Genetic tests by next-generation sequencing in children with developmental delay and/or intellectual disability

Reverse Phenotyping after Whole-Exome Sequencing in Children with Developmental Delay/Intellectual Disability-An Exception or a Necessity?

This study delves into the diagnostic yield of whole-exome sequencing (WES) in pediatric patients presenting with developmental delay/intellectual disability (DD/ID), while also exploring the utility of Reverse Phenotyping (RP) in refining diagnoses. A cohort of 100 pediatric patients underwent WES, yielding a diagnosis in 66% of cases. Notably, RP played a significant role in cases with negative prior genetic testing, underscoring its significance in complex diagnostic scenarios. The study revealed a spectrum of genetic conditions contributing to DD/ID, illustrating the heterogeneity of etiological factors. Despite challenges, WES demonstrated effectiveness, particularly in cases with metabolic abnormalities. Reverse phenotyping was indicated in half of the patients with positive WES findings. Neural network models exhibited moderate-to-exceptional predictive abilities for aiding in patient selection for WES and RP. These findings emphasize the importance of employing comprehensive genetic approaches and RP in unraveling the genetic underpinnings of DD/ID, thereby facilitating personalized management and genetic counseling for affected individuals and families. This research contributes insights into the genetic landscape of DD/ID, enhancing our understanding and guiding clinical practice in this particular field of clinical genetics.

Clinical profiles and molecular genetic analyses of 98 Chinese children with short statures

Background

Short stature is one of the most prevalent endocrine disorders in children, and its genetic basis is a complex and actively researched subject. Currently, there is limited genetic research on exome sequencing for short stature, and more large-scale studies are necessary for further exploration.

Methods

The retrospective study entailed investigation of 98 Chinese children with short statures (height SDS ≤ -2.5) of unknown etiologies recruited between 2017 and 2021. Whole-exome sequencing (WES) was performed on these patients to identify the potential genetic etiologies. The clinical data were reviewed retrospectively to assess the pathogenicity of the identified mutations. Additionally, 31 patients consented to and received recombinant human growth hormone (rhGH) therapy for 12 months. The short-term effects of rhGH treatment were evaluated across different etiologies of patients with short statures.

Results

The WES results were used to identify 31 different variants in 18 genes among 24 (24.5%) patients. Individuals with more severe short statures were more likely to have underlying genetic etiologies. Short stature accompanied by other phenotypes had significantly higher diagnostic yields than simple severe short stature. The rhGH therapy demonstrated efficacy in most children. Nevertheless, the treatment response was suboptimal in a boy diagnosed with 3M syndrome.

Conclusion

WES is an important approach for confirming genetic disorders in patients with severe short statures of unknown etiologies, suggesting that it could be used as a primary diagnostic strategy. The administration of rhGH may not be suitable for all children with short statures, and the identification of the genetic cause of short stature by WES has significant guidance value for rhGH treatment.

Molecular pathways and therapeutic strategies in dermatofibrosarcoma protuberans (DFSP): unravelling the tumor's genetic landscape

Dermatofibrosarcoma Protuberans (DFSP) is a rare soft tissue sarcoma distinguished by its infiltrative growth pattern and recurrence potential. Understanding the molecular characteristics of DFSP is essential for enhancing its diagnosis, prognosis, and treatment strategies. The paper provides an overview of DFSP, highlighting the significance of its molecular understanding. The gene expression profiling has uncovered unique molecular signatures in DFSP, highlighting its heterogeneity and potential therapeutic targets. The Platelet-Derived Growth Factor Receptors (PDGFRs) and Fibroblast Growth Factor Receptors (FGFRs) signaling pathways play essential roles in the progression and development of DFSP. The abnormal activation of these pathways presents opportunities for therapeutic interventions. Several emerging therapies, i.e., immunotherapies, immunomodulatory strategies, and immune checkpoint inhibitors, offer promising alternatives to surgical resection. In DFSP management, combination strategies, including rational combination therapies, aim to exploit the synergistic effects and overcome resistance. The article consisting future perspectives and challenges includes the discovery of prognostic and predictive biomarkers to improve risk stratification and treatment selection. Preclinical models, such as Patient-derived xenografts (PDX) and genetically engineered mouse models, help study the biology of DFSP and evaluate therapeutic interventions. The manuscript also covers small-molecule inhibitors, clinical trials, immune checkpoint inhibitors for DFSP treatment, combination therapies, rational therapies, and resistance mechanisms, which are unique and not broadly covered in recent pieces of literature. See also the graphical abstract(Fig. 1).

Clinical application of prospective whole-exome sequencing in the diagnosis of genetic disease: Experience of a regional disease center in South Korea

INTRODUCTION

Next-generation sequencing helps clinicians diagnose patients with suspected genetic disorders. The current study aimed to investigate the diagnostic yield and clinical utility of prospective whole-exome sequencing (WES) in rare diseases.

METHODS

WES was performed in 92 patients who presented with clinical symptoms suggestive of genetic disorders. The WES data were analyzed using an in-house developed software. The patients' phenotypic characteristics were classified according to the human phenotype ontology.

RESULTS

WES detected 64 variants, 13 were classified as pathogenic, 26 as likely pathogenic, and 25 as variants of uncertain significance. In 57 patients with these variants, 30 were identified as causal variants. The diagnostic yield was higher in patients with abnormalities in joint mobility and skin morphology than in those with cerebellar hypoplasia/atrophy, epilepsy, global developmental delay, dysmorphic features/facial dysmorphisms, and chronic kidney disease/abnormal renal morphology.

CONCLUSION

In this study, a WES-based variant interpretation system was employed to provide a definitive diagnosis for 28.3% of the patients suspected of having genetic disorders. WES is particularly useful for diagnosing rare diseases with symptoms that affect more than one system, when targeted genetic panels are difficult to employ.

Clinical use of whole exome sequencing in children with developmental delay/intellectual disability

BACKGROUND

Identifying the underlying etiology of developmental delay/intellectual disability (DD/ID) is challenging but important. The genetic diagnosis of unexplained DD/ID helps in the treatment and prognosis of the disability in patients. In this study, we reported our experience of using whole exome sequencing (WES) of children with unexplained DD/ID.

METHODS

We conducted a retrospective analysis of WES results of children under 19 years of age with unexplained DD/ID between January 2020 and December 2021. The demographic data of all patients and variants identified through WES were evaluated. Furthermore, we evaluated the clinical characteristics that influenced the identification of genetic causes.

RESULTS

Forty-one patients with DD/ID were included, of whom 21 (51.2 %) were male. The average age at symptom onset was 1.6 ± 1.3 years, and the duration from symptom onset to diagnosis was 3.1 ± 3.7 years. Hypotonia was the most common symptom (17 patients, 41.5 %), and epilepsy was confirmed in 10 patients (24.4 %). Twenty-two pathogenic/likely pathogenic variants were identified in 20 patients, and three variants of uncertain significance were identified in three patients. Family-based trio Sanger sequencing for candidate variants of 12 families was conducted; 10 variants were de novo, one variant paternally inherited, and two variants compound heterozygous. The diagnostic yield of WES for DD/ID was 48.8 % and was significantly high in patients with an early onset of DD/ID and facial dysmorphism. In contrast, patients with autism spectrum disorder (ASD) were more likely to have negative WES results compared with others without ASD.

CONCLUSION

The diagnostic yield of WES was 48.8 %. We conclude that patients' characteristics, such as dysmorphic features and the age of symptom onset, can predict the likelihood that WES will identify a causal variant of a phenotype.

A novel heterozygous ZBTB18 missense mutation in a family with non-syndromic intellectual disability

Intellectual disability (ID) is a common neurodevelopmental disorder characterized by significantly impaired adaptive behavior and cognitive capacity. High throughput sequencing approaches have revealed the genetic etiologies for 25-50% of ID patients, while inherited genetic mutations were detected in <5% cases. Here, we investigated the genetic cause for non-syndromic ID in a Han Chinese family. Whole genome sequencing was performed on identical twin sisters diagnosed with ID, their respective children, and their asymptomatic parents. Data was filtered for rare variants, and in silico prediction tools were used to establish pathogenic alleles. Candidate mutations were validated by Sanger sequencing. In silico modeling was used to evaluate the mutation's effects on the protein encoded by a candidate coding gene. A novel heterozygous variant in the ZBTB18 gene c.1323C>G (p.His441Gln) was identified. This variant co-segregated with affected individuals in an autosomal dominant pattern and was not detected in asymptomatic family members. Molecular studies reveal that a p.His441Gln substitution disrupts zinc binding within the second zinc finger and disrupts the capacity for ZBTB18 to bind DNA. This is the first report of an inherited ZBTB18 mutation for ID. This study further validates WGS for the accurate molecular diagnosis of ID.

Loss of function of ADNP by an intragenic inversion

ADNP is a well-known gene implicated in intellectual disability and its molecular spectrum consists mainly in loss of function variant in the ADNP last and largest exon. Here, we report the first description of a patient with intellectual disability identified with an intragenic inversion in ADNP. RNAseq experiment showed a splice skipping of the inversed exons. Moreover, in-silico analysis of initiating ATGs in the mutated transcript using contextual Kozak score suggested that several initiating ATGs were likely used to translate poisonous out-of-frame ORFs and would lead to the suppression of any in-frame rescuing translation, thereby causing haploinsufficiency. As constitutive Alu sequences with high homology were identified at both breakpoints in reversed orientation in the reference genome, we hypothesized that Alu-mediated non-allelic-homologous recombination was responsible for this rearrangement. Therefore, as this inversion is not detectable by exome sequencing, this mechanism could be a potential underdiagnosed recurrent mutation in ADNP-related disorders.

Phenotypic specificity in patients with neurodevelopmental delay does not correlate with diagnostic yield of trio-exome sequencing

In this study, we aimed to examine the diagnostic yield achieved by applying a trio approach in exome sequencing (ES) and the interdependency between the clinical specificity in families with neurodevelopmental delay. Thirty-seven families were recruited and trio-ES as well as three criteria for estimating the clinical phenotypic specificity were suggested and applied to the underaged children. All our patients showed neurodevelopmental delay and most of them a large spectrum of congenital anomalies. Applying the pathogenicity guidelines of the American College of Medical Genetics (ACMG), likely pathogenic (29.7%) and pathogenic variants (8.1%) were found in 40,5% of our index patients. Additionally, we found four variants of uncertain significance (VUS; according to ACMG) and two genes of interest (GOI; going beyond ACMG classification) (GLRA4, NRXN2). Spastic Paraplegia 4 (SPG4) caused by a formerly known SPAST variant was diagnosed in a patient with a complex phenotype, in whom a second genetic disorder may be present. A potential pathogenic variant linked to severe intellectual disability in GLRA4 requires further investigation. No interdependency between the diagnostic yield and the clinical specificity of the phenotypes could be observed. In consequence, trio-ES should be used early in the diagnostic process, independently from the specificity of the patient.

High Performance of a Dominant/X-Linked Gene Panel in Patients with Neurodevelopmental Disorders

Neurodevelopmental disorders (NDDs) affect 2–5% of the population and approximately 50% of cases are due to genetic factors. Since de novo pathogenic variants account for the majority of cases, a gene panel including 460 dominant and X-linked genes was designed and applied to 398 patients affected by intellectual disability (ID)/global developmental delay (GDD) and/or autism (ASD). Pathogenic variants were identified in 83 different genes showing the high genetic heterogeneity of NDDs. A molecular diagnosis was established in 28.6% of patients after high-depth sequencing and stringent variant filtering. Compared to other available gene panel solutions for NDD molecular diagnosis, our panel has a higher diagnostic yield for both ID/GDD and ASD. As reported previously, a significantly higher diagnostic yield was observed: (i) in patients affected by ID/GDD compared to those affected only by ASD, and (ii) in females despite the higher proportion of males among our patients. No differences in diagnostic rates were found between patients affected by different levels of ID severity. Interestingly, patients harboring pathogenic variants presented different phenotypic features, suggesting that deep phenotypic profiling may help in predicting the presence of a pathogenic variant. Despite the high performance of our panel, whole exome-sequencing (WES) approaches may represent a more robust solution. For this reason, we propose the list of genes included in our customized gene panel and the variant filtering procedure presented here as a first-tier approach for the molecular diagnosis of NDDs in WES studies.

Whole-Exome Sequencing of Pakistani Consanguineous Families Identified Pathogenic Variants in Genes of Intellectual Disability

Intellectual disability (ID) is a condition of significant limitation of cognitive functioning and adaptive behavior, with 50% of etiology attributed to genetic predisposition. We recruited two consanguineous Pakistani families manifesting severe ID and developmental delay. The probands were subjected to whole exome sequencing (WES) and variants were further prioritized based on population frequency, predicted pathogenicity and functional relevance. The WES data analysis identified homozygous pathogenic variants in genes MBOAT7 and TRAPPC9. The pathogenicity of the variants was supported by co-segregation analysis and in silico tool. The findings of this study expand mutation spectrum and provide additional evidence to the role of MBOAT7 and TRAPPC9 in causation of ID.

Pitfalls of whole exome sequencing in undefined clinical conditions with a suspected genetic etiology

BACKGROUND

Whole-Exome Sequencing (WES) is a valuable tool for the molecular diagnosis of patients with a suspected genetic condition. In complex and heterogeneous diseases, the interpretation of WES variants is more challenging given the absence of diagnostic handles and other reported cases with overlapping clinical presentations.

OBJECTIVE

To describe candidate variants emerging from trio-WES and possibly associated with the clinical phenotype in clinically heterogeneous conditions.

METHODS

We performed WES in ten patients from eight families, selected because of the lack of a clear clinical diagnosis or suspicion, the presence of multiple clinical signs, and the negative results of traditional genetic tests.

RESULTS

Although we identified ten candidate variants, reaching the diagnosis of these cases is challenging, given the complexity and the rarity of these syndromes and because affected genes are already associated with known genetic diseases only partially recapitulating patients' phenotypes. However, the identification of these variants could shed light into the definition of new genotype-phenotype correlations. Here, we describe the clinical and molecular data of these cases with the aim of favoring the match with other similar cases and, hopefully, confirm our diagnostic hypotheses.

CONCLUSION

This study emphasizes the major limitations associated with WES data interpretation, but also highlights its clinical utility in unraveling novel genotype-phenotype correlations in complex and heterogeneous undefined clinical conditions with a suspected genetic etiology.

Unearthing novel fusions as therapeutic targets in solid tumors using targeted RNA sequencing

Detection of oncogenic fusion genes in cancers, particularly in the diagnosis of uncertain tumors, is crucial for determining effective therapeutic strategies. Although novel fusion genes have been discovered through sequencing, verifying their oncogenic potential remain difficult. Therefore, we evaluated the utility of targeted RNA sequencing in 165 tumor samples by identifying known and unknown fusions. Additionally, by applying additional criteria, we discovered eight novel fusion genes that are expected to process oncogenicity. Among the novel fusion genes, RAF1 fusion genes were detected in two cases. PTPRG-RAF1 fusion led to an increase in cell growth; while dabrafenib, a BRAF inhibitor, reduced the growth of cells expressing RAF1. This study demonstrated the utility of RNA panel sequencing as a theragnostic tool and established criteria for identifying oncogenic fusion genes during post-sequencing analysis.

Pathogenic KDM5B variants in the context of developmental disorders

Histone modifying enzymes are involved in the posttranslational modification of histones and the epigenetic control of gene expression. They play a critical role in normal development, and there is increasing evidence of their role in developmental disorders (DDs). DDs are a group of chronic, severe conditions that impact the physical, intellectual, language and/or behavioral development of an individual. There are very few treatment options available for DDs such that these are conditions with significant unmet clinical need. Recessive variants in the gene encoding histone modifying enzyme KDM5B are associated with a DD characterized by developmental delay, facial dysmorphism and camptodactyly. KDM5B is responsible for the demethylation of lysine 4 on the amino tail of histone 3 and plays a vital role in normal development and regulating cell differentiation. This review explores the literature on KDM5B and what is currently known about its roles in development and developmental disorders.

Diagnostic yield of patients with undiagnosed intellectual disability, global developmental delay and multiples congenital anomalies using karyotype, microarray analysis, whole exome sequencing from Central Brazil

Intellectual Disability (ID) is a neurodevelopmental disorder that affects approximately 3% of children and adolescents worldwide. It is a heterogeneous and multifactorial clinical condition. Several methodologies have been used to identify the genetic causes of ID and in recent years new generation sequencing techniques, such as exome sequencing, have enabled an increase in the detection of new pathogenic variants and new genes associated with ID. The aim of this study was to evaluate exome sequencing with analysis of the ID gene panel as a tool to increase the diagnostic yield of patients with ID/GDD/MCA in Central Brazil, together with karyotype and CMA tests. A retrospective cohort study was carried out with 369 patients encompassing both sexes. Karyotype analysis was performed for all patients. CMA was performed for patients who did not present structural and or numerical alterations in the karyotype. Cases that were not diagnosed after performing karyotyping and CMA were referred for exome sequencing using a gene panel for ID that included 1,252 genes. The karyotype identified chromosomal alterations in 34.7% (128/369). CMA was performed in 83 patients who had normal karyotype results resulting in a diagnostic yield of 21.7% (18/83). Exome sequencing with analysis of the ID gene panel was performed in 19 trios of families that had negative results with previous methodologies. With the ID gene panel analysis, we identified mutations in 63.1% (12/19) of the cases of which 75% (9/12) were pathogenic variants,8.3% (1/12) likely pathogenic and in 16.7% (2/12) it concerned a Variant of Uncertain Significance. With the three methodologies applied, it was possible to identify the genetic cause of ID in 42.3% (156/369) of the patients. In conclusion, our studies show the different methodologies that can be useful in diagnosing ID/GDD/MCA and that whole exome sequencing followed by gene panel analysis, when combined with clinical and laboratory screening, is an efficient diagnostic strategy.

Clinical Profiles and Genetic Spectra of 814 Chinese Children With Short Stature

CONTEXT

Data and studies based on exome sequencing for the genetic evaluation of short stature are limited, and more large-scale studies are warranted. Some factors increase the likelihood of a monogenic cause of short stature, including skeletal dysplasia, severe short stature, and small for gestational age (SGA) without catch-up growth. However, whether these factors can serve as predictors of molecular diagnosis remains unknown.

OBJECTIVE

We aimed to explore the diagnostic efficiency of the associated risk factors and their exome sequences for screening.

METHODS

We defined and applied factors that increased the likelihood of monogenic causes of short stature in diagnostic genetic tests based on next-generation sequencing (NGS) in 814 patients with short stature and at least 1 other factor.

RESULTS

Pathogenic/likely pathogenic (P/LP) variants in genes, copy number variations, and chromosomal abnormalities were identified in 361 patients. We found P/LP variants among 111 genes, and RASopathies comprised the most important etiology. Short stature combined with other phenotypes significantly increased the likelihood of a monogenic cause, including skeletal dysplasia, facial dysmorphism, and intellectual disability, compared with simple severe short stature (<-3 SD scores). We report novel candidate pathogenic genes, KMT2C for unequivocal growth hormone insensitivity and GATA6 for SGA.

CONCLUSION

Our study identified the diagnostic characteristics of NGS in short stature with different risk factors. Our study provides novel insights into the current understanding of the etiology of short stature in patients with different phenotypes.

Genome Sequencing for Genetics Diagnosis of Patients With Intellectual Disability: The DEFIDIAG Study

Introduction: Intellectual Disability (ID) is the most common cause of referral to pediatric genetic centers, as it affects around 1–3% of the general population and is characterized by a wide genetic heterogeneity. The Genome Sequencing (GS) approach is expected to achieve a higher diagnostic yield than exome sequencing given its wider and more homogenous coverage, and, since theoretically, it can more accurately detect variations in regions traditionally not well captured and identify structural variants, or intergenic/deep intronic putatively pathological events. The decreasing cost of sequencing, the progress in data-management and bioinformatics, prompted us to assess GS efficiency as the first line procedure to identify the molecular diagnosis in patients without obvious ID etiology. This work is being carried out in the framework of the national French initiative for genomic medicine (Plan France Médecine Génomique 2025).

Methods and Analysis: This multidisciplinary, prospective diagnostic study will compare the diagnostic yield of GS trio analysis (index case, father, mother) with the French core minimal reference strategy (Fragile-X testing, chromosomal microarray analysis and Gene Panel Strategy of 44 selected ID genes). Both strategies are applied in a blinded fashion, in parallel, in the same population of 1275 ID index cases with no obvious diagnosis (50% not previously investigated). Among them, a subgroup of 196 patients are randomized to undergo GS proband analysis in addition to GS trio analysis plus the French core minimal reference strategy, in order to compare their efficiency. The study also aims to identify the most appropriate strategy according to the clinical presentation of the patients, to evaluate the impact of deployment of GS on the families’ diagnostic odyssey and the modification of their care, and to identify the advantages/difficulties for the patients and their families.

Ethics Statement: The protocol was approved by the Ethics Committee Sud Méditerranée I and the French data privacy commission (CNIL, authorization 919361).

Trial Registration:ClinicalTrials.gov identifier NCT04154891 (07/11/2019).

Exome sequencing vs targeted gene panels for the evaluation of nonimmune hydrops fetalis

BACKGROUND

Next-generation sequencing is increasingly used in prenatal diagnosis. Targeted gene panels and exome sequencing are both available, but the comparative diagnostic yields of these approaches are not known.

OBJECTIVE

We compared the diagnostic yield of exome sequencing with the simulated application of commercial targeted gene panels in a large cohort of fetuses with nonimmune hydrops fetalis.

STUDY DESIGN

This was a secondary analysis of a cohort study of exome sequencing for nonimmune hydrops fetalis, in which recruitment, exome sequencing, and phenotype-driven variant analysis were completed in 127 pregnancies with features of nonimmune hydrops fetalis. An Internet search was performed to identify commercial laboratories that offer targeted gene panels for the prenatal evaluation of nonimmune hydrops fetalis or for specific disorders associated with nonimmune hydrops fetalis using the terms "non-immune hydrops fetalis," "fetal non-immune hydrops," "hydrops," "cystic hygroma," "lysosomal storage disease," "metabolic disorder," "inborn error of metabolism," "RASopathy," and "Noonan." Our primary outcome was the proportion of all genetic variants identified through exome sequencing that would have been identified if a targeted gene panel had instead been used. The secondary outcomes were the proportion of genetic variants that would have been identified by type of targeted gene panel (general nonimmune hydrops fetalis, RASopathy, or metabolic) and the percent of variants of uncertain significance that would have been identified on the panels, assuming 100% analytical sensitivity and specificity of panels for variants in the included genes.

RESULTS

Exome sequencing identified a pathogenic or likely pathogenic variant in 37 of 127 cases (29%) in a total of 29 genes. A variant of uncertain significance, strongly suspected to be associated with the phenotype, was identified in another 12 cases (9%). We identified 7 laboratories that offer 10 relevant targeted gene panels; 6 are described as RASopathy panels, 3 as nonimmune hydrops fetalis panels, and 1 as a metabolic panel. The median number of genes included on each of these panels is 22, ranging from 11 to 148. Had a nonimmune hydrops fetalis targeted gene panel been used instead of exome sequencing, 13 to 15 of the 29 genes (45%-52%) identified in our nonimmune hydrops fetalis cohort would have been sequenced, and 19 to 24 of the pathogenic variants (51%-62%) would have been detected. The yield was predicted to be the lowest with the metabolic panel (11%) and the highest with the largest nonimmune hydrops fetalis panel (62%). The largest nonimmune hydrops fetalis targeted gene panel would have had a diagnostic yield of 18% compared with 29% with exome sequencing. The exome sequencing platform used provided 30× or more coverage for all of the exons on the commercial targeted gene panels, supporting our assumption of 100% analytical sensitivity for exome sequencing.

CONCLUSION

The broader coverage of exome sequencing for genetically heterogeneous disorders, such as nonimmune hydrops fetalis, made it a superior alternative to targeted gene panel testing.

Preimplantation Genetic Diagnosis in Hereditary Hearing Impairment

Sensorineural hearing impairment is a common sensory deficit in children and more than 50% of these cases are caused by genetic etiologies, that is, hereditary hearing impairment (HHI). Recent advances in genomic medicine have revolutionized the diagnostics of, and counseling for, HHI, including preimplantation genetic diagnosis (PGD), thus providing parents-to-be with better reproductive choices. Over the past decade, we have performed PGD using the amplification refractory mutation system quantitative polymerase chain reaction (ARMS-qPCR) technique in 11 couples with a history of HHI, namely eight with GJB2 variants, one with OTOF variants, one with SLC26A4 variants, and one with an MITF variant. We demonstrated that PGD can be successfully applied to HHI of different inheritance modes, namely autosomal dominant or recessive, and phenotypes, namely syndromic or non-syndromic HHI. However, certain ethical concerns warrant scrutiny before PGD can be widely applied to at-risk couples with a history of HHI.

Identification of a novel KAT6A variant in an infant presenting with facial dysmorphism and developmental delay: a case report and literature review

Background

Arboleda-Tham syndrome (ARTHS), caused by a pathogenic variant of KAT6A, is an autosomal dominant inherited genetic disorder characterized by various degrees of developmental delay, dysmorphic facial appearance, cardiac anomalies, and gastrointestinal problems.

Case presentation

A baby presented multiple facial deformities including a high arched and cleft palate, with philtral ridge and vermilion indentation, a prominent nasal bridge, a thin upper lip, low-set ears, an epicanthal fold, and cardiac malformations. Whole exome sequencing (WES) revealed a heterozygous nonsense mutation in exon 8 of the KAT6A gene (c.1312C>T, p.[Arg438*]) at 2 months of age. After a diagnosis of ARTHS, an expressive language delay was observed during serial assessments of developmental milestones.

Conclusions

In this study, we describe a case with a novel KAT6A variant first identified in Korea. This case broadens the scope of clinical features of ARTHS and emphasizes that WES is necessary for early diagnosis in patients with dysmorphic facial appearances, developmental delay, and other congenital abnormalities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01148-x.

Comorbidities associated with genetic abnormalities in children with intellectual disability

Intellectual disability (ID) has emerged as the commonest manifestation of underlying genomic abnormalities. Given that molecular genetic tests for diagnosis of ID usually require high costs and yield relatively low diagnostic rates, identification of additional phenotypes or comorbidities may increase the genetic diagnostic yield and are valuable clues for pediatricians in general practice. Here, we enrolled consecutively 61 children with unexplained moderate or severe ID and performed chromosomal microarray (CMA) and sequential whole-exome sequencing (WES) analysis on them. We identified 13 copy number variants in 12 probands and 24 variants in 25 probands, and the total diagnostic rate was 60.7%. The genetic abnormalities were commonly found in ID patients with movement disorder (100%) or with autistic spectrum disorder (ASD) (93.3%). Univariate analysis showed that ASD was the significant risk factor of genetic abnormality (P = 0.003; OR 14, 95% CI 1.7–115.4). At least 14 ID-ASD associated genes were identified, and the majority of ID-ASD associated genes (85.7%) were found to be expressed in the cerebellum based on database analysis. In conclusion, genetic testing on ID children, particularly in those with ASD is highly recommended. ID and ASD may share common cerebellar pathophysiology.

Diagnosing neuronopathic Gaucher disease: New considerations and challenges in assigning Gaucher phenotypes

Gaucher disease (GD), resulting from biallelic mutations in the gene GBA1, is a monogenic recessively inherited Mendelian disorder with a wide range of phenotypic presentations. The more severe forms of the disease, acute neuronopathic GD (GD2) and chronic neuronopathic GD (GD3), also have a continuum of disease severity with an overlap in manifestations and limited genotype-phenotype correlation. In very young patients, assigning a definitive diagnosis can sometimes be challenging. Several recent studies highlight specific features of neuronopathic GD that may provide diagnostic clues. Distinguishing between the different GD types has important therapeutic implications. Currently there are limited treatment options specifically for neuronopathic GD due to the difficulty in delivering therapies across the blood-brain barrier. In this work, we present both classic and newly appreciated aspects of the Gaucher phenotype that can aid in discriminating between acute and chronic neuronopathic GD, and highlight the continuing therapeutic challenges.

Detection of Disease-Causing SNVs/Indels and CNVs in Single Test Based on Whole Exome Sequencing: A Retrospective Case Study in Epileptic Encephalopathies

Background: Epileptic encephalopathies (EEs) are a pediatric entity with highly phenotypic and genetic heterogeneity. Both single nucleotide variants (SNVs)/Indels and copy number variations (CNVs) could be the causes. Whole exome sequencing (WES) is widely applied to detect SNVs/Indels, but the bioinformatics approach for detecting CNVs is still limited and weak. In the current study, the possibility of profiling both disease-causing SNVs/Indels and CNVs in a single test based on WES in EEs was evaluated. Methods: The infants diagnosed with EEs were enrolled from a single pediatric epilepsy center between January 2018 and February 2020. Demographic and clinical data were collected. In WES data, the pathogenic SNVs were identified through an in-house pipeline, and pathogenic CNVs were identified by CNVkit. The diagnostic rate was evaluated, and the molecular findings were characterized. Results: A total of 73 infants were included; 36 (49.32%) of them were males. The median age was 7 months. Thirty-two (43.84%) infants had been diagnosed with epilepsy syndrome. The most common type of syndrome was West syndrome (22/73, 30.1%), followed by Dravet syndrome (20/77, 27.4%). Fifty-four (73.97%) had intellectual development delay. The genetic cause of EEs, pathogenic or likely pathogenic variants, were successfully discovered in 46.6% (34/73) of the infants, and 29 (39.7%) infants carried SNVs/Indels, while 5 (6.8%) carried CNVs. The majority of the disease-causing variants were inherited in de novo pattern (25, 71.4%). In addition to showing that the variants in the ion channel encoding genes accounted for the main etiology, we discovered and confirmed two new disease-causing genes, CACNA1E and WDR26. Five discovered CNVs were deletions of 2q24.3, 1p36, 15q11-q13, 16p11.2, and 17p13.3, and all were confirmed by array comparative genomic hybridization. Conclusion: The application of both SNVs/Indels and CNVs detection in a single test based on WES yielded a high diagnosis rate in EEs. WES may serve as a first-tier test with cost-effective benefit in EEs.

Genetic analysis of intellectual disability and autism

Background and aim:

Intellectual disability (ID) and autism spectrum disorders (ASD) are neurodevelopmental conditions that often co-exist and affect children from birth, impacting on their cognition and adaptive behaviour. Social interaction and communication ability are also severely impaired in ASD. Almost 1-3% of the population is affected and it has been estimated that approximately 30% of intellectual disability and autism is caused by genetic factors. The aim of this review is to summarize monogenic conditions characterized by intellectual disability and/or autism for which the causative genes have been identified.

Methods and Results:

We identified monogenic ID/ASD conditions through PubMed and other NCBI databases. Many such genes are located on the X chromosome (>150 out of 900 X-linked protein-coding genes), but at least 2000 human genes are estimated to be involved in ID/ASD. We selected 174 genes (64 X-linked and 110 autosomal) for an NGS panel in order to screen patients with ID and/or ASD, after fragile X syndrome and significant Copy Number Variants have been excluded.

Conclusions:

Accurate clinical and genetic diagnosis is required for precise treatment of these disorders, but due to their genetic heterogeneity, most cases remain undiagnosed. Next generation sequencing technologies have greatly enhanced the identification of new genes associated with intellectual disability and autism, ultimately leading to the development of better treatment options. (www.actabiomedica.it)

Single nucleotide polymorphism array analysis of 102 patients with developmental delay and/or intellectual disability from Fujian, China

Developmental delay/intellectual disability (DD/ID) is a complex and phenotypically heterogeneous neurodevelopmental disorder characterized by significant deficits in cognitive and adaptive skills, debuting during the developmental period. In this study, we evaluated the usefulness of single nucleotide polymorphism (SNP) array in the detection of genetic causes of 102 DD/ID patients from Fujian (China). Of them, clinically relevant variants (including pathogenic and likely pathogenic), variants of uncertain significance (VOUS), and no clinically relevant variants (including likely benign and benign) were detected in 19, 4 and 79 patients, accounting for 18.6%, 3.9% and 77.5%, respectively, with a diagnostic yield of 18.6% in our study. Furthermore, we divided 19 clinically relevant variants into 4 groups, including chromosome aneuploidy (n = 1); large copy number variants (CNVs) (>10 Mb) (n = 8); known genomic disorders (n = 8), and likely pathogenic CNVs (n = 2). Moreover, we discussed our findings with respect to 4 cases of VOUS. Overall, we confirmed that DD/ID is a genetically heterogeneous condition and emphasized the importance of using genome-wide SNP array in the detection of its genetic causes. Additionally, we provided clinical and molecular data of patients with causal chromosomal aberrations, and discussed the potential implication in DD/ID of genes located within those CNVs or regions of homozygosity.

Parallel Tests of Whole Exome Sequencing and Copy Number Variant Sequencing Increase the Diagnosis Yields of Rare Pediatric Disorders

Background: Both whole exome sequencing and copy number variants sequencing were applied to identify the genetic cause of rare pediatric disorders. In our study, we aimed to investigate the diagnostic yield of parallel tests of trio whole exome sequencing and copy number variants sequencing and its clinical utility. Methods: After collecting detailed clinical information, a total of 60 patients were referred to parallel tests of whole exome sequencing and copy number variants sequencing, which used shared initial libraries. Results: 26 pathogenic or likely pathogenic single nucleotide variants and 11 copy number variants were identified in 32 patients. 65.4% (17/26) of the SNVs were novel. The overall diagnosis rate was 53.3%. For the patients with positive results, 22 (36.7%) patients were diagnosed by whole exome sequencing and 10 (16.7%) patients were diagnosed by copy number variants sequencing. We also reviewed clinical impact on selected cases. Conclusion: We adopted an approach by performing parallel tests of trio whole exome sequencing and copy number variants sequencing with shared initial libraries. This strategy is relatively efficient and cost-effective for the diagnosis of rare pediatric disorders with high heterogeneity.