Genetic Counseling Research Articles

Genetic analysis of a pedigree affected with Intellectual disability due to variants of two different genes

To explore the genetic etiology of a pedigree with intellectual disability and explore its pathogenesis. A Chinese pedigree which had presented at the Henan Provincial People's Hospital in March 2023 was selected as the study subject. Clinical data of the pedigree were collected, along with peripheral venous blood samples from its members. Whole exome sequencing (WES) was carried out, and candidate variants were verified by Sanger sequencing. Amniotic fluid was collected for prenatal diagnosis. This study was approved by the Medical Ethics Committee of the Henan Provincial People's Hospital (Ethics No. 2019-134). Both the proband (a 6-year-old male) and his mother (30 years old) had various degrees of intellectual and motor impairment. WES revealed that the proband has harbored a de novo heterozygous c.2563_2567dup (p.Lys856fs) variant of the UBE3A gene, while his mother, maternal grandmother and fetus had all harbored a novel heterozygous c.409+1G>A variant of the RNF13 gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), both variants were predicted to be pathogenic (PVS1+PS1+PM2_Supporting; PVS1+PM2_Supporting+PP3). Based on the clinical manifestations and the result of genetic testing, the heterozygous c.2563_2567dup (p.Lys856fs) variant of the UBE3A gene probably underlay the intellectual disability and developmental delay in the proband, whilst the heterozygous c.409+1G>A variant of the RNF13 gene may underlie the intellectual disability in the proband's mother and grandmother. Above results have enabled genetic counseling and prenatal diagnosis for this pedigree.

Methylation epigenetic analysis of a pedigree affected with Fragile X syndrome based on Nanopore long-read sequencing

To explore the genetic basis for a Chinese pedigree affected with Fragile X syndrome (FXS) through Nanopore long-read sequencing. A FXS pedigree who had undergone genetic counseling at the First Affiliated Hospital of Zhengzhou University in April 2023 was selected as the study subject. Nanopore long-read sequencing, triplet-repeat primed PCR (TP-PCR), methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and trinucleotide polymorphism genotyping of androgen receptor (AR) gene were used to analyze the FMR1 CGG repeat number, methylation, and X chromosome inactivation of the pedigree members. This study has been approved by the Medical Ethics Committee of the First Affiliated Hospital of Zhengzhou University (No. KS-2018-KY-36). Full mutation and CpG island hypermethylation were detected in the proband. The elder sister of the proband had full mutation of the FMR1 gene on one X chromosome and hypermethylation of CpG island, while the FMR1 gene on the other X chromosome was normal. FMR1 premutation was detected in the proband's mother. Nanopore long-read sequencing can simultaneously detect the dynamic mutation and methylation status of the FMR1 gene on the two X chromosomes of females, which has important value for the diagnosis of FXS in different genders.

Clinical features and genetic analysis of a child with Congenital disorder of glycosylation due to novel variants of COG6 gene

To analyze the clinical characteristics of a child with Congenital disorder of glycosylation due to compound heterozygous variants of COG6 gene (COG6-CDG). A child who was admitted to Xi'an Children's Hospital on January 10, 2023 was selected as the study subject. Clinical data were collected. Pathogenic variants were analyzed by whole exome sequencing, and candidate variants were verified by Sanger sequencing, in vitro experiments and bioinformatic analysis. This study was approved by the Medical Ethics Committee of Xi'an Children's Hospital (Ethics No. 20230101). The child, a 1-month-8-day-old male, was admitted for diarrhea and weight loss for one month. He had presented with cholestasis, diarrhea, facial dysmorphism, poor response, bilateral Simian crease, and brain atrophy. After discharge, he had continued to have high fever, feeding difficulty, and deceased finally. Whole exome sequencing results showed that he had harbored compound heterozygous variants of the COG6 gene, namely c.807delT (p.F269Lfs*37) and c.1746+1G>C (p.Gly565_Met582del). Sanger sequencing verified that the variants were inherited from his father and mother, respectively. In vitro experiments verified that the c.1746+1G>C variant could affect the mRNA splicing and produce a truncated protein, whilst the c.807delT variant could significantly reduce gene expression at both mRNA and protein levels. Based on the guidelines from the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP), the variants were classified as pathogenic (PVS1+PM3+PM2_Supporting) and likely pathogenic (PVS1+PM2_Supporting), respectively. The c.807delT (p.F269Lfs*37) and c.1746+1G>C (p.Gly565_Met582del) compound heterozygous variants of the COG6 gene probably underlay the pathogenesis of this child. Above finding has enriched the mutational spectrum of COG6-CDG and provided a basis for the genetic counseling for this family.

Segregation of Trans Mutations in the CDH23 Gene in an Emirati Family with Sensorineural Hearing Loss.

Hearing loss (HL) is a significant global health concern, affecting approximately 1 in every 1000 newborns, with over half of these cases attributed to genetic factors. This study focuses on identifying the genetic basis of autosomal recessive non-syndromic hearing loss (ARNSHL) in a consanguineous Emirati family. Clinical exome sequencing (CES) was performed on affected members of the family, followed by Sanger sequencing to validate the findings. Specific primers were used for PCR amplification of target CDH23 exons. Mutations were analyzed using various computational tools to assess their pathogenicity. We identified two heterozygous mutations in the CDH23 gene: a novel nonsense variant (c.264G>A, p.Trp88Ter) and a missense variant (c.5168G>A, p.Arg1723His). Both mutations were found in trans configuration, suggesting a compound heterozygous state contributing to the phenotype. In silico analysis predicted a significant impact on protein function, potentially leading to the observed ARNSHL. This study emphasizes the complexity of genetic factors in hearing loss, particularly in highly consanguineous populations. The identification of both nonsense and missense mutations in the CDH23 gene enhances understanding of its role in hearing loss and provides essential insights for genetic counseling and future therapeutic strategies.

Genetic analysis of a child with Congenital insensitivity to pain due to compound heterozygous variants of SCN9A gene

To explore the genetic etiology of a child featuring multiple fractures and congenital insensitivity to pain (CIP). A child who had presented at the West China Hospital of Sichuan University on March 16, 2023 for recurrent fractures and CIP was selected as the study subject. Peripheral blood samples of the child and his parents was collected. Trio-whole exome sequencing was carried out. Candidate variants were verified by Sanger sequencing and bioinformatic analysis. This study has been approved by the Medical Ethics Committee of West China Hospital of Sichuan University (No. 2019-772). Trio-whole exome sequencing revealed that the child has harbored compound heterozygous variants of the SCN9A gene, namely c.560delC (p.P187Rfs*15) and c.829C>T (p.R277*), which were respectively inherited from his father and mother. Homozygous c.829C>T variant had been demonstrated as pathogenic among CIP patients, whilst the c.560delC (p.P187Rfs*15) variant was unreported previously and predicted to be pathogenic based on the guidelines of the American College of Medical Genetics and Genomics (ACMG). The child was diagnosed with CIP due to the compound heterozygous variants of the SCN9A gene. Above finding has enabled genetic counselling and reproductive guidance for this family.

Validation of a guidelines-based digital tool to assess the need for germline cancer genetic testing

BackgroundEfficient and scalable solutions are needed to identify patients who qualify for germline cancer genetic testing. We evaluated the clinical validity of a brief, patient-administered hereditary cancer risk assessment digital tool programmed to assess if patients meet criteria for germline genetic testing, based on personal and family history, and in line with national guidelines.MethodsWe applied the tool to cases seen in a nationwide telehealth genetic counseling practice. Validity of the tool was evaluated by comparing the tool’s assessment to that of the genetic counselor who saw the patient. Patients’ histories were extracted from genetic counselor-collected pedigrees and input into the tool by the research team to model how a patient would complete the tool. We also validated the tool’s assessment of which specific aspects of the personal and family history met criteria for genetic testing. Descriptive statistics were used.ResultsOf the 152 cases (80% female, mean age 52.3), 56% had a personal history of cancer and 66% met genetic testing criteria. The tool and genetic counselor agreed in 96% of cases. Most disagreements (4/6; 67%) occurred because the genetic counselor’s assessment relied on details the tool was not programmed to collect since patients typically don’t have access to the relevant information (pathology details, risk models). We also found complete agreement between the tool and research team on which specific aspects of the patient’s history met criteria for genetic testing.ConclusionWe observed a high level of agreement with genetic counselor assessments, affirming the tool’s clinical validity in identifying individuals for hereditary cancer predisposition testing and its potential for increasing access to hereditary cancer risk assessment.

Using Social Robots and AI to Perform Genetic Risk Assessment for Cancer

Genetic risk assessment (GRA) and genetic counseling have become integral to optimal patient care for patients with cancer. At present, there is a limited number of qualified healthcare providers who provide this service. To assist professionals in the GRA process, we have combined social robotics and retrieval-augmented generative artificial intelligence (RAG AI) to provide education related to hereditary cancer to be included in GRA sessions for individuals at risk. This GRA application pushes the boundary on previously available chatbots and AI systems by creating a novel and interactive experience enhanced by professionally verified information. In the future, we seek to improve the app as it is and obtain feedback from both GRA professionals and potential end-users that will be used to enhance the system and provide customized risk assessment. Overall, our GRA system takes the next step towards informing patients of their hereditary cancer risk and pertinent care options.

Developmental and Epileptic Encephalopathies: Need for Bridging the Gaps Between Clinical Syndromes and Underlying Genetic Etiologies.

Advancement in genetic testing has become increasingly important in diagnosing and managing developmental and epileptic encephalopathies (DEEs), a group of rare neurodevelopmental disorders characterized by early-onset seizures, developmental delay, and electroencephalographic (EEG) abnormalities. These early epileptic encephalopathies are often described as various syndromes as per their clearly defined, relatively uniform, and distinct clinical phenotypes with consistent EEG and/or neuroimaging findings. Finding the underlying molecular mechanisms can cause a definitive change in the management strategy. With the evolving overlapping phenotypes, advent of technologies, and discovery of new genes, it is exceedingly becoming challenging to correctly characterise these disorders and plan subsequent evidence-based management. Cytogenetic microarray (CMA) and next generation sequencing (NGS) with improved data analysis pipe-lines and algorithms have revamped the diagnostic yield dramatically. However, as of now, there is a big lacuna in step-wise evaluation guideline or consensus on integration of genetic testing results with management plan. Understanding the genetic etiologies of such syndromes timely has three major implications: (1) Knowing the outcome of such a syndrome, (2) Therapeutic implications including licensing of drugs for certain forms (e.g. genetic syndromes involving ion channels) and (3) Genetic counseling, prenatal testing and choosing reproductive options in future pregnancies in such families. The focus of this review is to provide an understanding of different types of causative variants and their step-wise genetic testing approach; the most pressing clinical need and to develop an optimal diagnostic pathway for this group of patients.

Awareness, use, motivations and methods of accessing genetic testing in 2022 in the United States.

Awareness, access, and use of clinical and direct-to-consumer (DTC) genetic tests has increased in recent years with documented disparities in these services. We provide updated data on test awareness and use, and report novel data on motivations and methods for accessing genetic tests. Nationally representative data from the 2022 Health Information National Trends Survey (HINTS 6) were used to assess awareness and use of ancestry, personal trait, specific disease, and carrier testing by sociodemographic characteristics, examine reasons for undergoing tests, and methods of accessing them. Overall, 81.4% of respondents were aware and 40.0% had undergone testing. Only 10% of tests were ordered by genetic counselors, 80% of carrier and 65% of specific disease tests were ordered by other healthcare providers. Understanding family history was the most common reason for undergoing ancestry (72.2%) or personal trait tests (64.9%) whereas reasons such as doctor's recommendation (53%-59%), learning more about disease risk (18%-50%), and carrier testing (76%) were common for undergoing disease risk tests and carrier tests. In contrast to ancestry, personal trait, and carrier testing, there were no racial, ethnic, income, or rural/urban difference in use of specific disease risk testing. Diffusion of genetic tests into US society, although incremental, has made sizable increases in awareness, equitable use of specific disease tests but worsening socioeconomic inequality in DTC genetic test use. The study provides update on the state of genetic testing in the US and identifies groups that may need help accessing clinical genomic information and services.

Genetic correlation between fetal nuchal translucency thickening and cystic hygroma and exploration of pregnancy outcome

Chromosome microarray analysis (CMA) and whole exome sequencing (WES) are increasingly utilized in prenatal diagnosis of abnormal ultrasound findings, but studies on correlation between pathogenic copy number variations (pCNVs) and single-gene mutations in fetuses with nuchal translucency (NT) thickening/cystic hygroma (CH), and pregnancy outcomes, are rare. This study aimed to investigate clinical value of CMA and WES for NT thickening/CH in fetuses, explore genetic correlation between fetal NT thickening and CH, and analyze pregnancy outcomes. We retrospectively selected 215 pregnant women diagnosed with fetal NT thickening (NT > 95th)/CH who underwent invasive prenatal diagnosis at our hospital from January 2020 to June 2022. With negative chromosomal karyotype analysis (KA) and CMA results, patients voluntarily underwent WES. Patients were grouped by NT thickening/CH, and application value of KA, CMA, and WES examined. Ultrasound findings, pregnancy outcomes, and fetal growth post-birth were followed during mid/late pregnancy and post-delivery. Abnormalities in chromosomal number were detected in 28 of 215 samples, with a detection rate of 13.0%, and pCNVs were detected in 12 cases, with a detection rate of 5.6%. The most common abnormality in fetuses from both groups suggested by CMA was 22q11.21 microdeletion-microduplication syndrome. 35 patients with negative KA and CMA results underwent WES, and single gene variants were detected in 12 fetuses, with an abnormality rate of 34.3%. The incidence of adverse pregnancy outcomes was 28.2% in the NT thickening group and 82.9% in the CH group (P < 0.05). Overall, fetal NT thickening/CH was associated with genetic abnormalities, WES further improved the diagnosis of abnormal fetuses after negative KA and CMA results in both groups, and the incidence of adverse pregnancy outcomes was lower in the NT thickening group than in the CH group. The management of pregnancy outcomes could guide clinical genetic counselling.

How the prospect of a clinical trial impacts decision-making for predictive genetic testing in ALS

Objective: Genetic testing practices are rapidly evolving for people living with, or at-risk for, amyotrophic lateral sclerosis (ALS), due to emerging genotype-driven therapies. This study explored how individuals at-risk for familial ALS (fALS) perceive the opportunity to participate in a clinical trial, and to better understand how that may influence the decision-making process for predictive genetic testing. Methods: This study used both quantitative and qualitative data analyses. Data were collected through an online questionnaire, followed by semi-structured interviews conducted with twelve (n = 12) individuals at-risk for either SOD1- or C9orf72-ALS who had predictive testing prior to study participation. Interview data were analyzed using reflexive thematic analysis. Results: Three overarching themes were conceptualized from the data: i) the psychosocial impact of fALS; ii) perspectives of at-risk individuals on research involvement; and iii) predictive genetic counseling and testing considerations. These results contribute perspectives of the lived experience to inform predictive genetic counseling and testing practices for individuals at-risk for fALS. Conclusion: Individuals at-risk for fALS view potential participation in a presymptomatic clinical trial as an actionable measure that may increase their desire for predictive genetic testing. Genetic counseling was identified as a critical component of the predictive testing process given the life-changing implications associated with a positive result. Increased access to predictive genetic counseling, and in a timely manner, is a significant need in the ALS population given potential access to gene-specific therapies in the presymptomatic stage.

Ballooning and Bursting of Barrels and Pipes: A Rare Case of Suspected Vascular Ehlers–Danlos Disease

Vascular Ehler–Danlos disease (vEDS), a rare subtype of a rare disease, is a life-threatening disease, with an increased risk for spontaneous vascular or visceral rupture. These patients have fatal complications ranging from vascular aneurysms, dissection, and rupture of systemic vessels to frequent thromboembolic events, the common causes of death in these individuals with a shortened life span. In the present case, a 28-year-old male with history of shoulder dislocations and spontaneous colon perforation presented to the primary care clinic with right lower extremity swelling and pain. His history includes presentation to the emergency department with left lower leg swelling with compartment syndrome one year prior. A CT angiogram of lower extremities and abdomen revealed acute arterial extravasation of the left posterior tibial artery, indicating a ruptured aneurysm along with aneurysms of the splenic artery and left common iliac artery. He was treated with a saphenous vein graft, but was associated with post-operative complications that necessitated below-knee amputation. CT angiogram of his right leg revealed occlusion of the anterior tibial and peroneal arteries with aneurysms, and, ultimately, he was referred to a tertiary care center for aneurysm embolization. This case report emphasizes the frequent vascular complications encountered in vascular EDS patients, and thus advocates for close and regular monitoring for early referral and surgical management of their vascular anomalies. Finally, genetic counseling and screening of asymptomatic family members should be routinely implemented in these patients.

The distribution of regions of homozygosity (ROH) among consanguineous populations-implications for a routine genetic counseling service.

Regions of homozygosity (ROH) increase the risk of recessive disorders, and guidelines recommend reporting of excessive ROH in prenatal testing. However, ROH are common in populations that practice endogamy or consanguinity, and cutoffs for reporting ROH in such populations may not be evidence-based. We reviewed prenatal testing results (based on cytogenetic microarrays) from 2191 pregnancies in the Jewish and non-Jewish populations of Northern Israel and estimated the prevalence of ROH according to self-reported ethnicity and parental relationships. The proportion of the genome in ROH, ROH rate, was higher in non-Jews [Mean (SD) = 2.91% (3.92%); max = 25.54%; N = 689] than in Jews [Mean (SD) = 0.81% (0.49%); max = 3.93%; N = 1502]. In the non-Jewish populations, consanguineous marriages had the highest ROH rates [Mean (SD) = 7.14% (4.55%), N = 217], followed by endogamous [Mean (SD) = 1.13% (1.09%), N = 283] and non-endogamous [Mean (SD) = 0.69%(0. 56%), N = 189] marriages. ROH rates were greater than 5%, the ACMG-recommended cutoff, in 149/689 (21.63%) of the non-Jewish samples. Within the Jewish populations, the rates were similar between Ashkenazi, North African, and Middle Eastern Jews, but were higher for six consanguineous unions [Mean (SD) = 2.38% (1.23%)] and when spouses belonged to the same sub-population. Given the high ROH rates we observed in some subjects, we suggest that assessing the risk for recessive conditions in consanguineous/endogamous populations should be done before the first pregnancy, through genetic counseling and sequencing. Such an approach will: (1) identify couples who are at risk and counsel them on reproductive options; and (2) avoid the stress that couples who are not at risk may experience due to a prenatal ROH report.

DNAH3 deficiency causes flagellar inner dynein arm loss and male infertility in humans and mice

Axonemal protein complexes, including the outer and inner dynein arms (ODA/IDA), are highly ordered structures of the sperm flagella that drive sperm motility. Deficiencies in several axonemal proteins have been associated with male infertility, which is characterized by asthenozoospermia or asthenoteratozoospermia. Dynein axonemal heavy chain 3 (DNAH3) resides in the IDA and is highly expressed in the testis. However, the relationship between DNAH3 and male infertility is still unclear. Herein, we identified biallelic variants of DNAH3 in four unrelated Han Chinese infertile men with asthenoteratozoospermia through whole-exome sequencing (WES). These variants contributed to deficient DNAH3 expression in the patients’ sperm flagella. Importantly, the patients represented the anomalous sperm flagellar morphology, and the flagellar ultrastructure was severely disrupted. Intriguingly, Dnah3 knockout (KO) male mice were also infertile, especially showing the severe reduction in sperm movement with the abnormal IDA and mitochondrion structure. Mechanically, nonfunctional DNAH3 expression resulted in decreased expression of IDA-associated proteins in the spermatozoa flagella of patients and KO mice, including DNAH1, DNAH6, and DNALI1, the deletion of which has been involved in disruption of sperm motility. Moreover, the infertility of patients with DNAH3 variants and Dnah3 KO mice could be rescued by intracytoplasmic sperm injection (ICSI) treatment. Our findings indicated that DNAH3 is a novel pathogenic gene for asthenoteratozoospermia and may further contribute to the diagnosis, genetic counseling, and prognosis of male infertility.

DNAH3 deficiency causes flagellar inner dynein arm loss and male infertility in humans and mice.

Axonemal protein complexes, including the outer and inner dynein arms (ODA/IDA), are highly ordered structures of the sperm flagella that drive sperm motility. Deficiencies in several axonemal proteins have been associated with male infertility, which is characterized by asthenozoospermia or asthenoteratozoospermia. Dynein axonemal heavy chain 3 (DNAH3) resides in the IDA and is highly expressed in the testis. However, the relationship between DNAH3 and male infertility is still unclear. Herein, we identified biallelic variants of DNAH3 in four unrelated Han Chinese infertile men with asthenoteratozoospermia through whole-exome sequencing (WES). These variants contributed to deficient DNAH3 expression in the patients' sperm flagella. Importantly, the patients represented the anomalous sperm flagellar morphology, and the flagellar ultrastructure was severely disrupted. Intriguingly, Dnah3 knockout (KO) male mice were also infertile, especially showing the severe reduction in sperm movement with the abnormal IDA and mitochondrion structure. Mechanically, nonfunctional DNAH3 expression resulted in decreased expression of IDA-associated proteins in the spermatozoa flagella of patients and KO mice, including DNAH1, DNAH6, and DNALI1, the deletion of which has been involved in disruption of sperm motility. Moreover, the infertility of patients with DNAH3 variants and Dnah3 KO mice could be rescued by intracytoplasmic sperm injection (ICSI) treatment. Our findings indicated that DNAH3 is a novel pathogenic gene for asthenoteratozoospermia and may further contribute to the diagnosis, genetic counseling, and prognosis of male infertility.

'I Could Trust It': Experiences of Reciprocal Translocation Carriers and Their Partners With Prenatal Cell-Free DNA Screening for Unbalanced Translocations.

To explore the experiences of people having cfDNA screening to detect unbalanced translocations, and to understand motivations for choosing this option. We used a qualitative approach with in-depth semi-structured interviews with reciprocal translocation carriers and their partners. People who underwent cfDNA screening with translocation analysis through Victorian Clinical Genetics Services between 2015 and 2019 were invited to take part. Purposive sampling based on the participant's geographic location, requesting practitioner specialty and cfDNA screening result was used to capture a range of experiences. Interview transcripts were analysed using thematic analysis. Participants (n=13) had complex reproductive journeys associated with the translocation and opted for cfDNA screening rather than prenatal diagnosis to avoid risk to their pregnancy. Participants benefited from having a result early in pregnancy and had sufficient confidence in the result to decline a diagnostic testing procedure. Participants' experiences with cfDNA screening were intertwined with the experience of being a carrier of a reciprocal translocation. cfDNA screening with translocation analysis was perceived as an acceptable alternative to prenatal diagnosis and should be made more accessible to balanced translocation carriers. Access to specialist genetic counselling services is needed to ensure couples are provided with information about all prenatal testing options, including the benefits and limitations associated with cfDNA screening with translocation analysis.

Analysis of clinical phenotypes and genetic variations in two pedigrees affected with Weiss-Kruszka syndrome.

Weiss-Kruszka syndrome (WSKA) is a rare autosomal dominant syndrome characterized by multiple congenital anomalies caused by variants in the zinc finger protein 462 gene (ZNF462). About 40 cases of Weiss-Kruszka syndrome have been reported worldwide, and the aim of this study was to investigate the genetic causes of three patients from two Weiss-Kruszka syndrome family pedigrees with the aim of accumulating more data on the disease. To explore the clinical and genetic characteristics of two pedigrees with Weiss-Kruszka syndrome. The clinical data and family history of patients and family members of two pedigrees with Weiss-Kruszka syndrome were collected, and the pathogenic genes of the patients were analysed by whole-exon sequencing. Suspicious variants were verified by Sanger sequencing verification and bioinformatics prediction. Proband 1 has developmental delay, autistic behaviour, and abnormal electroencephalogram results. WES revealed a classical heterozygous c.6696-2A > C splice variant of the ZNF462 gene, which was detected in neither parent. This position was conserved, and the variant was predicted to be deleterious. Minigene assays revealed that three types of aberrantly spliced mRNAs were produced. MRI of proband 2 suggested dysplasia of the corpus callosum with the formation of hemispheric cleft cysts, with a teardrop-like appearance in the lateral ventricle. WES revealed that a heterozygous c.4891C > T:p. The Glu1631Ter nonsense variant of the ZNF462 gene was inherited from her mother. According to the guidelines of the American Society of Medical Genetics and combined with its clinical manifestations, c.6696-2A > C and c.4891C > T:p. Glu1631Ter was determined to be a possible pathogenic variant. The c.6696-2A>C and c.4891C > T:p.Glu1631Ter of the ZNF462 gene likely underlies Weiss-Kruszka syndrome in children (foetus), which enriches the variant spectrum of Chinese patients with Weiss-Kruszka syndrome and provides a basis for prenatal diagnosis and genetic counselling.

The Excess of Carriers in Rare Disorders Suggests a Nonpathogenic Effect for Most Variants of Uncertain Significance.

Functional annotation and interpretation of genetic variants are a critical step in genetic diagnosis, as it may lead to personalized therapeutic options and genetic counseling. While the number of confirmed pathogenic genetic variants in an individual is relatively low, the number of variants of uncertain significance (VOUS) can be considerably higher, increasing the number of potential carriers of genetic disorders. Thus, reducing uncertainty and assessing the real effect of VOUS are crucial for clinical and medical genetics. In this study, we evaluated the efficacy of genetic screening technologies in accurately predicting pathogenic variants and their corresponding disease prevalence in a cohort of over 6000 healthy individuals involved in assisted reproduction programs. Using data from 305 genes associated with recessive disorders, we determined the frequency of carriers of pathogenic variants and VOUS in our dataset and compared the predicted prevalence based on this information with reported population prevalence data. The higher predicted prevalence in some disorders when considering VOUS suggests a mostly benign effect.

Phenotypic Analysis of the HBA2: C.95 G > A Mutation in China

This study aimed to analyze the clinical phenotype of the HBA2: c.95G>A mutation in the Chinese population and to provide guidance for clinical diagnosis and genetic counseling. Peripheral blood samples were collected from 16 patients, including 6 newborns, 2 children, and 8 adults. Hematological parameters and hemoglobin electrophoresis were analyzed, and genotypes were identified using methods such as PCR combined with reverse dot blot (RDB), nested PCR, gap polymerase chain reaction (Gap-PCR), and DNA sequencing. The results showed that 10 patients had mild anemia, 2 had moderate anemia, and 12 exhibited microcytic hypochromic features with MCV values ranging from 53 to 74.7 fl and MCH values from 16.2 to 25.4 pg. Additionally, 3 cases displayed obvious HbH + HbBarts bands (>15%). Among the 16 cases, various combinations of the HBA2: c.95G>A mutation were observed: one case had –α3.7 combined with HBA2: c.95G>A, another had –α4.2 combined with HBA2: c.95G>A, and five had –SEA combined with HBA2: c.95G>A, while the remaining cases were HBA2: c.95G>A heterozygotes. The study concludes that the HBA2: c.95G>A mutation in the α2 globin gene causes α+ thalassemia. When this mutation is combined with the Southeast Asian deletion (–SEA), it results in HbH disease, characterized by moderate microcytic hypochromic anemia and the presence of HbH + HbBarts bands.

Genome-Wide, Non-Invasive Prenatal Testing for rare chromosomal abnormalities: A systematic review and meta-analysis of diagnostic test accuracy.

Genome-Wide Non-Invasive Prenatal Testing (GW-NIPT) can provide positive results not only for common autosomal aneuploidies but also for rare autosomal trisomies (RATs) and structural chromosomal abnormalities (StrCAs). Due to their rarity, there is currently insufficient information on positive predictive value PPV of RAT and StrCA-positive cases in the literature. In this study, the screening accuracy and pregnancy outcomes of cases positive for rare chromosomal abnormalities were examined based on publications in which GW-NIPT testing was performed. True positive cases were determined using two different methodologies. One was a confirmed methodology, where only cases validated by genetic testing were considered true positives with a definite diagnosis, and the other was an extended methodology, where, in addition to cases confirmed by genetic testing, intrauterine fetal death and termination of pregnancy due to an abnormality confirmed by ultrasound examination were also considered true positives, where no diagnosis had been made but the fetus was probably affected. Seventeen studies were analyzed, with a total GW-NIPT population of 740,076. Of these, 1,738 were RAT positive. Using the confirmed method, we found the highest rates of true positives in T16, followed by T22, and T2, using the extended method, the highest rate of true positives in T15, T16 and T22. This is the first meta-analysis to determine the frequency of rare chromosomal abnormalities, test-positive rates, and the PPV of each chromosomal abnormality with high precision. Our results could aid pre- and post-test genetic counselling and help patients and clinicians in their decision-making.