Molecular autopsy in Chinese sudden cardiac death in the young.

Inherited cardiovascular conditions are significant causes of sudden cardiac death in the young (SCDY), making their investigation using molecular autopsy and prevention a public health priority. However, the molecular autopsy data in Chinese population is lacking. The 5-year result (2017-2021) of molecular autopsy services provided for victims of SCDY (age 1-40 years) was reviewed. The outcome of family cascade genetic screening and clinical evaluation was reviewed. A literature review of case series reporting results of molecular autopsy on SCDY in 2016-2023 was conducted. Among the 41 decedents, 11 were found to carry 13 sudden cardiac death (SCD)-causative genetic variants. Likely pathogenic (LP) variants were identified in the DSP, TPM1, TTN, and SCN5A genes. Cascade genetic testing identified four family members with LP variants. One family member with familial TPM1 variant was found to have hypertrophic cardiomyopathy upon clinical evaluation. This study provided insight into the genetic profile of molecular autopsy in a Chinese cohort of SCDY. The detection of important SCD-causative variants through molecular autopsy has facilitated family cascade screening by targeted genetic testing and clinical evaluation of at-risk family members. A literature review of the current landscape of molecular autopsy in the investigation of SCDY was conducted.

Clinical and molecular characteristics of hemophilia A affected individuals and carriers: A 24 years experience from three centers.

Hemophilia A is a rare bleeding disorder with variable expressivity and allelic heterogeneity. Despite the advancement of prenatal diagnostics and molecular studies, the number of studies reviewing the reproductive choices of hemophilia A carriers and affected individuals remains limited. Through this retrospective review, we hope to gain a deeper understanding of hemophilia A-affected individuals' clinical and molecular characteristics, as well as the reproductive choices of the at-risk couples. A total of 122 individuals harboring likely causative F8 gene alterations from 64 apparently unrelated families attending three centers between 3/2000 and 3/2023 were included in this study. Their clinical and molecular findings as well as reproductive choices were gathered in a clinical setting and verified through the electronic medical record database of the public health system. Forty-seven affected males and 75 female heterozygous carriers were included in the analysis. Among 64 apparently unrelated families, 36 distinct pathogenic/likely pathogenic variants were identified, of which 30.6% (11/36) of variants were novel. While the majority of clinical findings and genotype-phenotype correlations appear to be in accordance with existing literature, female carriers who had no fertility intention were significantly more likely to have affected sons than those who had fertility intention (5/19 vs. 4/5; p = 0.047). Through this retrospective review, we summarized the clinical and molecular characteristics of 122 individuals harboring pathogenic/likely pathogenic F8 variants, as well as their fertility intentions and reproductive outcomes. Further studies are required to look into the considerations involved in reproductive decision-making.

Successful Treatment of Drug-Resistant Seizures Secondary to Ring 20 Mosaicism with Perampanel as an Add-On Antiepileptic Drug.

We report a girl with drug-resistant seizures, progressive behavioral changes, and cognitive decline. Investigations showed abnormal EEG with frequent high-voltage bifrontotemporal sharp and slow waves, especially during sleep. Seizures were difficult to control, despite the usage of various antiepileptic drugs. Perampanel as an add-on antiepileptic drug appeared efficacious. Due to the recognizable pattern of seizures and EEG findings, a karyotype study was performed which revealed 46 chromosomes with a ring 20 chromosome mosaicism. Ring 20 chromosome is associated with drug-resistant refractory seizures, cognitive decline, and behavioral problems. This case highlights the difficulty and challenge faced in managing drug-resistant refractory seizures associated with ring 20 chromosome. While ring 20 chromosome is often underdiagnosed, one should have a high index of awareness and suspicion of such rare epilepsy syndrome, so that an early diagnosis can be made.

Detecting structural variations with precise breakpoints using low-depth WGS data from a single oxford nanopore MinION flowcell.

Structural variation (SV) is a major cause of genetic disorders. In this paper, we show that low-depth (specifically, 4×) whole-genome sequencing using a single Oxford Nanopore MinION flow cell suffices to support sensitive detection of SV, particularly pathogenic SV for supporting clinical diagnosis. When using 4× ONT WGS data, existing SV calling software often fails to detect pathogenic SV, especially in the form of long deletion, terminal deletion, duplication, and unbalanced translocation. Our new SV calling software SENSV can achieve high sensitivity for all types of SV and a breakpoint precision typically ± 100 bp; both features are important for clinical concerns. The improvement achieved by SENSV stems from several new algorithms. We evaluated SENSV and other software using both real and simulated data. The former was based on 24 patient samples, each diagnosed with a genetic disorder. SENSV found the pathogenic SV in 22 out of 24 cases (all heterozygous, size from hundreds of kbp to a few Mbp), reporting breakpoints within 100 bp of the true answers. On the other hand, no existing software can detect the pathogenic SV in more than 10 out of 24 cases, even when the breakpoint requirement is relaxed to ± 2000 bp.

KBG syndrome in a Chinese population: A case series.

KBG syndrome (OMIM #148050) is an autosomal dominant neurodevelopmental disorder characterized by the presence of macrodontia of the permanent central upper incisors, characteristic facial features, delay in development, intellectual disability, short stature, and various skeletal abnormalities. Over 200 affected individuals have been described worldwide, though underdiagnosis is suspected because the characteristic features are variably present and affected individuals can have a mild phenotype. This case series provides a summary of the clinical and molecular characteristics of 10 Chinese KBG syndrome patients recruited from a single center. To our knowledge, this is the first case series for Chinese KBG patients. This case series aimed at exploring potential ethnicity-related variability in KBG syndrome.

The first case report of Strømme syndrome in a Chinese patient: Expanding the phenotype and literature review.

Strømme syndrome (MIM #243605) is a rare autosomal recessive ciliopathy resulting from compound heterozygous or homozygous pathogenic alterations in the CENPF gene (# 600236). Although there are a number of case reports featuring individuals with clinically compatible Strømme syndrome, only 13 affected individuals had molecular confirmation worldwide. Herein, we report a 24 years old Chinese gentleman with molecularly confirmed Strømme syndrome with compound heterozygous pathogenic nonsense variants in NM_016343.3(CENPF):c.436C > T, p.(Gln146*) and c.9280C > T, p.(Arg3094*). He presented with microcephaly, unilateral microphthalmia, single central upper incisor and bilateral preaxial polydactyly. To our knowledge, this is the first reported Chinese individual with molecularly confirmed Strømme syndrome.

Extending the phenotype of DeSanto-Shinawi syndrome: A case report and literature review.

DeSanto-Shinawi syndrome (DESSH, OMIM #616708) is a rare autosomal dominant neurodevelopmental disorder caused by loss-of-function variants in the WAC gene. Affected individuals are characterized by neonatal hypotonia, developmental delay, intellectual disability, behavioral problems, and dysmorphism. Epilepsy is present in some of the patients with DESSH. By far, less than 30 affected individuals have been reported worldwide. Herein, we report a 9-year-old Chinese girl with molecularly substantiated DESSH with a de novo nonsense c. 1648C>T p.(Arg550*) variant identified in the WAC gene. Aside from developmental delay and the characteristic facial gestalt, our proband also exhibited tethered cord syndrome due to filar lipoma and left duplex kidney complicated with hydronephrosis, features not observed in any of the previously reported individuals with DESSH.

Prenatal phenotype of Kabuki syndrome: A case series and literature review.

OBJECTIVES: Kabuki syndrome (KS) is a genetic disorder characterized by intellectual disability, facial dysmorphism and congenital anomalies. We aim to investigate the prenatal features of fetuses with KS and to provide a comprehensive review of the literature on prenatal sonographic abnormalities associated with KS. METHODS: We retrospectively reviewed the prenatal ultrasound findings of all mothers of children with molecularly confirmed KS in Hong Kong, between 1991 and 2019. We also performed systematic review of the literature to identify studies on the prenatal findings in KS. RESULTS: We identified 11 cases with KS with detectable fetal ultrasound findings ranging from no detectable abnormalities to a variety of non-specific findings including increased nuchal translucency, pleural effusion, cardiac anomalies, renal anomalies, intrauterine growth restriction, polyhydramnios, oligohydramnios and single umbilical artery. In combining our cases with the 77 cases published, 42 (50.6%) of them had more than one abnormal antenatal ultrasound finding. The most frequent ultrasound features observed were cardiac anomalies (49.4%), followed by polyhydramnios (28.9%), genitourinary anomalies (26.5%), single umbilical artery (15.7%), intrauterine growth restriction (14.5%) and hydrops fetalis/pleural effusion/ascites (12.0%). CONCLUSIONS: These cases demonstrate the prenatal phenotypic heterogeneity associated with KS. Although the ultrasound abnormalities are non-specific, KS should be considered in the differential diagnosis when these fetal findings following normal microarray analysis/karyotyping.

Genotype and phenotype in 18 Chinese patients with Coffin-Siris syndrome.

Coffin-Siris syndrome (CSS, MIM# 1359200) is a multisystem congenital disorder characterized by coarse facial features, hypoplasia of the fifth digits and nails, and intellectual disability. It is a genetically heterogeneous condition caused by pathogenic variants in genes encoding proteins of the BAF (BRG1-associated factors) chromatin modeling complex and its downstream transcriptional factor. To date over 220 CSS individuals with pathogenic variants found have been described in the literature. This case series reported 18 molecularly confirmed Chinese individuals (17 with ARIDIB (OMIM*614556) variants and one with SMARCB1 (OMIM*601607) variant) from 17 unrelated families in Hong Kong. The clinical features of these 18 Chinese CSS patients together with two previously reported Chinese patients with ARID1B variants were reviewed. Among the 19 Chinese patients with ARID1B variants, our data suggested a lower prevalence of feeding problem, autistic features, agenesis of corpus callosum (ACC) or partial/hypoplasia of corpus callosum, and sparse hair when compared with previous reports. There was appearing higher prevalence of digital hypoplasia. Digital hypoplasia was observed to become less noticeable with time in some patients. This report highlighted the age-dependent phenotypic presentation of CSS and ethnicity-related effect on ARID1B-CSS phenotype. Moreover, this series included the first family with molecularly confirmed maternal somatic mosaicism of ARID1B variant leading to familial CSS recurrence.

An adult Chinese patient with developmental delay with short stature, dysmorphic features, and sparse hair (Loucks-Innes syndrome).

Variants of the diphthamide biosynthesis I (DPH1, OMIM*603527) are associated with developmental delay, short stature, and sparse hair syndrome (DEDSSH/DPH1 syndrome) (OMIM# 616901). Another name is Loucks-Innes syndrome. DPH1 syndrome is an ultrarare and severe neurodevelopmental disorder. Less than 20 patients were reported from different ethnicities. Here, we described the first Chinese adult with genetically confirmed DPH1 syndrome. We summarized previously reported patients in the literature and found that developmental delay, unusual skull shape, sparse hair, and facial dysmorphism were consistently present in all DPH1 syndrome patients. Dysplastic toenails and dental abnormalities are age-dependent characteristics of DPH1 syndrome. Our patient was the first reported patient with documented growth hormone deficiency. Dental and endocrine checkup should be considered in the routine follow-up of DPH1 syndrome patients.

Clinical and molecular characterization study of Chinese Kabuki syndrome in Hong Kong.

Kabuki syndrome (OMIM #147920 and 300867) is a rare genetic disorder characterized by a distinctive facial gestalt, intellectual disability and multiple congenital anomalies. We summarized the clinical features and molecular findings of the Kabuki syndrome (KS) patients diagnosed in Hong Kong between January 1991 and December 2019. There were 21 molecularly confirmed KS. Twenty of them were due to pathogenic KMT2D variants and one patient had KDM6A deletion. Nine KMT2D variants were novel. The clinical phenotype of our Chinese KS patients was largely comparable with that reported in patients of other ethnicities. This study expands the mutation spectrum but also provide important natural history information of Chinese KS in literature.

Adult Chinese twins with Kenny-Caffey syndrome type 2: A potential age-dependent phenotype and review of literature.

Kenny-Caffey syndrome (KCS) type 2 (OMIM 127000) is a rare syndromic cause of hypoparathyroidism which is characterized by proportionate short stature, long bone abnormalities, delayed closure of anterior fontanelle, eye abnormalities, and normal intelligence. It is caused by variants in FAM111A (NM_001942519.1). In this review, we reported the first Chinese patients, a pair of monozygotic twins, with genetically confirmed KCS type 2 with over 20 years follow-up. We summarized the clinical features of 14 previously reported and genetically confirmed KCS type 2 patients; our twin patients exhibited a unique spinal manifestation which could be an important age-dependent feature of KCS type 2. In this review, over 60% KCS type 2 patients had dental problem and over 80% suffered from refractive errors or structural eye abnormalities. Therefore, early dental, ophthalmological, and orthopedic assessments are warranted for KCS type 2 patients. Micro-orchidism, previously reported in KCS type 2 patients, was also detected in our patients. The possibility of subfertility should be considered in male KCS type 2 patients. A multidisciplinary management approach for this rare syndrome is recommended.

Rubinstein-Taybi syndrome in Chinese population with four novel mutations.

Rubinstein-Taybi syndrome (RSTS, OMIM*180849) is a rare autosomal dominant disorder, characterized by distinctive facial features, short stature, broad and often angulated thumbs and halluces, with occasional congenital anomalies. Characteristic facial dysmorphic features include downslanting palpebral fissures, low hanging columella. RSTS is caused by pathogenic variants in two ubiquitously expressed and highly homologous genes, CREBBP (OMIM*600140) and EP300 (OMIM*600140). Clinical features were well reported especially in Caucasian ethnicity. We would like to report the clinical phenotype of RSTS in our Chinese population and highlight four novel mutations in CREBBP gene.

Rubinstein-Taybi syndrome in diverse populations.

Rubinstein-Taybi syndrome (RSTS) is an autosomal dominant disorder, caused by loss-of-function variants in CREBBP or EP300. Affected individuals present with distinctive craniofacial features, broad thumbs and/or halluces, and intellectual disability. RSTS phenotype has been well characterized in individuals of European descent but not in other populations. In this study, individuals from diverse populations with RSTS were assessed by clinical examination and facial analysis technology. Clinical data of 38 individuals from 14 different countries were analyzed. The median age was 7 years (age range: 7 months to 47 years), and 63% were females. The most common phenotypic features in all population groups included broad thumbs and/or halluces in 97%, convex nasal ridge in 94%, and arched eyebrows in 92%. Face images of 87 individuals with RSTS (age range: 2 months to 47 years) were collected for evaluation using facial analysis technology. We compared images from 82 individuals with RSTS against 82 age- and sex-matched controls and obtained an area under the receiver operating characteristic curve (AUC) of 0.99 (p < .001), demonstrating excellent discrimination efficacy. The discrimination was, however, poor in the African group (AUC: 0.79; p = .145). Individuals with EP300 variants were more effectively discriminated (AUC: 0.95) compared with those with CREBBP variants (AUC: 0.93). This study shows that clinical examination combined with facial analysis technology may enable earlier and improved diagnosis of RSTS in diverse populations.

Mowat-Wilson syndrome in a Chinese population: A case series.

Mowat-Wilson syndrome (MWS) is characterized clinically by a distinctive facial gestalt, intellectual disability, microcephaly, epilepsy, and nonobligatory congenital malformations such as Hirschsprung disease, urogenital anomalies, congenital heart disease, eye malformations. This article summarized the clinical features and molecular findings of 15 Chinese MWS patients. The results revealed a higher incidence of congenital heart disease in Chinese MWS patients compared to that previously reported in Caucasian cohorts, while the incidence of Hirschsprung disease and genitourinary malformation appeared to be lower. This suggests possible ethnicity-related modifying effects in the MWS phenotype.

A case of G1013R FBN1 mutation: A potential genotype-phenotype correlation in severe Marfan syndrome.

Marfan Syndrome (MFS) is an autosomal dominant connective tissue disorder with a wide range of severities. Ninety-five percent of MFS probands have a mutation in the fibrillin-1 gene (FBN1); however, there are a high number of unique mutations complicating attempts at establishing any phenotype-genotype correlations for this disease (Tiecke et al., European Journal of Human Genetics, 2001, 9, 13-21). One of the few extant genotype-phenotype correlations is in exon 24-32 which have been associated with a severe pediatric presentation of neonatal MFS with predominately cardiovascular symptoms. We present a 24-year-old male patient with a heterozygous de novo variant NM_000138.4: c.3037G>A (p.G1013R) located in exon 25 of the FBN1 gene. The patient was found to have dysplastic mitral and tricuspid valves with dilated aortic root at 9 months of age. This is a notable case in that the location of this patient's mutation and his age of symptom onset would indicate a guarded prognosis. Further, this mutation, FBN1 G1013R, has been reported in the literature in four other unrelated patients all of whom presented at a young age with cardiac involvement and all of whom had relative longevity when compared to other patients with mutations in this exon 24-32 hot spot. These findings may represent a more specific genotype-phenotype correlation within this mutational hot spot.

CHARGE syndrome in nine patients from China.

CHARGE syndrome (CS) is a multiple congenital anomalies condition with the majority of cases caused by dominant loss-of-function mutations of the CHD7 gene. It is clinically characterized by coloboma of the eyes, heart defects, choanal atresia, retardation of growth and/or development, genital and/or urinary anomalies and ear malformations associated with deafness and vestibular disorder(s). This case series reported nine molecularly confirmed Chinese CS patients from nine unrelated families in Hong Kong. Clinical phenotype and facial features of these nine Chinese CS patients together with four previously reported Chinese patients were reviewed. Typical presentations like coloboma and choanal atresia were not universally present. The prevalence of choanal atresia in these Chinese CS patients was found to be significantly lower than that in previous cohorts of other ethnic groups. This report highlighted the existence of phenotypic variation of CS among different ethnicities and suggested that a high index of suspicion is necessary for diagnosis of CS in Chinese patients.

Coffin-Lowry syndrome in Chinese.

Coffin-Lowry syndrome (CLS) is a well-described syndrome characterized by intellectual disability, growth retardation, recognizable dysmorphic features, and skeletal changes. It is an X-linked syndrome where males are more severely affected and females have high variability in clinical presentations. This case series reports nine molecularly confirmed Chinese CLS patients from six unrelated families (three with familial variants and three with de novo variants). There is a wide genotypic spectrum with five novel variants in RPS6KA3 gene. Clinical phenotype and facial features of these Chinese CLS patients are comparable to what has been described in other ethnicities.

Genetic landscape of RASopathies in Chinese: Three decades' experience in Hong Kong.

RASopathies are a group of genetic disorders due to dysregulation of the RAS-MAPK signaling pathway, which is important in regulating cell growth, proliferation, and differentiation. These include Noonan syndrome (NS), Noonan syndrome with multiple lentigines (NSML), cardiofaciocutaneous (CFC) syndrome, and Costello syndrome (CS), clinical manifestations include growth retardation, developmental delay, cardiac defects, and specific dysmorphic features. There were abundant publications describing the genotype and phenotype from the Western populations. However, detailed study of RASopathies in Chinese population is lacking. We present here the largest cohort of RASopathies ever reported in Chinese populations, detailing the mutation spectrum and clinical phenotypes of these patients. The Clinical Genetic Service, Department of Health, and Queen Mary Hospital are tertiary referral centers for genetic disorders in Hong Kong. We retrospectively reviewed all the genetically confirmed cases of RASopathies, including NS, NSML, CFC syndrome, and CS, over the past 29 years (from 1989 to 2017). Analyses of the mutation spectrum and clinical phenotypes were performed. One hundred and ninety-one ethnic Chinese patients with genetically confirmed RASopathies were identified, including 148 patients with NS, 23 NSML, 12 CFC syndrome, and eight CS. We found a lower incidence of hypertrophic cardiomyopathy in individuals with NSML (27.3%), and NS caused by RAF1 mutations (62.5%). Another significant finding was for those NS patients with myeloproliferative disorder, the mutations fall within Exon 3 of PTPN11 but not only restricted to the well-known hotspots, that is, p.Asp61 and p.Thr731, which suggested that re-evaluation of the current tumor surveillance recommendation maybe warranted.

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

Chromosomal microarray (CMA) is recommended as a first tier investigation for patients with developmental delay (DD), intellectual disability (ID), autistic spectrum disorder (ASD), and multiple congenital anomalies (MCA). It is widely used in the prenatal and postnatal settings for detection of chromosomal aberrations. This is a retrospective review of all array comparative genomic hybridization (aCGH/ array CGH) findings ascertained in two major prenatal and postnatal genetic diagnostic centers in Hong Kong from June 2012 to December 2017. Medical records were reviewed for cases with pathogenic and variants of uncertain clinical significance (VUS). Classification of copy number variants (CNVs) was based on current knowledge and experience by August 2018. The aims of this review are to study the diagnostic yield of array CGH application in prenatal and postnatal settings in Hong Kong and to describe the spectrum of abnormalities found. Prenatal indications included abnormal ultrasound findings, positive Down syndrome screening, abnormal noninvasive prenatal test results, advanced maternal age and family history of chromosomal or genetic abnormalities. Postnatal indications included unexplained DD, ID, ASD, and MCA. A total of 1,261 prenatal subjects and 3,096 postnatal patients were reviewed. The prenatal diagnostic yield of pathogenic CNV and VUS (excluding those detectable by karyotype) was 3.5%. The postnatal diagnostic yield of pathogenic CNV was 15.2%. The detection rates for well-defined microdeletion and microduplication syndromes were 4.6% in prenatal and 6.1% (1 in 16 index patients) in postnatal cases, respectively. Chromosomes 15, 16, and 22 accounted for over 21 and 25% of pathogenic CNVs detected in prenatal and postnatal cohorts, respectively. This review provides the first large scale overview of genomic imbalance of mostly Chinese patients in prenatal and postnatal settings.