine phenotypes of WBS, including cardiovascular abnormalities right aortic arch(RAA) combined with persistent right umbilical vein(PRUV) and elevated the ratio of end-systolic peak flow velocity to end-diastonic peak flow velocity(S/D). In the meantime, with the decrease in the cost of the next-generation sequencing, the method may become widely used in prenatal diagnosis in the near future.

Mid-trimester isolated bilateral rocker bottom feet leading to prenatal diagnosis of 7q11.23 microdeletion: Williams syndrome

Prenatal sonographic depiction of congenital vertical talus (rocker bottom feet), describing a prominent calcaneus and rounded convex appearance of the ventral aspect of the foot, has been reported with fetal Trisomies 18, 13, 9 HOXD10 mutations and recently 2q13 microdeletion. We present a 24 year old in whom mid-trimester sonographic finding of isolated bilateral rocker bottom feet led to diagnosis of 7q11.23 microdeletion-Williams syndrome. This association has not been reported previously. This case emphasizes the critical assessment of detail microarray upon prenatal sonographic notation of abnormal structural fetal features.

Prenatal diagnosis of Williams-Beuren syndrome by ultrasound and chromosomal microarray analysis

Background

There are a few literature reports of prenatal ultrasound manifestations of Williams-Beuren syndrome. We aimed to explore the prenatal diagnosis of Williams-Beuren syndrome by ultrasound and chromosomal microarray analysis and describe the prenatal ultrasound performance of this syndrome.

Methods

In this retrospective study, we reported eight cases of Williams-Beuren syndrome diagnosed at our prenatal diagnostic center from 2016 to 2021. We systematically reviewed clinical data from these cases, including indications for invasive testing, sonographic findings, QF-PCR results, chromosomal microarray analysis results, and pregnancy outcomes.

Results

In this study, the common ultrasound features were ventricular septal defect (37.5%), intrauterine growth retardation (25%), and aortic coarctation (25%). Moreover, all patients were found to have a common deletion in the Williams-Beuren syndrome chromosome region at the 7q11.23 locus, which contained the elastin gene. Deletion sizes ranged from 1.42 to 2.07 Mb. Seven parents asked for termination of pregnancy, and one patient was lost to follow-up.

Conclusions

This study is the most extensive prenatal study using chromosomal microarray analysis technology for detailed molecular analysis of Williams-Beuren syndrome cases. We reported three cases combined with first-reported ultrasound manifestations. Case 1 was concomitant with multicystic dysplastic kidney and duodenal atresia combined with case 3. Notably, case 4 was combined with multiple cardiovascular malformations: Tetralogy of Fallot, right aortic arch, and supravalvar aortic stenosis. These manifestations expand the intrauterine ultrasound phenotype of Williams-Beuren syndrome in previous literature reports.

Genetic Background of Fetal Growth Restriction

Fetal growth restriction (FGR) is one of the most formidable challenges in present-day antenatal care. Pathological fetal growth is a well-known factor of not only in utero demise in the third trimester, but also postnatal morbidity and unfavorable developmental outcomes, including long-term sequalae such as metabolic diseases, diabetic mellitus or hypertension. In this review, the authors present the current state of knowledge about the genetic disturbances responsible for FGR diagnosis, divided into fetal, placental and maternal causes (including preeclampsia), as well as their impact on prenatal diagnostics, with particular attention on chromosomal microarray (CMA) and noninvasive prenatal testing technique (NIPT).

Chromosomal Microarray Analysis for the Fetuses with Aortic Arch Abnormalities and Normal Karyotype

Background

Aortic arch abnormalities (AAA) are abnormal embryologic developments of the aorta and its branches. Their outcomes often depend on their association with other congenital diseases and genetic testing results.

Objective

This study aimed to evaluate the yield of chromosomal microarray analysis (CMA) in fetuses with different patterns of AAA and normal karyotype.

Methods

Data from 158 pregnancies referred for prenatal CMA testing due to fetal AAA were obtained between April 2016 and April 2019. Fetuses with isolated AAA, AAA accompanied by soft ultrasound markers, and AAA with other ultrasound malformations were classified into groups A, B, and C, respectively. Cases with detectable karyotype aberrations were excluded from the study.

Results

Twenty cases (12.7%) of submicroscopic anomalies were detected in 158 cases with normal karyotype, comprising 16 cases (10.1%) of clinically significant variants, two cases (1.3%) of variants of unknown significance, and two variants (1.3%) that were likely benign. Microdeletion of 22q11.2 accounted for 25% (4/16) of the clinically significant variants. The overall incremental yields by CMA in group A, group B, and group C were 1.8%, 2.3%, and 24.1%, respectively. Except for double aortic arch, the incremental yield of clinical significant findings for each type of AAA in group C was much higher than that in group A and group B. In group A, a clinically significant variant was only detected in one fetus with right aortic arch (RAA) (1.8%, 1/57).

Conclusions

In addition to 22q11.2 microdeletion, many other clinically significant submicroscopic variants are present in fetuses with AAA, especially in fetuses with other ultrasound malformations. Although CMA is always recommended in the presence of any malformation in many countries, our results suggest insufficient evidence to recommend CMA in fetuses with isolated AAA, except for isolated RAA.

Investigation on combined copy number variation sequencing and cytogenetic karyotyping for prenatal diagnosis

Background

We aimed to evaluate the clinical value of copy number variation-sequencing (CNV-Seq) in combination with cytogenetic karyotyping in prenatal diagnosis.

Methods

CNV-Seq and cytogenetic karyotyping were performed in parallel for 9452 prenatal samples for comparison of the diagnostic performance of the two methods, and to evaluate the screening performance of maternal age, maternal serum screening, fetal ultrasound scanning and noninvasive prenatal testing (NIPT) for fetal pathogenic copy number variation (CNV).

Results

Among the 9452 prenatal samples, traditional karyotyping detected 704 cases (7.5%) of abnormal cytogenetic karyotypes, 171 (1.8%) chromosome polymorphism, 20 (0.2%) subtle structural variations, 74 (0.7%) mutual translocation (possibly balanced), 52 (0.6%) without karyotyping results, and 8431 (89.2%) normal cytogenetic karyotypes. Among the 8705 cases with normal karyotype, polymorphism, mutual translocation, or marker chromosome, CNV-Seq detected 63 cases (0.7%) of pathogenic chromosome microdeletion/duplication. Retrospectively, noninvasive prenatal testing (NIPT) had high sensitivity and specificity for the screening of fetal pathogenic CNV, and NIPT combining with maternal age, maternal serum screening or fetal ultrasound scanning, which improved the screening performance.

Conclusion

The combined application of cytogenetic karyotyping and CNV-Seq significantly improved the detection rate of fetal pathogenic chromosome microdeletion/duplication. NIPT was recommended for the screening of pathogenic chromosome microdeletion/duplication, and NIPT combining with other screening methods further improved the screening performance for pathogenic fetal CNV.

Williams syndrome

Williams syndrome (WS) is a relatively rare microdeletion disorder that occurs in as many as 1:7,500 individuals. WS arises due to the mispairing of low-copy DNA repetitive elements at meiosis. The deletion size is similar across most individuals with WS and leads to the loss of one copy of 25-27 genes on chromosome 7q11.23. The resulting unique disorder affects multiple systems, with cardinal features including but not limited to cardiovascular disease (characteristically stenosis of the great arteries and most notably supravalvar aortic stenosis), a distinctive craniofacial appearance, and a specific cognitive and behavioural profile that includes intellectual disability and hypersociability. Genotype-phenotype evidence is strongest for ELN, the gene encoding elastin, which is responsible for the vascular and connective tissue features of WS, and for the transcription factor genes GTF2I and GTF2IRD1, which are known to affect intellectual ability, social functioning and anxiety. Mounting evidence also ascribes phenotypic consequences to the deletion of BAZ1B, LIMK1, STX1A and MLXIPL, but more work is needed to understand the mechanism by which these deletions contribute to clinical outcomes. The age of diagnosis has fallen in regions of the world where technological advances, such as chromosomal microarray, enable clinicians to make the diagnosis of WS without formally suspecting it, allowing earlier intervention by medical and developmental specialists. Phenotypic variability is considerable for all cardinal features of WS but the specific sources of this variability remain unknown. Further investigation to identify the factors responsible for these differences may lead to mechanism-based rather than symptom-based therapies and should therefore be a high research priority.