BACKGROUND

Down syndrome or trisomy 21, the most common chromosomal disorder, results from the presence of a third copy of chromosome 21 and manifests as mild to moderate intellectual disability, growth retardation, congenital heart defects, gastrointestinal abnormalities, and characteristic facial features. Several methods have been used to screen for Down syndrome in the prenatal period, such as ultrasound, biomarkers, cell-free DNA testing, and combinations of these tests. A positive result from one or more of these screening tests signals the need for confirmatory karyotyping to clinch the diagnosis. Ultrasound between 11 to 14 weeks of gestation can evaluate nuchal translucency (NT) to screen for Down syndrome. During the second trimester, a triple or quadruple test can also be performed alone or in addition to NT to quantify Down syndrome risk. In limited resource settings however, only the measurement of NT via ultrasound can be performed since biomarker tests are either unavailable or inaccessible. While the diagnostic performance of NT measurement alone has been investigated in several observational studies, there is no consensus on its performance as a sole test to screen for Down syndrome.

To determine the diagnostic performance of NT during prenatal first-trimester ultrasound as a screening test for Down syndrome.

We performed a systematic search on the PubMed, ProQuest, and Cochrane Library databases for recent systematic reviews and meta-analyses that addressed the objective. The existing reviews found were then independently appraised by the two reviewers with the AMSTAR-2 checklist. To update the existing reviews, a systematic search was done in the same databases to identify additional primary diagnostic studies, which were appraised using the QUADAS-2 tool. Random-effects univariate meta-analysis and summary receiving operator curve (HSROC) analysis for the outcomes were performed using Review Manager version 5.4 and R version 4.2.2, respectively. Subgroup analysis was performed by stratifying the baseline risk of mothers for fetal anomaly as low- or high-risk. Highrisk mothers were defined as women with risk factors such as advanced age, positive serum screen, presence of other ultrasound anomalies, and history of previous fetus with anomaly.

We found 22 cohort studies (n=225,846) of women at low-risk for fetal anomaly. The pooled sensitivity was 67.8% (95% CI: 61.4%-73.6%, I2=70.4%) and specificity was 96.3% (95% CI: 95.5%-96.9%, I2=96.7%). For low-risk women, the overall certainty of evidence was low, due to different modes of verification and heterogeneity not completely explained by variability in baseline risk or cut-points. Seven studies (n=9,197) were on high-risk women. The pooled sensitivity was 62.2% (95% CI: 54.1%-69.7%, I2=38.8%) and specificity was 96.5% (95% CI: 93.6%-98.1%, I2=95.5%). For women at high-risk, the evidence was rated as moderate due to differential verification.

Our analysis showed that NT measured through first-trimester ultrasound is specific for Down syndrome but has low sensitivity. Despite this, it is a useful screening test for Down syndrome in low-resource settings where other strategies may not be available or accessible. Furthermore, interpretation of NT results must take into consideration its limited sensitivity as this may lead to missed cases.

Here, we report a previously unrecognized syndromic neurodevelopmental disorder associated with biallelic loss-of-function variants in the RBM42 gene. The patient is a 2-year-old female with severe central nervous system (CNS) abnormalities, hypotonia, hearing loss, congenital heart defects, and dysmorphic facial features. Familial whole-exome sequencing (WES) reveals that the patient has two compound heterozygous variants, c.304C>T (p.R102*) and c.1312G>A (p.A438T), in the RBM42 gene which encodes an integral component of splicing complex in the RNA-binding motif protein family. The p.A438T variant is in the RRM domain which impairs RBM42 protein stability in vivo. Additionally, p.A438T disrupts the interaction of RBM42 with hnRNP K, which is the causative gene for Au-Kline syndrome with overlapping disease characteristics seen in the index patient. The human R102* or A438T mutant protein failed to fully rescue the growth defects of RBM42 ortholog knockout ΔFgRbp1 in Fusarium while it was rescued by the wild-type (WT) human RBM42. A mouse model carrying Rbm42 compound heterozygous variants, c.280C>T (p.Q94*) and c.1306_1308delinsACA (p.A436T), demonstrated gross fetal developmental defects and most of the double mutant animals died by E13.5. RNA-seq data confirmed that Rbm42 was involved in neurological and myocardial functions with an essential role in alternative splicing (AS). Overall, we present clinical, genetic, and functional data to demonstrate that defects in RBM42 constitute the underlying etiology of a new neurodevelopmental disease which links the dysregulation of global AS to abnormal embryonic development.
Female ; Animals ; Mice ; Humans ; Child, Preschool ; Intellectual Disability/genetics* ; Heart Defects, Congenital/genetics* ; Facies ; Cleft Palate ; Muscle Hypotonia

Objective: To review the clinical data of 7 patients with Danon disease and analyze their clinical characteristics. Methods: The medical records of 7 patients with Danon disease, who were hospitalized in Peking Union Medical College Hospital of Chinese Academy of Medical Sciences from April 2008 to July 2021, were reviewed and summarized, of which 6 cases were diagnosed as Danon disease by lysosomal-associated membrane protein-2 (LAMP-2) gene mutation detection and 1 case was diagnosed by clinicopathological features. Clinical manifestations, biochemical indexes, electrocardiogram, echocardiography, skeletal muscle and myocardial biopsy and gene detection results were analyzed, and patients received clinical follow-up after discharge. Results: Six patients were male and average age was (15.4±3.5) years and the average follow-up time was (27.7±17.0) months. The main clinical manifestations were myocardial hypertrophy (6/7), decreased myodynamia (2/7) and poor academic performance (3/7). Electrocardiogram features included pre-excitation syndrome (6/7) and left ventricular hypertrophy (7/7). Echocardiography examination evidenced myocardial hypertrophy (6/7), and left ventricular dilatation and systolic dysfunction during the disease course (1/7). The results of skeletal muscle biopsy in 6 patients were consistent with autophagy vacuolar myopathy. Subendocardial myocardial biopsy was performed in 3 patients, and a large amount of glycogen deposition with autophagosome formation was found in cardiomyocytes. LAMP-2 gene was detected in 6 patients, and missense mutations were found in all these patients. During the follow-up period, implantable cardioverter defibrillator implantation was performed in 1 patient because of high atrioventricular block 4 years after diagnosis, and there was no death or hospitalization for cardiovascular events in the other patients. Conclusion: The main clinical manifestations of Danon disease are cardiomyopathy, myopathy and mental retardation. Pre-excitation syndrome is a common electrocardiographic manifestation. Autophagy vacuoles can be seen in skeletal muscle and myocardial pathological biopsies. LAMP-2 gene mutation analysis is helpful in the diagnose of this disease.
Adolescent ; Child ; Female ; Humans ; Male ; Cardiomyopathies/etiology* ; Glycogen Storage Disease Type IIb/complications* ; Hypertrophy, Left Ventricular/etiology* ; Lysosomal-Associated Membrane Protein 2/genetics* ; Pre-Excitation Syndromes/genetics*

Objective: To investigate the clinical features and gene variation characteristics of children with dynein cytoplasmic 1 heavy chain 1 (DYNC1H1) gene associated spinal muscular atrophy with lower extremity predominant (SMALED) 1. Methods: The clinical data of 4 SMALED1 children admitted to Peking University First Hospital from December 2018 to May 2021, who were found to have pathogenic variation of DYNC1H1 gene through genetic testing, except for other genes known to be related to motor retardation, were retrospectively summarized to analyze the phenotype and genotype characteristics. Results: There were 3 males and 1 female. The age of onset was 1 year, 1 day, 1 day and 4 months, respectively. The age of diagnosis was 4 years and 10 months, 9 months, 5 years and 9 months, and 3 years and 1 month, respectively. The clinical manifestations were muscle weakness and muscular atrophy of lower limbs, 2 cases with foot deformity, 1 case with early non progressive joint contracture, 1 case with hip dislocation and 1 case with mental retardation. De novo heterozygous missense variations in DYNC1H1 gene were found in all 4 children. According to the rating of American College of medical genetics and genomics, they were all possible pathogenic and pathogenic variations, with p.R598C, p.P776L, p.Y1109D variations had been reported, and p.I1086R variation had not been reported. Conclusions: For those with unexplained lower limb muscle weakness, muscle atrophy, joint contracture and foot deformity, upper limb motor ability related retention, with or without mental retardation, as well as the motor ability progresses slowly, it is necessary to consider the possibility of SMALED1 and the detection of DYNC1H1 gene when necessary.
Female ; Male ; Humans ; Intellectual Disability ; Retrospective Studies ; Muscular Atrophy, Spinal/genetics* ; Lower Extremity ; Muscle Weakness ; Muscular Atrophy ; Contracture ; Cytoplasmic Dyneins/genetics*

Humans ; Prader-Willi Syndrome/therapy*

OBJECTIVE: To explore the clinical and genetic characteristics of three children with KBG syndrome. METHODS: Clinical data of the three children from two families who have presented at the First Affiliated Hospital of Zhengzhou University between October 2019 and September 2020 and their family members were collected. Trio-whole exome sequencing (trio-WES) and Sanger sequencing were carried out. RESULTS: All children had feeding difficulties, congenital heart defects and facial dysmorphism. The sib- pair from family 1 was found to harbor a novel de novo heterozygous c.6270delT (p.Q2091Rfs*84) variant of the ANKRD11 gene, whilst the child from family 2 was found to harbor a novel heterozygous c.6858delC (p.D2286Efs*51) variant of the ANKRD11 gene, which was inherited from his mother who had a mild clinical phenotype. CONCLUSION The heterozygous frameshift variants of the ANKRD11 gene probably underlay the disease in the three children. Above findings have enriched the spectrum of the ANKRD11 gene variants.
Female ; Child ; Humans ; Abnormalities, Multiple/genetics* ; Intellectual Disability/genetics* ; Bone Diseases, Developmental/genetics* ; Tooth Abnormalities/genetics* ; Facies ; Repressor Proteins/genetics* ; Mothers ; Mutation

OBJECTIVE: To explore the genetic basis for two patients from a family with BCL11A-related intellectual disability (BCL11A-ID). METHODS: Clinical data of the proband and her family members was analyzed. Chromosomal karyotyping analysis, trio-whole exome sequencing (trio-WES) and copy number variation sequencing (CNV-seq) were carried out. For the suspected genetic variants, Sanger sequencing was used to verify, and pathogenicity assessment was conducted. RESULTS: The proband and her mother both had intellectual and language impairment, and their fetal hemoglobin (HbF) was significantly elevated. A heterozygous c.1327_c.1328delTC (p.Ser443Hisfs*128) variant was found in exon 4 of the BCL11A gene by WES, which has resulted in truncated expression of the encoded protein, and Sanger sequencing has verified that the variant was inherited from the mother. The variant was not found in related databases. The variant was predicted as pathogenic according to the guidelines from the American College of Medical Genetics and Genomics (ACMG) (PVS1+PM2+PP1). No karyotypic abnormality was found in the proband, her parents and brother, and no pathogenic CNVs was found in the proband and her parents. CONCLUSION The c.1327_c.1328delTC (p.Ser443Hisfs*128) variant may underlay the BCL11A-ID in the proband and her mother. This de novo variant has expanded the mutational spectrum of the BCL11A gene.
Humans ; Male ; Female ; Intellectual Disability/genetics* ; DNA Copy Number Variations ; Pedigree ; Mutation ; Transcription Factors/genetics* ; Mothers ; Repressor Proteins/genetics*

OBJECTIVE: To explore the clinical and genetic features of a child with autosomal dominant mental retardation type 40 (MRD40) due to variant of the CHAMP1 gene. METHODS: Clinical characteristics of the child were analyzed. Genetic testing was carried out by low-depth high-throughput and whole genome copy number variant sequencing (CNV-seq) and whole exome sequencing (WES). A literature review was also carried out for the clinical phenotype and genetic characteristics of patients with MRD40 due to CHAMP1 gene variants. RESULTS: The child, a 11-month-old girl, has presented with intellectual and motor developmental delay. CNV-seq revealed no definite pathogenic variants. WES has detected the presence of a heterozygous c.1908C>G (p.Y636*) variant in the CHAMP1 gene, which was carried by neither parent and predicted to be pathogenic. Literature review has identified 33 additional children from 12 previous reports. All children had presented with developmental delay and mental retardation, and most had dystonia (94.1%), delayed speech and/or walking (85.2%, 82.4%) and ocular abnormalities (79.4%). In total 26 variants of the CHAMP1 gene were detected, with all nonsense variants being of loss-of-function type, located in exon 3, and de novo in origin. CONCLUSION The heterozygous c.1908C>G (p.Y636*) variant of the CHAMP1 gene probably underlay the WRD40 in this child. Genetic testing should be considered for children featuring global developmental delay, mental retardation, hypertonia and facial dysmorphism.
Humans ; Intellectual Disability/genetics* ; Genetic Testing ; Phenotype ; Exome Sequencing ; Heterozygote ; Mutation ; Chromosomal Proteins, Non-Histone/genetics* ; Phosphoproteins/genetics*

OBJECTIVE: To explore the genetic basis for a child with mental retardation. METHODS: Whole exome sequencing was carried out for the child. Candidate variant was screened based on his clinical features and verified by Sanger sequencing. RESULTS: The child was found to harbor a c.995_1002delAGACAAAA(p.Asp332AlafsTer84) frameshift variant in the SYNGAP1 gene. Bioinformatic analysis suggested it to be pathogenic. The same variant was not detected in either parent. CONCLUSION The c.995_1002delAGACAAAA(p.Asp332AlafsTer84) frameshift variant of the SYNGAP1 gene probably underlay the mental retardation in this child. Above finding has expanded the spectrum of SYNGAP1 gene variants and provided a basis for the diagnosis and treatment for this child.
Child ; Humans ; Intellectual Disability/genetics* ; Frameshift Mutation ; High-Throughput Nucleotide Sequencing ; Computational Biology ; Heterozygote ; Mutation ; ras GTPase-Activating Proteins/genetics*

OBJECTIVE: To explore the genetic etiology for a child featuring mental retardation, language delay and autism. METHODS: G-banding chromosomal karyotyping and single nucleotide polymorphism array (SNP-array) were carried out for the child and her parents. RESULTS: The child was found to have a 46,XX,dup(8p?) karyotype, for which both of her parents were normal. SNP-array revealed that the child has harbored a 6.8 Mb deletion in 8p23.3p23.1 and a 21.8 Mb duplication in 8p23.1p12, both of which were verified as de novo pathogenic copy number variants. CONCLUSION The clinical features of the child may be attributed to the 8p deletion and duplication. SNP-array can facilitate genetic diagnosis for children featuring mental retardation in conjunct with other developmental anomalies.
Humans ; Child ; Pregnancy ; Female ; Intellectual Disability/genetics* ; Prenatal Diagnosis ; Karyotyping ; Chromosome Banding ; Chromosome Deletion