Biallelic variants in RBM42 cause a multisystem disorder with neurological, facial, cardiac, and musculoskeletal involvement

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.

¿Qué puede esconder el retraso global del desarrollo? A propósito de un caso de causa genética / What can Global Developmental Delay Conceal? Apropos of a Case with a Genetic Cause

Se presenta un niño de 6 años con antecedente de retraso del lenguaje que llevó a sus padres a realizar múltiples consultas. En un primer momento, su cuadro fue interpretado como parte de un retraso global del desarrollo. Posteriormente, el paciente presentó convulsiones y episodios de descompensación metabólica, comenzando desde entonces su seguimiento por los Servicios de neurología, genética y metabolismo. Finalmente, tras varios estudios complementarios, por medio de un exoma trío se arribó al diagnóstico de síndrome de microduplicación del cromosoma 7q11.23, lo que justifica tanto el retraso global de desarrollo del paciente como su clínica neurológica. (AU)

A six-year-old boy presents with a history of language delay that led his parents to make multiple consultations. At first, we interpreted his condition as part of a global developmental delay. Subsequently, the patient presented seizures and episodes of metabolic decompensation, and since then, he had to be followed up by neurology, genetics, and metabolism services. Finally, after several complementary studies, following a trio exome analysis, we diagnosed chromosome 7q11.23 microduplication syndrome, which explains his global developmental delay and neurological symptoms. (AU)

A case of intellectual developmental disorder with behavioral abnormalities and craniofacial dysmorphism with or without seizures caused by PHF21A gene variation and review of literature / 中华儿科杂志

Objective: To discuss the clinical and genetic features of intellectual developmental disorder with behavioral abnormalities and craniofacial dysmorphism with or without seizures (IDDBCS). Methods: The clinical and genetic records of a patient who was diagnosed with IDDBCS caused by PHF21A gene variation at Children's Hospital Capital Institute of Pediatrics in 2021 were collected retrospectively. Using " PHF21A gene" as the keyword, relevant articles were searched at CNKI, Wanfang Data and PubMed from establishment of databases to February 2023. Clinical and genetic features of IDDBCS were summarized in the combination of this case. Results: An 8 months of age boy showed overgrowth (height, weight and head circumference were all higher than the 97th percentile of children of the same age and sex) and language and motor developmental delay after birth, and gradually showed autism-like symptoms like stereotyped behavior and poor eye contact. At 8 months of age, he began to show epileptic seizures, which were in the form of a series of spastic seizures with no reaction to adrenocorticotropic hormone but a good response to vigabatrin. Physical examination showed special craniofacial appearances including a prominent high forehead, sparse eyebrows, broad nasal bridge, and downturned mouth with a tent-shaped upper lip. The patient also manifested hypotonia. Whole exome sequencing showed a de novo heterogeneous variant, PHF21A (NM_001101802.1): c.54+1G>A, and IDDBCS was diagnosed. A total of 6 articles (all English articles) were collected, involving this case and other 14 patients of IDDBCS caused by PHF21A gene variation. Clinical manifestations were intellectual disability or developmental delay (15 patients), craniofacial anomalies (15 patients), behavioral abnormalities (12 patients), seizures (9 patients), and overgrowth (8 patients). The main pathogenic variations were frameshift variations (8 patients). Conclusions: IDDBCS should be considered when patients show nervous developmental abnormalities, craniofacial anomalies, seizures and overgrowth. PHF21A gene variation detection helps to make a definite diagnosis.

Analysis of genetic variants in a child with Intellectual developmental disorder with behavioral abnormalities and craniofacial dysmorphism without seizures / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical phenotype and genetic characteristics of a child with Intellectual developmental disorder with behavioral abnormalities and craniofacial malformations without epilepsy (IDDBCS).@*METHODS@#A child who had visited the Lianyungang Maternal and Child Health Care Hospital in April 2021 was selected as the study subject. Clinical data of the child were collected. Genomic DNA was extracted from peripheral blood samples of the child and his parents and subjected to whole exome sequencing (WES). Candidate variants were verified by Sanger sequencing of his family members.@*RESULTS@#The child, a 3-year-and-4-month-old male, had presented with global developmental delay and cranial malformation. Genetic testing revealed that he has harbored a heterozygous c.1703delA (p.K568Sfs9) variant of the PHF21A gene, for which both of his parents were of the wild type. This low-frequency variant may alter the structure and function of the protein product. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), it was classified as a pathogenic variant (PVS1+PS2+PM2_Supporting).@*CONCLUSION@#The heterozygous c.1703delA (p.K568Sfs9) variant of the PHF21A gene probably underlay the IDDBCS in this patient.

Analysis of a child with Verheij syndrome due to variant of PUF60 gene / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical phenotype and genetic variant in a child with Verheij syndrome (VRJS).@*METHODS@#A child who had presented at the Soochow University Affiliated Children's Hospital and Wujiang District Children's Hospital in July 2022 for "elevated scapula since early childhood" was selected as the study subject. Peripheral blood samples of the child and his parents were collected and subjected to whole exome sequencing. Candidate variant was verified by Sanger sequencing and bioinformatic analysis.@*RESULTS@#The child had manifested elevated scapulae, torticollis, neck asymmetry, facial dysmorphism, dispersed café-au-lait spots, limited mobility of upper limbs and shoulder joints, and intellectual disability. Sequencing revealed that he has harbored a de novo heterozygous c.405dupT (p.Ile136Tyrfs*4) variant of the PUF60 gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), this variant was classified as pathogenic (PVS1+PS2_moderate+PM2_supporting). Combined his clinical features and result of genetic testing, the child was diagnosed with VRJS due to variant of the PUF60 gene.@*CONCLUSION@#The clinical manifestations of VRJS include facial dysmorphism, intellectual disability, elevated scapulae, vertebral fusion, other skeletal malformations, without significant abnormalities of the heart, kidney, and eyes, which need to be distinguished from Klippel-Feil syndrome. Above finding has expended the mutation spectrum of the PUF60 gene and provided a reference for delineation of the genotype-phenotype correlation of the VRJS.

Analysis of clinical features and ATRX gene variants in a Chinese pedigree affected with X-linked alpha thalassemia mental retardation (ATR-X) syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical characteristics and genetic basis of two brothers featuring X-linked alpha thalassemia mental retardation (ATR-X) syndrome.@*METHODS@#An infant who had presented at the Qilu Children's Hospital in 2020 for unstable upright head and inability to roll over and his family were selected as the study subjects. The clinical features of the child and one of his brothers were summarized, and their genomic DNA was subjected to targeted capture and next generation sequencing (NGS).@*RESULTS@#The brothers had presented with mental retardation and facial dysmorphisms. NGS revealed that they had both harbored a hemizygous c.5275C>A variant of the ATRX gene located on the X chromosome, which was inherited from their mother.@*CONCLUSION@#The siblings were diagnosed with ATR-X syndrome. The discovery of the c.5275C>A variant has enriched the mutational spectrum of the ATRX gene.

Genetic analysis of a Chinese pedigree affected with overgrowth syndrome due to a small supernumerary marker chromosome / 中华医学遗传学杂志

OBJECTIVE@#To carry out genetic analysis for a Chinese pedigree affected with intellectual disability and overgrowth due to a supernumerary marker chromosome (sSMC).@*METHODS@#A pedigree which had presented at Jiaxing Maternity and Child Health Care Hospital on August 31, 2021 was selected as the study subject, for which chromosomal karyotyping, single nucleotide polymorphism-based microarray (SNP-array), and fluorescence in situ hybridization (FISH) were carried out in combination.@*RESULTS@#SNP-array analysis showed that the proband and his sister had both harbored a 16.1 Mb duplication which encompassed the critical region of 15q26 overgrowth syndrome. FISH confirmed that the proband was 47,XX,+neo(15)(qter→q25.3:)mat, her mother was 47,XX,del(15)(q25.3:),+neo(15)(qter→q25.3:), whilst her father was normal.@*CONCLUSION@#Application of multiple genetic techniques has facilitated delineation of the origin of sSMC and reliable genetic counseling for this pedigree.

Helsmoortel-Van der Aa syndrome due to hotspot mutation of ADNP gene and a literature review / 中华医学遗传学杂志

OBJECTIVE@#To summarize the clinical features and biological characteristics of Helsmoortel Van der Aa syndrome (HVDAS) due to hotspot mutations of the ADNP gene in order to facilitate early diagnosis.@*METHODS@#Clinical data and result of genetic testing for a girl with HVDAS due to hotspot mutation of the ADNP gene was summarized. Related literature was also reviewed.@*RESULTS@#The patient, a 2-year-old girl, had presented with growth retardation, facial dysmorphism, psychomotor and language delay and recurrent respiratory infections. Whole exome sequencing revealed that she has harbored a heterozygous c.2496_2499delTAAA (p.Asn832Lysfs*81) variant of the ADNP gene, which was not found in either of her parents.@*CONCLUSION@#Although the typical features of the HVDAS have included intellectual disability and autism spectrum disorders, growth retardation and premature primary tooth eruption may also be present. In addition, the phenotypic difference among individuals carrying hot spot variants of the ADNP gene was not prominent.

Analysis of ARID1B gene variant in a patient with mental retardation and ejaculatory dysfunction / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical characteristics and genetic etiology of a patient with mental retardation and ejaculatory dysfunction.@*METHODS@#A patient with mental retardation and ejaculatory dysfunction who was admitted to the First Affiliated Hospital of Air Force Military Medical University on November 18, 2021 was selected as the study subject. Clinical data of the patient were collected. Peripheral venous blood samples were collected from the patient and his parents. Whole exome sequencing (WES) was carried out for the patient, and the candidate variant was verified by Sanger sequencing and bioinformatic analysis.@*RESULTS@#The patient, a 26-year-old male, had manifested atypical mental retardation and ejaculatory dysfunction. WES revealed that he has harbored a heterozygous variant of the ARID1B gene, namely c.5776C>T (p.Arg1926X). Sanger sequencing verified that neither of his parents has carried the same variant. The variant has been recorded in the 1000 Genomes, ExAC, gnomAD and ClinVar databases. A search of the dbSNP database suggested that the variant has a population frequency of 0.000 4%. The variant was predicted as deleterious by online software including Mutation Taster, CADD, and MutPred. Analysis with Cluster Omega online software suggested that the amino acid encoded by the variant site was highly conserved among various species. Analysis with PyMOL software suggested that the variant may affect the function of the encoded protein. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG) and ClinGen, the variant was predicted to be pathogenic.@*CONCLUSION@#The c.5776C>T (p.Arg1926X) variant of the ARID1B gene probably underlay the mental retardation and ejaculatory dysfunction in this patient. Above finding has broadened the spectrum of the ARID1B gene variants and provided reference for the diagnosis and treatment of the patient.

Analysis of CNNM2 gene variant in a child with Hypomagnesemia, seizures, and mental retardation syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic etiology of a child with Hypomagnesemia, epilepsy and mental retardation syndrome (HSMR).@*METHODS@#A child who was admitted to the Children's Hospital of Shandong University on July 9, 2021 due to repeated convulsions for 2 months was selected as the study subject. Clinical data of the child was collected. Peripheral blood samples of the child and his pedigree members were collected for the extraction of genomic DNA. Whole exome sequencing was carried out, and candidate variant was verified by Sanger sequencing and bioinformatic analysis.@*RESULTS@#The child, a 1-year-and-7-month-old male, had presented with epilepsy and global developmental delay. Serological testing revealed that he has low serum magnesium. Genetic testing showed that the child has harbored a heterozygous c.1448delT (p.Val483GlyfsTer29) variant of the CNNM2 gene, which was de novo in origin. The variant has caused substitution of the Valine at position 483 by Glycine and formation of a termination codon after 29 amino acids at downstream. As predicted by Swiss-Model online software, the variant may alter the protein structure, resulting in a truncation. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the c.1448delT (p.Val483GlyfsTer29) was predicted as a pathogenic variant (PVS1+PS2+PM2_Supporting+PP4).@*CONCLUSION@#The heterozygous c.1448delT variant of the CNNM2 gene probably underlay the HSMR in this child. Above finding has enriched the phenotype-genotype spectrum of the CNNM2 gene.

Genetic analysis of a Chinese pedigree with Cohen syndrome due to compound heterozygous variants of VPS13B gene / 中华医学遗传学杂志

OBJECTIVE@#To investigate the clinical phenotype and genetic characteristics of a Chinese pedigree affected with Cohen syndrome.@*METHODS@#A proband who was admitted to Zhengzhou People's Hospital on June 2, 2021 due to intellectual disability and developmental delay, in addition with her younger sister and other family members, were selected as the study subjects. Clinical data of the proband and her younger sister were collected. Genomic DNA was extracted from peripheral venous blood and chorionic villi samples. Chromosomal abnormalities were detected with chromosomal microarray analysis (CMA). Whole exome sequencing (WES) and Sanger sequencing were carried out to detect candidate variants in the proband. With RNA extracted from the peripheral blood samples, VPS13B gene transcripts and expression were analyzed by PCR and real-time quantitative PCR. Prenatal diagnosis was carried out at 12 weeks' gestation.@*RESULTS@#The proband was a 10-year-old female with clinical manifestations including development delay, obesity, severe myopia and peculiar facial features. Her sister was 3 years old with a similar phenotype. CMA revealed no chromosomal abnormality in the proband, while WES results revealed that the proband and her sister had both harbored compound heterozygous variants of the VPS13B gene, namely c.10076_10077delCA (p.T3359fs*29) and c.6940+1G>T, which were respectively inherited from their mother and father. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), both variants were classified as pathogenic (PVS1+PS4+PM4+PP1; PVS1+PM2_Supporting+PM3+PP1). In vivo splicing assay confirmed that the c.6940+1G>T variant has produced a frameshift transcript with skipping of exon 38. Compared with the control group, the expression of RNA in the peripheral blood of the proband's parents has decreased to 65% ~ 70% (P < 0.01), whilst that in the proband and her sister has decreased to 40% (P < 0.001). Prenatal diagnosis at 12 weeks of gestation has found that the fetus only harbored the heterozygous c.10076_ 10077delCA variant.@*CONCLUSION@#The c.10076_10077delCA (p.T3359fs*29) frameshift variant and c.6940+1G>T splicing variant probably underlay the Cohen syndrome in this pedigree. Genetic testing has facilitated the diagnosis of this disease.

Clinical and genetic characteristics of 9 rare cases with coexistence of dual genetic diagnoses / 中华儿科杂志

Objective: To analyze the clinical and genetic characteristics of pediatric patients with dual genetic diagnoses (DGD). Methods: Clinical and genetic data of pediatric patients with DGD from January 2021 to February 2022 in Peking University First Hospital were collected and analyzed retrospectively. Results: Among the 9 children, 6 were boys and 3 were girls. The age of last visit or follow-up was 5.0 (2.7,6.8) years. The main clinical manifestations included motor retardation, mental retardation, multiple malformations, and skeletal deformity. Cases 1-4 were all all boys, showed myopathic gait, poor running and jumping, and significantly increased level of serum creatine kinase. Disease-causing variations in Duchenne muscular dystrophy (DMD) gene were confirmed by genetic testing. The 4 children were diagnosed with DMD or Becker muscular dystrophy combined with a second genetic disease, including hypertrophic osteoarthropathy, spinal muscular atrophy, fragile X syndrome, and cerebral cavernous malformations type 3, respectively. Cases 5-9 were clinically and genetically diagnosed as COL9A1 gene-related multiple epiphyseal dysplasia type 6 combined with NF1 gene-related neurofibromatosis type 1, COL6A3 gene-related Bethlem myopathy with WNT1 gene-related osteogenesis imperfecta type XV, Turner syndrome (45, X0/46, XX chimera) with TH gene-related Segawa syndrome, Chromosome 22q11.2 microduplication syndrome with DYNC1H1 gene-related autosomal dominant lower extremity-predominant spinal muscular atrophy-1, and ANKRD11 gene-related KBG syndrome combined with IRF2BPL gene-related neurodevelopmental disorder with regression, abnormal movement, language loss and epilepsy. DMD was the most common, and there were 6 autosomal dominant diseases caused by de novo heterozygous pathogenic variations. Conclusions: Pediatric patients with coexistence of double genetic diagnoses show complex phenotypes. When the clinical manifestations and progression are not fully consistent with the diagnosed rare genetic disease, a second rare genetic disease should be considered, and autosomal dominant diseases caused by de novo heterozygous pathogenic variation should be paid attention to. Trio-based whole-exome sequencing combining a variety of molecular genetic tests would be helpful for precise diagnosis.

Börjeson -Forssman -Lehmann syndrome: A case report / 中南大学学报(医学版)

Börjeson-Forssman-Lehmann syndrome (BFLS) is a rare X-linked intellectual disability. The main features of the patients include intellectual disability/global developmental delay, characteristic face, anomalies of fingers and toes, hypogonadism, linear skin hyperpigmentation, and tooth abnormalities in female patients, and obesity in male patients. A case of BFLS caused by a novel mutation of PHF6 gene who was treated in the Department of Pediatrics, Xiangya Hospital, Central South University was reported. The 11 months old girl presented the following symptons: Global developmental delay, characteristic face, sparse hair, ocular hypertelorism, flat nasal bridge, hairy anterior to the tragus, thin upper lip, dental anomalies, ankyloglossia, simian line, tapering fingers, camptodactylia, and linear skin hyperpigmentation. The gene results of the second-generation sequencing technology showed that there was a novel heterozygous mutation site c.346C>T (p.Arg116*) of the PHF6 (NM032458.3), variation rating as pathogenic variation. During the follow-up, the patient developed astigmatism, strabismus, awake bruxism, and stereotyped behavior, and the linear skin hyperpigmentation became gradually more evident. The disease is lack of effective therapy so far.

Genetic analysis of two children with developmental delay and intellectual disability / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic etiology of two patients with developmental delay and intellectual disability.@*METHODS@#Two children who were respectively admitted to Henan Provincial People's Hospital on August 29, 2021 and August 5, 2019 were selected as the study subjects. Clinical data were collected, and array comparative genomic hybridization (aCGH) was carried out on the children and their parents for the detection of chromosomal microduplication/microdeletions.@*RESULTS@#Patient 1 was a 2-year-and-10-month female and patient 2 was a 3-year-old female. Both children had featured developmental delay, intellectual disability, and abnormal findings on cranial MRI. aCGH revealed that patient 1 has harbored arr[hg19] 6q14.2q15(84621837_90815662)×1, a 6.19 Mb deletion at 6q14.2q15, which encompassed ZNF292, the pathogenic gene for Autosomal dominant intellectual developmental disorder 64. Patient 2 has harbored arr[hg19] 22q13.31q13.33(46294326_51178264)×1, a 4.88 Mb deletion at 22q13.31q13.33 encompassing the SHANK3 gene, haploinsufficiency of which can lead to Phelan-McDermid syndrome. Both deletions were classified as pathogenic CNVs based on the guidelines of American College of Medical Genetics and Genomics (ACMG) and were not found in their parents.@*CONCLUSION@#The 6q14.2q15 deletion and 22q13-31q13.33 deletion probably underlay the developmental delay and intellectual disability in the two children, respectively. Haploinsufficiency of the ZNF292 gene may account for the key clinical features of the 6q14.2q15 deletion.

Analysis of a child with X-linked intellectual disability due to a maternal de novo splicing variant of the PAK3 gene / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic etiology for a child with profound intellectual disabilities and obvious behavioral abnormalities.@*METHODS@#A male child who had presented at the Zhongnan Hospital of Wuhan University on December 2, 2020 was selected as the study subject. Peripheral blood samples of the child and his parents were collected and subjected to whole exome sequencing (WES). Candidate variant was verified by Sanger sequencing. Short tandem repeat (STR) analysis was carried out to determine its parental origin. The splicing variant was also validated in vitro with a minigene assay.@*RESULTS@#WES results revealed that the child had harbored a novel splicing variant of c.176-2A>G in the PAK3 gene, which was inherited from his mother. The results of minigene assay have confirmed aberrant splicing of exon 2. According to the guidelines from the American College of Medical Genetics and Genomics, it was classified as a pathogenic variant (PVS1+PM2_Supporting+PP3).@*CONCLUSION@#The novel splicing variant c.176-2A>G of the PAK3 gene probably underlay the disorder in this child. Above finding has expanded the variation spectrum of the PAK3 gene and provided a basis for genetic counseling and prenatal diagnosis for this family.

Clinical and genetic analysis of a child with Alazami syndrome due to compound heterozygous variants of LARP7 gene / 中华医学遗传学杂志

OBJECTIVE@#To analyze the clinical phenotype and genetic basis of a child with Alazami syndrome (AS).@*METHODS@#A child who presented at Tianjin Children's Hospital on June 13, 2021 was selected as the study subject. The child was subjected to whole exome sequencing (WES), and candidate variants were verified by Sanger sequencing.@*RESULTS@#WES revealed that the child has harbored two frameshifting variants of the LARP7 gene, namely c.429_430delAG (p.Arg143Serfs*17) and c.1056_1057delCT (p.Leu353Glufs*7), which were verified by Sanger sequencing to be respectively inherited from his father and mother.@*CONCLUSION@#The compound heterozygous variants of the LARP7 gene probably underlay the pathogenesis in this child.

Clinical features and genetic analysis of a child with EAST/SeSAME syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for a EAST/SeSAME syndrome child featuring epilepsy, ataxia, sensorineural deafness and intellectual disability.@*METHODS@#A child with EAST/SeSAME syndrome who had presented at the Third Affiliated Hospital of Zhengzhou University in January 2021 was selected as the study object. Peripheral blood samples of the child and her parents were collected and subjected to whole exome sequencing. Candidate variants were verified by Sanger sequencing.@*RESULTS@#Genetic testing revealed that the child has harbored compound heterozygous variants of the KCNJ10 gene, namely c.557T>C (p.Val186Ala) and c.386T>A (p.Ile129Asn), which were inherited from her mother and father, respectively. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), both variants were predicted as likely pathogenic (PM1+PM2_Supporting+PP3+PP4; PM1+PM2_Supporting+PM3+PP3+PP4).@*CONCLUSION@#The patient was diagnosed with EAST/SeSAME syndrome due to the compound heterozygous variants of the KCNJ10 gene.

Analysis of genetic variants and clinical manifestations of two children with Kabuki syndrome / 中华医学遗传学杂志

OBJECTIVE@#To report on two children with Kabuki syndrome due to variants of the KMT2D gene and summarize their clinical and genetic characteristics.@*METHODS@#Two children who had presented at the Ningbo Women and Children's Hospital respectively on August 19 and November 10, 2021 were selected as the study subjects. Clinical data were collected. Both children were subjected to whole exome sequencing (WES), and candidate variants were validated by Sanger sequencing.@*RESULTS@#Both children had featured motor and language developmental delay, facial dysmorphism and mental retardation. Genetic testing revealed that both had harbored de novo heterozygous variants of the KMT2D gene, namely c.10205del (p.Leu3402Argfs*3) and c.5104C>T (p.Arg1702*), both of which were rated as pathogenic variants based on the guidelines from the American College of Medical Genetics and Genomics (ACMG).@*CONCLUSION@#The c.10205del (p.Leu3402Argfs*3) and c.5104C>T (p.Arg1702*) variants of the KMT2D gene probably underlay the pathogenesis in these two children. Above finding has not only provided a basis for their diagnosis and genetic counseling, but also enriched the spectrum of KMT2D gene variants.

Clinical and genetic analysis of a child with Mental retardation autosomal dominant 51 / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical characteristics and genetic basis of a child with Mental retardation autosomal dominant 51 (MRD51).@*METHODS@#A child with MRD51 who was hospitalized at Guangzhou Women and Children's Medical Center on March 4, 2022 was selected as the study subject. Clinical data of the child was collected. Peripheral blood samples of the child and her parents were collected and subjected to whole exome sequencing (WES). Candidate variants were verified by Sanger sequencing and bioinformatic analysis.@*RESULTS@#The child, a 5-year-and-3-month-old girl, had manifested autism spectrum disorder (ASD), mental retardation (MR), recurrent febrile convulsions and facial dysmorphism. WES revealed that she has harbored a novel heterozygous variant of c.142G>T (p.Glu48Ter) in the KMT5B gene. Sanger sequencing confirmed that neither of her parents has carried the same variant. The variant has not been recorded in the ClinVar, OMIM and HGMD, ESP, ExAC and 1000 Genomes databases. Analysis with online software including Mutation Taster, GERP++ and CADD indicated it to be pathogenic. Prediction with SWISS-MODEL online software suggested that the variant may have a significant impact on the structure of KMT5B protein. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was predicted to be pathogenic.@*CONCLUSION@#The c.142G>T (p.Glu48Ter) variant of the KMT5B gene probably underlay the MRD51 in this child. Above finding has expanded the spectrum of KMT5B gene mutations and provided a reference for clinical diagnosis and genetic counseling for this family.

Genetic analysis of a child with Pitt-Hopkins syndrome due to a novel variant of TCF4 gene derived from low percentage maternal mosaicism / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic etiology of a child with Pitt-Hopkins syndrome.@*METHODS@#A child who had presented at the Medical Genetics Center of Gansu Provincial Maternal and Child Health Care Hospital on February 24, 2021 and his parents were selected as the study subjects. Clinical data of the child was collected. Genomic DNA was extracted from peripheral blood samples of the child and his parents and subjected to trio-whole exome sequencing (trio-WES). Candidate variant was verified by Sanger sequencing. Karyotype analysis was also carried out for the child, and her mother was subjected to ultra-deep sequencing and prenatal diagnosis upon her subsequent pregnancy.@*RESULTS@#The clinical manifestations of the proband included facial dysmorphism, Simian crease, and mental retardation. Genetic testing revealed that he has carried a heterozygous c.1762C>T (p.Arg588Cys) variant of the TCF4 gene, for which both parents had a wild-type. The variant was unreported previously and was rated as likely pathogenic based on the guidelines of the American College of Medical Genetics and Genomics (ACMG). Ultra-deep sequencing indicated that the variant has a proportion of 2.63% in the mother, suggesting the presence of low percentage mosaicism. Prenatal diagnosis of amniotic fluid sample suggested that the fetus did not carry the same variant.@*CONCLUSION@#The heterozygous c.1762C>T variant of the TCF4 gene probably underlay the disease in this child and has derived from the low percentage mosaicism in his mother.