Experience of chromosomal microarray applied in prenatal and postnatal settings in Hong Kong

A cohort study of neurodevelopmental disorders and/or congenital anomalies using high resolution chromosomal microarrays in southern Brazil highlighting the significance of ASD

Chromosomal microarray (CMA) is the reference in evaluation of copy number variations (CNVs) in individuals with neurodevelopmental disorders (NDDs), such as intellectual disability (ID) and/or autism spectrum disorder (ASD), which affect around 3-4% of the world's population. Modern platforms for CMA, also include probes for single nucleotide polymorphisms (SNPs) that detect homozygous regions in the genome, such as long contiguous stretches of homozygosity (LCSH). These regions result from complete or segmental chromosomal homozygosis and may be indicative of uniparental disomy (UPD), inbreeding, population characteristics, as well as replicative DNA repair events. In this retrospective study, we analyzed CMA reading files requested by geneticists and neurologists for diagnostic purposes along with available clinical data. Our objectives were interpreting CNVs and assess the frequencies and implications of LCSH detected by Affymetrix CytoScan HD (41%) or 750K (59%) platforms in 1012 patients from the south of Brazil. The patients were mainly children with NDDs and/or congenital anomalies (CAs). A total of 206 CNVs, comprising 132 deletions and 74 duplications, interpreted as pathogenic, were found in 17% of the patients in the cohort and across all chromosomes. Additionally, 12% presented rare variants of uncertain clinical significance, including LPCNVs, as the only clinically relevant CNV. Within the realm of NDDs, ASD carries a particular importance, owing to its escalating prevalence and its growing repercussions for individuals, families, and communities. ASD was one clinical phenotype, if not the main reason for referral to testing, for about one-third of the cohort, and these patients were further analyzed as a sub-cohort. Considering only the patients with ASD, the diagnostic rate was 10%, within the range reported in the literature (8-21%). It was higher (16%) when associated with dysmorphic features and lower (7%) for "isolated" ASD (without ID and without dysmorphic features). In 953 CMAs of the whole cohort, LCSH (≥ 3 Mbp) were analyzed not only for their potential pathogenic significance but were also explored to identify common LCSH in the South Brazilians population. CMA revealed at least one LCSH in 91% of the patients. For about 11.5% of patients, the LCSH suggested consanguinity from the first to the fifth degree, with a greater probability of clinical impact, and in 2.8%, they revealed a putative UPD. LCSH found at a frequency of 5% or more were considered common LCSH in the general population, allowing us to delineate 10 regions as potentially representing ancestral haplotypes of neglectable clinical significance. The main referrals for CMA were developmental delay (56%), ID (33%), ASD (33%) and syndromic features (56%). Some phenotypes in this population may be predictive of a higher probability of indicating a carrier of a pathogenic CNV. Here, we present the largest report of CMA data in a cohort with NDDs and/or CAs from the South of Brazil. We characterize the rare CNVs found along with the main phenotypes presented by each patient and show the importance and usefulness of LCSH interpretation in CMA results that incorporate SNPs, as well as we illustrate the value of CMA to investigate CNV in ASD.

Intrauterine ultrasound phenotyping, molecular characteristics, and postnatal follow-up of fetuses with the 15q11.2 BP1-BP2 microdeletion syndrome: a single-center, retrospective clinical study

OBJECTIVES

The 15q11.2 BP1-BP2 microdeletion is associated with neurodevelopmental diseases. However, most studies on this microdeletion have focused on adults and children. Thus, in this study, we summarized the molecular characteristics of fetuses with the 15q11.2 BP1-BP2 microdeletion and their postnatal follow-up to guide prenatal diagnosis.

METHODS

Ten thousand fetuses were retrospectively subjected to karyotype analysis and chromosome microarray analysis.

RESULTS

Chromosome microarray analysis revealed that 37 (0.4%) of the 10,000 fetuses had 15q11.2 BP1-BP2 microdeletions. The fragment size of the 15q11.2 BP1-BP2 region was approximately 312-855 kb and encompassed TUBGCP5, CYFIP1, NIPA2, and NIPA1 genes. Twenty-five of the 37 fetuses with this microdeletion showed phenotypic abnormalities. The most common ultrasonic structural abnormality was congenital heart disease, followed by renal dysplasia and Dandy-Walker malformation. The 15q11.2 BP1-BP2 microdeletion was inherited from the father and mother in 6 and 10 cases, respectively, and de novo inherited in 4 cases. In the postnatal follow-up, 16.1% of the children had postnatal abnormalities.

CONCLUSION

Fetuses with the 15q11.2 BP1-BP2 microdeletion showed high proportions of phenotypic abnormalities, but the specificity of penetrance was low. Thus, fetuses with this syndrome are potentially at a higher risk of postnatal growth/behavioral problems and require continuous monitoring of growth and development.

Combined use of karyotyping and copy number variation sequencing technology in prenatal diagnosis

Background

Karyotyping and genome copy number variation sequencing (CNV-seq) are two techniques frequently used in prenatal diagnosis. This study aimed to explore the diagnostic potential of using a combination of these two methods in order to provide a more accurate clinical basis for prenatal diagnosis.

Methods

We selected 822 pregnant women undergoing amniocentesis and separated them into six groups according to different risk indicators. Karyotyping and CNV-seq were performed simultaneously to compare the diagnostic performance of the two methods.

Results

Among the different amniocentesis indicators, abnormal fetal ultrasounds accounted for 39.29% of the total number of examinees and made up the largest group. The abnormal detection rate of non-invasive prenatal testing (NIPT) high risk was 37.93% and significantly higher than the other five groups (P < 0.05). The abnormal detection rate of mixed indicators was significantly higher than the history of the adverse reproductive outcomes group (P = 0.0151). The two methods combined found a total of 119 abnormal cases (14.48%). Karyotyping detected 57 cases (6.93%) of abnormal karyotypes, 30 numerical aberrations, and 27 structural aberrations. CNV-seq identified 99 cases (12.04%) with altered CNVs, 30 cases of chromosome aneuploidies, and 69 structural aberrations (28 pathogenic, eight that were likely pathogenic, and 33 microdeletion/duplication variants of uncertain significance (VUS)). Thirty-seven cases were found abnormal by both methods, 20 cases were detected abnormally by karyotyping (mainly mutual translocation and mostly balanced), and 62 cases of microdeletion/duplication were detected by CNV-seq. Steroid sulfatase gene (STS) deletion was identified at chromosome Xp22.31 in three cases. Postnatal follow-up confirmed that babies manifested skin abnormalities one week after birth. Six fetuses had Xp22.31 duplications ranging from 1.5 Kb to 1.7 Mb that were detected by CNV-seq. Follow-up showed that five babies presented no abnormalities during follow-up, except for one terminated pregnancy due to a history of adverse reproductive outcomes.

Conclusion

The combination of using CNV-seq and karyotyping significantly improved the detection rate of fetal pathogenic chromosomal abnormalities. CNV-seq is an effective complement to karyotyping and improves the accuracy of prenatal diagnosis.

Cardiovascular Anomalies among 1005 Fetuses Referred to Invasive Prenatal Testing-A Comprehensive Cohort Study of Associated Chromosomal Aberrations

This retrospective cohort study comprehensively evaluates cardiovascular anomalies (CVAs) and associated extracardiac structural malformations (ECMs) among 1005 fetuses undergoing invasive prenatal testing at a single tertiary Polish center in the context of chromosomal aberrations detected in them by array comparative genomic hybridization (aCGH) and G-band karyotyping. The results of our study show that CVAs are among the most common malformations detected in fetuses undergoing invasive prenatal testing, as they affected 20% of all cases seen in our department. Septal defects predominated among fetuses with numerical aberrations, while conotruncal defects were the most common findings among fetuses with pathogenic copy number variants (CNVs). In 61% of cases, CVAs were associated with ECMs (the diagnosis was confirmed postnatally or in cases of pregnancy termination by means of autopsy). The most common ECMs were anomalies of the face and neck, followed by skeletal defects. In total, pathogenic chromosomal aberrations were found in 47.5% of CVAs cases, including 38.6% with numerical chromosomal aberrations. Pathogenic CNVs accounted for 14.5% of cases with CVAs and normal karyotype. Thus, our study highlights the importance of assessing the anatomy of the fetus, and of the genetic testing (preferably aCGH) that should be offered in all CVA and ECM cases.

Genetic Analysis Algorithm for the Study of Patients with Multiple Congenital Anomalies and Isolated Congenital Heart Disease

Congenital anomalies (CA) affect 3–5% of newborns, representing the second-leading cause of infant mortality in Argentina. Multiple congenital anomalies (MCA) have a prevalence of 2.26/1000 births in newborns, while congenital heart diseases (CHD) are the most frequent CA with a prevalence of 4.06/1000 births. The aim of this study was to identify the genetic causes in Argentinian patients with MCA and isolated CHD. We recruited 366 patients (172 with MCA and 194 with isolated CHD) born between June 2015 and August 2019 at public hospitals. DNA from peripheral blood was obtained from all patients, while karyotyping was performed in patients with MCA. Samples from patients presenting conotruncal CHD or DiGeorge phenotype (n = 137) were studied using MLPA. Ninety-three samples were studied by array-CGH and 18 by targeted or exome next-generation sequencing (NGS). A total of 240 patients were successfully studied using at least one technique. Cytogenetic abnormalities were observed in 13 patients, while 18 had clinically relevant imbalances detected by array-CGH. After MLPA, 26 patients presented 22q11 deletions or duplications and one presented a TBX1 gene deletion. Following NGS analysis, 12 patients presented pathogenic or likely pathogenic genetic variants, five of them, found in KAT6B, SHH, MYH11, MYH7 and EP300 genes, are novel. Using an algorithm that combines molecular techniques with clinical and genetic assessment, we determined the genetic contribution in 27.5% of the analyzed patients.

Molecular Approaches in Fetal Malformations, Dynamic Anomalies and Soft Markers: Diagnostic Rates and Challenges-Systematic Review of the Literature and Meta-Analysis

Fetal malformations occur in 2-3% of pregnancies. They require invasive procedures for cytogenetics and molecular testing. "Structural anomalies" include non-transient anatomic alterations. "Soft markers" are often transient minor ultrasound findings. Anomalies not fitting these definitions are categorized as "dynamic". This meta-analysis aims to evaluate the diagnostic yield and the rates of variants of uncertain significance (VUSs) in fetuses undergoing molecular testing (chromosomal microarray (CMA), exome sequencing (ES), genome sequencing (WGS)) due to ultrasound findings. The CMA diagnostic yield was 2.15% in single soft markers (vs. 0.79% baseline risk), 3.44% in multiple soft markers, 3.66% in single structural anomalies and 8.57% in multiple structural anomalies. Rates for specific subcategories vary significantly. ES showed a diagnostic rate of 19.47%, reaching 27.47% in multiple structural anomalies. WGS data did not allow meta-analysis. In fetal structural anomalies, CMA is a first-tier test, but should be integrated with karyotype and parental segregations. In this class of fetuses, ES presents a very high incremental yield, with a significant VUSs burden, so we encourage its use in selected cases. Soft markers present heterogeneous CMA results from each other, some of them with risks comparable to structural anomalies, and would benefit from molecular analysis. The diagnostic rate of multiple soft markers poses a solid indication to CMA.

High rate of abnormal findings in Prenatal Exome Trio in low risk pregnancies and apparently normal fetuses

OBJECTIVE

Data on the value of exome sequencing in fetuses with no structural anomalies are limited, especially in the early stages of pregnancy and in low risk pregnancies. We investigated the yield of targeted clinical prenatal trio exome sequencing (pES) in pregnancies with and without fetal structural anomalies.

METHODS

We performed pES in 353 pregnancies: Group 1 included 143 pregnancies with high clinical suspicion for a genetic disease: pregnancies with increased nuchal translucency, ultrasound structural defects, intrauterine growth restriction, polyhydramnios, or effusion/nuchal edema. Group 2 included 210 pregnancies with no notable abnormal fetal ultrasound findings. 2a. Low risk pregnancies with minor ultrasound findings, referred to the geneticist due to mildly increased risk for genetic disease (50); and 2b. Normal pregnancy surveillance (160).

RESULTS

Overall, 26 (7.36%) fetal analyses had pathogenic (P)/likely pathogenic (LP) variants. In group 1, 20/143 (13.99%) cases had P/LP variants. In group 2, 6/210 (2.86%) cases were found to have P/LP variants [5/50 in (2a) and 1/160 in (2b)].

CONCLUSION

These results show a high rate of abnormal findings on pES even in apparently normal pregnancies.

Comprehensive analysis of early pregnancy loss based on cytogenetic findings from a tertiary referral center

Background

Pregnancy loss is one of the most common complications during pregnancy. Clinical consultation based on etiology analysis are critical for reducing anxiety and distress. This study aimed to perform a comprehensive analysis for products of conception (POC) in miscarriage based on genetic etiology and clinical information.

Methods

A retrospective study was conducted according to cytogenetic findings of 1252 POC from spontaneous pregnancy loss over 11 years. The frequencies and profiles of chromosomal abnormalities were discussed according to the classification of women with different maternal ages, previous miscarriage history, normal live birth history, and different modes of conception.

Results

A total of 667 (53.2%) chromosomal abnormalities were observed, including 592 (47.3%) cases of numerical abnormalities, 38 (3.0%) cases of structural abnormalities, and 37 (3.0%) cases of mosaic aberrations. In women above 40 years of age, the rates of chromosomal abnormalities and viable autosomal trisomy were significantly higher than those in women with ≤ 29, 30–34, and 35–39 years of age (p < 0.05). The frequency of abnormal karyotype in women with normal live birth history was 61.1%, significantly higher than 52.5% in women without normal live birth history (p < 0.05). There was no significant differences among women without, with 1–2, and ≥ 3 previous miscarriages regarding the rate of abnormal karyotype (p > 0.05); viable autosomal trisomy was less common in women with ≥ 3 previous miscarriages than women with < 3 miscarriages. The frequency of chromosomal abnormalities was 49.0% and 55.0% in women with assisted conception and natural conception (p > 0.05), respectively; monosomy X was more frequently detected in women with natural conception than assisted conception.

Conclusion

The frequencies and profiles of chromosomal abnormalities in early miscarriages are strongly associated with clinical information including maternal age, previous miscarriage, live birth history, and mode of conception. Cytogenetic analysis of POC should be recommended to women with a first miscarriage and women with normal live birth history.

Exome and genome sequencing for pediatric patients with congenital anomalies or intellectual disability: an evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG)

PURPOSE

To develop an evidence-based clinical practice guideline for the use of exome and genome sequencing (ES/GS) in the care of pediatric patients with one or more congenital anomalies (CA) with onset prior to age 1 year or developmental delay (DD) or intellectual disability (ID) with onset prior to age 18 years.

METHODS

The Pediatric Exome/Genome Sequencing Evidence-Based Guideline Work Group (n = 10) used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) evidence to decision (EtD) framework based on the recent American College of Medical Genetics and Genomics (ACMG) systematic review, and an Ontario Health Technology Assessment to develop and present evidence summaries and health-care recommendations. The document underwent extensive internal and external peer review, and public comment, before approval by the ACMG Board of Directors.

RESULTS

The literature supports the clinical utility and desirable effects of ES/GS on active and long-term clinical management of patients with CA/DD/ID, and on family-focused and reproductive outcomes with relatively few harms. Compared with standard genetic testing, ES/GS has a higher diagnostic yield and may be more cost-effective when ordered early in the diagnostic evaluation.

CONCLUSION

We strongly recommend that ES/GS be considered as a first- or second-tier test for patients with CA/DD/ID.

An approach to rapid characterization of DMD copy number variants for prenatal risk assessment

Prenatal detection of structural variants of uncertain significance, including copy number variants (CNV), challenges genetic counseling, and creates ambiguity for expectant parents. In Duchenne muscular dystrophy, variant classification and phenotypic severity of CNVs are currently assessed by familial segregation, prediction of the effect on the reading frame, and precedent data. Delineation of pathogenicity by familial segregation is limited by time and suitable family members, whereas analytical tools can rapidly delineate potential consequences of variants. We identified a duplication of uncertain significance encompassing a portion of the dystrophin gene (DMD) in an unaffected mother and her male fetus. Using long-read whole genome sequencing and alignment of short reads, we rapidly defined the precise breakpoints of this variant in DMD and could provide timely counseling. The benign nature of the variant was substantiated, more slowly, by familial segregation to a healthy maternal uncle. We find long-read whole genome sequencing of clinical utility in a prenatal setting for accurate and rapid characterization of structural variants, specifically a duplication involving DMD.

Prenatal Diagnosis by Chromosome Microarray Analysis, An Indian Experience

BACKGROUND

Karyotyping has been the gold standard for prenatal chromosome analysis. The resolution should be higher by chromosome microarray analysis (CMA). The challenge lies in recognizing benign and pathogenic or clinically significant copy number variations (pCNV) and variations of unknown significance (VOUS). The aim was to evaluate the diagnostic yield and clinical utility of CMA, to stratify the CMA results in various prenatal referral groups and to accumulate Indian data of pCNVs and VOUS for further interpretation to assist defined genetic counseling.

METHODS

Karyotyping and CMA were performed on consecutive referrals of 370 prenatal samples of amniotic fluid (n = 274) and chorionic villi (n = 96) from Indian pregnant women with high maternal age (n = 23), biochemical screen positive (n = 61), previous child abnormal (n = 59), abnormal fetal ultrasound (n = 205) and heterozygous parents (n = 22).

RESULTS AND CONCLUSION

The overall diagnostic yield of abnormal results was 5.40% by karyotyping and 9.18% by CMA. The highest percentage of pCNVs were found in the group with abnormal fetal ultrasound (5.40%) as compared to other groups, such as women with high maternal age (0.81%), biochemical screen positive (0.54%), previous abnormal offspring (0.81%) or heterozygous parents group (1.62%). Therefore, all women with abnormal fetal ultrasound must undergo CMA test for genotype-phenotype correlation. CMA detects known and rare deletion/duplication syndromes and characterizes marker chromosomes. Accumulation of CNV data will form an Indian Repository and also help to resolve the uncertainty of VOUS. Pretest and posttest genetic counseling is essential to convey benefits and limitations of CMA and help the patients to take informed decisions.

Exome sequencing reveals predominantly de novo variants in disorders with intellectual disability (ID) in the founder population of Finland

The genetics of autosomal recessive intellectual disability (ARID) has mainly been studied in consanguineous families, however, founder populations may also be of interest to study intellectual disability (ID) and the contribution of ARID. Here, we used a genotype-driven approach to study the genetic landscape of ID in the founder population of Finland. A total of 39 families with syndromic and non-syndromic ID were analyzed using exome sequencing, which revealed a variant in a known ID gene in 27 families. Notably, 75% of these variants in known ID genes were de novo or suspected de novo (64% autosomal dominant; 11% X-linked) and 25% were inherited (14% autosomal recessive; 7% X-linked; and 4% autosomal dominant). A dual molecular diagnosis was suggested in two families (5%). Via additional analysis and molecular testing, we identified three cases with an abnormal molecular karyotype, including chr21q22.12q22.2 uniparental disomy with a mosaic interstitial 2.7 Mb deletion covering DYRK1A and KCNJ6. Overall, a pathogenic or likely pathogenic variant was identified in 64% (25/39) of the families. Last, we report an alternate inheritance model for 3 known ID genes (UBA7, DDX47, DHX58) and discuss potential candidate genes for ID, including SYPL1 and ERGIC3 with homozygous founder variants and de novo variants in POLR2F and DNAH3. In summary, similar to other European populations, de novo variants were the most common variants underlying ID in the studied Finnish population, with limited contribution of ARID to ID etiology, though mainly driven by founder and potential founder variation in the latter case.

CNV profiles of Chinese pediatric patients with developmental disorders

PURPOSE

To examine the overall genomic copy-number variant (CNV) landscape of Chinese pediatric patients with developmental disorders.

METHODS

De-identified chromosomal microarray (CMA) data from 10,026 pediatric patients with developmental disorders were collected for re-evaluating the pathogenic CNV (pCNV) yields of different medical conditions and for comparing the frequency and phenotypic variability of genomic disorders between the Chinese and Western patient populations.

RESULTS

The overall yield of pCNVs in the Chinese pediatric patient cohort was 21.37%, with variable yields for different disorders. Yields of pCNVs were positively associated with phenotypic complexity and intellectual disability/developmental delay (ID/DD) comorbidity for most disorders. The genomic burden and pCNV yield in neurodevelopmental disorders supported a female protective effect. However, the stratification analysis revealed that it was seen only in nonsyndromic ID/DD, not in nonsyndromic autism spectrum disorders or seizure. Furthermore, 15 known genomic disorders showed significantly different frequencies in Chinese and Western patient cohorts, and profiles of referred clinical features for 15 known genomic disorders were also significantly different in the two cohorts.

CONCLUSION

We defined the pCNV yields and profiles of the Chinese pediatric patients with different medical conditions and uncovered differences in the frequency and phenotypic diversity of genomic disorders between Chinese and Western patients.

Chromosomal microarray analysis for pregnancies with or without ultrasound abnormalities in women of advanced maternal age

BACKGROUND

Chromosomal microarray analysis (CMA) has been suggested to be routinely conducted for fetuses with ultrasound abnormalities (UA), especially with ultrasound structural anomalies (USA). Whether to routinely offer CMA to women of advanced maternal age (AMA) without UA when undergoing invasive prenatal testing is inconclusive.

OBJECTIVE

This study aimed to evaluate the efficiency of CMA in detecting clinically significant chromosomal abnormalities in fetuses, with or without UA, of women with AMA.

METHODS

Data from singleton pregnancies referred for prenatal CMA due to AMA, with or without UA were obtained. The enrolled cases were divided into AMA group (group A) and AMA accompanied by UA group (group B). Single nucleotide polymorphism (SNP) array technology and conventional karyotyping were performed simultaneously.

RESULTS

A total of 703 cases were enrolled and divided into group A (N = 437) and group B (N = 266). Clinically significant abnormalities were detected by CMA in 52 cases (7.4%, 52/703; the value in group A was significantly lower than that in group B (3.9% vs 13.2%, P < .05); no statistic difference was observed with respect to submicroscopic variants of clinical significance between the two groups (0.9% vs 2.6%, P > .05).

CONCLUSIONS

Chromosomal microarray analysis should be available to all women with AMA undergoing invasive prenatal testing, regardless of ultrasound findings.

Systematic evidence-based review: outcomes from exome and genome sequencing for pediatric patients with congenital anomalies or intellectual disability

Purpose

Exome and genome sequencing (ES/GS) are performed frequently in patients with congenital anomalies, developmental delay, or intellectual disability (CA/DD/ID), but the impact of results from ES/GS on clinical management and patient outcomes is not well characterized. A systematic evidence review (SER) can support future evidence-based guideline development for use of ES/GS in this patient population.

Methods

We undertook an SER to identify primary literature from January 2007 to March 2019 describing health, clinical, reproductive, and psychosocial outcomes resulting from ES/GS in patients with CA/DD/ID. A narrative synthesis of results was performed.

Results

We retrieved 2654 publications for full-text review from 7178 articles. Only 167 articles met our inclusion criteria, and these were primarily case reports or small case series of fewer than 20 patients. The most frequently reported outcomes from ES/GS were changes to clinical management or reproductive decision-making. Two studies reported on the reduction of mortality or morbidity or impact on quality of life following ES/GS.

Conclusion

There is evidence that ES/GS for patients with CA/DD/ID informs clinical and reproductive decision-making, which could lead to improved outcomes for patients and their family members. Further research is needed to generate evidence regarding health outcomes to inform robust guidelines regarding ES/GS in the care of patients with CA/DD/ID.

Chromosomal Aberrations in Pediatric Patients with Developmental Delay/Intellectual Disability: A Single-Center Clinical Investigation

Introduction

Chromosomal microarray analysis (CMA) has currently been considered as the first-tier genetic test for patients with developmental delay/intellectual disability (DD/ID) in many countries. In this study, we performed an extensive assessment of the value of CMA for the diagnosis of children with ID/DD in China.

Methods

A total of 633 patients diagnosed with DD/ID in West China Second University Hospital, Sichuan University, were recruited from January 2014 to March 2019. The patients were classified into 4 subgroups: isolated DD/ID, DD/ID with multiple congenital anomalies (MCA), isolated autism spectrum disorders (ASDs), and DD/ID with epilepsy. CMA was performed on Affymetrix 750K platform.

Results

Among the 633 patients, 127 cases were identified as having pathogenic copy number variations (pCNVs) with an overall positive rate of 20.06%. Of the 127 cases with abnormal results, 76 cases had 35 types of microdeletion/microduplication syndromes (59.84%) including 5 cases caused by uniparental disomy (UPD), and 18 cases had unbalanced rearrangements (14.17%) including 10 cases inherited from parental balanced translocations or pericentric inversions. The diagnostic yields of pCNVs for the subgroups of isolated DD/ID, DD/ID with MCA, isolated ASD, and DD/ID with epilepsy were 18.07% (60/332), 34.90% (52/149), 3.70% (3/81), and 16.90% (12/71), respectively. The diagnostic yield of pCNVs in DD/ID patients with MCA was significantly higher than that of the other three subgroups, and the diagnostic yield of pCNVs in isolated ASD patients was significantly lower than that of the other three subgroups (p < 0.05).

Conclusion

Microdeletion/microduplication syndromes and unbalanced rearrangements are probably the main genetic etiological factors for DD/ID. DD/ID patients with MCA have a higher rate of chromosomal aberrations. Parents of DD/ID children with submicroscopic unbalance rearrangements are more likely to have chromosome balanced translocations or pericentric inversions, which might have been missed by karyotyping. CMA can significantly improve the diagnostic rate for patients with DD/ID, which is of great value for medical management and clinical guidance for genetic counseling.

Submicroscopic aberrations of chromosome 16 in prenatal diagnosis

Background

Nearly 9.89% of chromosome 16 consists of segmental duplications, which makes it prone to non-homologous recombination. The present study aimed to investigate the incidence and perinatal characteristics of submicroscopic chromosome 16 aberrations in prenatal diagnosis.

Results

A total of 2,414 consecutive fetuses that underwent prenatal chromosomal microarray analysis (CMA) between January 2016 and December 2018 were reviewed. Submicroscopic anomalies of chromosome 16 accounted for 11.1% (15/134) of all submicroscopic anomalies detected in fetuses with normal karyotype, which was larger than the percentage of anomalies in any other chromosome. The 15 submicroscopic anomalies of chromosome 16 were identified in 14 cases; 12 of them had ultrasound abnormalities. They were classified as pathogenic (N = 7), and variants of uncertain significance (N = 8). Seven fetuses with variants of uncertain significance were ended in live-born, and the remaining were end in pregnancy termination.

Conclusion

Submicroscopic aberrations of chromosome 16 are frequent findings in prenatal diagnosis, which emphasize the challenge of genetic counseling and the value of CMA. Prenatal diagnosis should lead to long-term monitoring of children with such chromosomal abnormalities for better understanding of the phenotype of chromosome 16 microdeletion and microduplication syndromes.

Meta-analysis and multidisciplinary consensus statement: exome sequencing is a first-tier clinical diagnostic test for individuals with neurodevelopmental disorders

Purpose

For neurodevelopmental disorders (NDDs), etiological evaluation can be a diagnostic odyssey involving numerous genetic tests, underscoring the need to develop a streamlined algorithm maximizing molecular diagnostic yield for this clinical indication. Our objective was to compare the yield of exome sequencing (ES) with that of chromosomal microarray (CMA), the current first-tier test for NDDs.

Methods

We performed a PubMed scoping review and meta-analysis investigating the diagnostic yield of ES for NDDs as the basis of a consensus development conference. We defined NDD as global developmental delay, intellectual disability, and/or autism spectrum disorder. The consensus development conference included input from genetics professionals, pediatric neurologists, and developmental behavioral pediatricians.

Results

After applying strict inclusion/exclusion criteria, we identified 30 articles with data on molecular diagnostic yield in individuals with isolated NDD, or NDD plus associated conditions (such as Rett-like features). Yield of ES was 36% overall, 31% for isolated NDD, and 53% for the NDD plus associated conditions. ES yield for NDDs is markedly greater than previous studies of CMA (15–20%).

Conclusion

Our review demonstrates that ES consistently outperforms CMA for evaluation of unexplained NDDs. We propose a diagnostic algorithm placing ES at the beginning of the evaluation of unexplained NDDs.