OBJECTIVE:Prenatal cell-free DNA screening is widely used to assess the risk of fetal trisomy 21, 18, and 13. Although commercial and laboratory-developed tests (LDTs) show high accuracy in validation studies, real-world longitudinal performance data are lacking. METHOD:In Belgium, prenatal cell-free DNA screening is a population screening offered to all pregnant people, regardless of their a priori risk. Over 3 years, all confirmatory diagnostic tests after a positive prenatal cell-free DNA screening result were recorded along with the technologies used and their outcomes. Positive predictive values (PPVs) for the three common fetal trisomies were calculated per technology. RESULTS:A total of 1158 diagnostic tests were performed after a positive prenatal cell-free DNA screening. Of these, 58.5% came from an LDT, 15.7% from VeriSeq (Illumina), 6.6% from Harmony (Roche), 5% from Vanadis (Perkin-Elmer); for 14.2% the technology could not be traced. PPVs ranged from 92.2% to 65.7% for trisomy 21, from 82.8% to 44.4% for trisomy 18, and from 40% to 18.2% for trisomy 13. Overall, the LDT performed better than the commercial tests. CONCLUSION:This study confirms the reported accuracy of commercial tests and LDT, while showing that LDT generally outperforms commercial tests. Despite high specificities across tests, differences in PPVs significantly impact pregnant people and the national health care system.

An international workshop was held in Leuven, Belgium, on June 19–20, 2023, to discuss the communication of genetic risk information within families in the context of personalized prevention. Organized as part of the Horizon Europe project PROPHET (PeRsOnalised Prevention roadmap for the future HEalThcare in Europe), the event gathered interdisciplinary stakeholders to explore the benefits and challenges of various policy approaches for returning genetic test results with implications for family members. Five key themes emerged from the discussions: (1) recognizing family communication as an ongoing process, (2) adopting a family-centered approach rather than an individual one, (3) clarifying roles and responsibilities in the communication process, (4) addressing the lack of clear guidelines and policies, and (5) ensuring sufficient resources. To enhance family communication of genetic risk information, participants emphasized the importance of improving pre-test counseling and follow-up procedures, implementing policies to clarify roles and responsibilities, and providing training for healthcare professionals both within and outside genetic services.

An international workshop was held in Leuven, Belgium, on June 19–20, 2023, to discuss the communication of genetic risk information within families in the context of personalized prevention. Organized as part of the Horizon Europe project PROPHET (PeRsOnalised Prevention roadmap for the future HEalThcare in Europe), the event gathered interdisciplinary stakeholders to explore the benefits and challenges of various policy approaches for returning genetic test results with implications for family members. Five key themes emerged from the discussions: (1) recognizing family communication as an ongoing process, (2) adopting a family-centered approach rather than an individual one, (3) clarifying roles and responsibilities in the communication process, (4) addressing the lack of clear guidelines and policies, and (5) ensuring sufficient resources. To enhance family communication of genetic risk information, participants emphasized the importance of improving pre-test counseling and follow-up procedures, implementing policies to clarify roles and responsibilities, and providing training for healthcare professionals both within and outside genetic services.

The systematic reimbursement of non-invasive prenatal testing (NIPT) in Belgium has led to earlier diagnoses of fetal sex discordance. Variations in sex differentiation may be isolated or associated with more complex syndromic etiologies. Some genetic conditions necessitate prenatal diagnosis and early management, while other conditions do not require invasive prenatal testing. Thereby, implementation of diagnostic algorithms has become essential for the management of conditions underlying fetal sex discordance, to optimize obstetric follow-up and immediate neonatal care. Healthcare systems in each country should also be considered in these practical recommendations. This article proposes a decision tree for the management of fetal sex discordance with NIPT in Belgium, as illustrated by a clinical report of a newborn presenting a diagnosis of mixed gonadal dysgenesis.

Introduction:Heterozygous pathogenic variants in MYH3 are known to be responsible for distal arthrogryposis. Case report:We report a consanguineous family of four children with two likely pathogenic MYH3 homozygous variants associated with complex movement disorders, especially prominent lingual dystonia, along with skeletal abnormalities. The two variants in MYH3 (c.3445G>A and c.4760T>C) have already been described in patients with congenital arthrogryposis. No other significant variation was found using long-read whole genome sequencing. Discussion:We have extended the phenotype of MYH3-associated arthrogryposis to include movement disorders, which may have been underdiagnosed to date. Highlights:This article extends the phenotype of MYH3-associated arthrogryposis to include movement disorders, illustrating a family of four children presenting MYH3 skeletal disorders and lingual dystonia. Two homozygous likely pathogenic variants have been identified in the four sibs and appear to be causative for both skeletal and neurological phenotypes.

The rapid development of therapies for severe and rare genetic conditions underlines the need to incorporate first-tier genetic testing into newborn screening (NBS) programs. A workflow was developed to screen newborns for 165 treatable pediatric disorders by deep sequencing of regions of interest in 405 genes. The prospective observational BabyDetect pilot project was launched in September 2022 in a maternity ward of a public hospital in the Liege area, Belgium. In this ongoing observational study, 4,260 families have been informed of the project, and 3,847 consented to participate. To date, 71 disease cases have been identified, 30 of which were not detected by conventional NBS. Glucose-6-phosphate dehydrogenase deficiency was the most frequent disorder detected, with 44 positive individuals. Of the remaining 27 cases, 17 were recessive disorders. We also identified one false-positive case in a newborn in whom two variants in the AGXT gene were identified, which were subsequently shown to be located on the maternal allele. Nine heterozygous variants were identified in genes associated with dominant conditions. Results from the BabyDetect project demonstrate the importance of integrating biochemical and genomic methods in NBS programs. Challenges must be addressed in variant interpretation within a presymptomatic population and in result reporting and diagnostic confirmation. The BabyDetect project offered expanded newborn genomic screening covering more than 400 genes to 4,260 families, leading to 71 clinical diagnoses.

Shprintzen-Goldberg syndrome is a rare systemic connective tissue disorder caused by heterozygous mutations in the Sloan-Kettering Institute (SKI) gene. The clinical presentation is reminiscent of Marfan and Loeys-Dietz syndromes, making differential diagnosis challenging. Shprintzen-Goldberg syndrome’s distinctive features are craniosynostosis and learning disabilities. The pathophysiology of these three conditions is similar as they all result in the deregulation of the transforming growth factor beta (TGF-β) signaling pathway and thus an altered expression of TGF-β responsive genes.We report a family of two patients: one with initial suspicion of hypermobile Ehlers-Danlos syndrome and the second with suspicion of Marfan syndrome, as the Marfan systemic score was positive and no craniosynostosis or learning disabilities were described. They were diagnosed with Shprintzen-Goldberg syndrome after a heterozygous probably pathogenic variant in the second mutational hotspot of SKI Dachshund homology domain was identified.We reviewed the genotype-phenotype correlation among the three mutational hotspots in SKI: the amino acids 20 to 35 of the receptor-regulated small mothers against decapentaplegic domain (group 1, n=32), amino acids 94 to 117 of Dachshund homology domain (group 2, n=12), and threonine 180 of Dachshund homology domain (group 3, n=11 including our patients).As the main differential diagnoses of Shprintzen-Goldberg syndrome are Marfan and Loeys-Dietz syndromes, we completed the comparison already made by Loeys et al. (2018) of Shprintzen-Goldberg syndrome clinical features among the different mutational hotspots with Marfan syndrome and the different types of Loeys-Dietz syndrome.In addition to the already described absence of learning disabilities in Shprintzen-Goldberg patients with a pathogenic variant in the threonine 180 of Dachshund homology domain, facial features also appeared to be less severe. The clinical overlap with Marfan and Loeys-Dietz patients requires genetic testing in order to establish an accurate molecular diagnosis at the variant level, and to adapt genetic counseling and clinical management.

Background: Shprintzen-Goldberg syndrome (SGS) is a rare systemic connective tissue disorder with a clinical presentation reminiscent of both Marfan syndrome (MF) and Loeys-Dietz syndrome (LDS). This makes differential diagnosis challenging, SGS distinctive features being craniosynostosis and learning disabilities. SGS is caused by a heterozygous mutation in the SKI gene. Three mutational hotspots have been described.

Rapid Whole Genome Sequencing (rWGS) represents a valuable exploration in critically ill pediatric patients. Early diagnosis allows care to be adjusted. We evaluated the feasibility, turnaround time (TAT), yield, and utility of rWGS in Belgium. Twenty-one unrelated critically ill patients were recruited from the neonatal intensive care units, the pediatric intensive care unit, and the neuropediatric unit, and offered rWGS as a first tier test. Libraries were prepared in the laboratory of human genetics of the University of Liège using Illumina DNA PCR-free protocol. Sequencing was performed on a NovaSeq 6000 in trio for 19 and in duo for two probands. The TAT was calculated from the sample reception to the validation of results. Clinical utility data were provided by treating physicians. A definite diagnosis was reached in twelve (57.5%) patients in 39.80 h on average (range: 37.05–43.7). An unsuspected diagnosis was identified in seven patients. rWGS guided care adjustments in diagnosed patients, including a gene therapy, an off-label drug trial and two condition-specific treatments. We successfully implemented the fastest rWGS platform in Europe and obtained one of the highest rWGS yields. This study establishes the path for a nationwide semi-centered rWGS network in Belgium.

(Abstracted from Genet Med 2022;24:344–363) Approximately 2% to 3% of pregnancies are affected by fetal abnormalities, and many of these are detected by ultrasound. After identification of suspected fetal structural anomaly, invasive procedures such as chorionic villus sampling and amniocentesis are offered as a method of prenatal genetic diagnosis.

A 13-year-old girl with Jervell and Lange-Nielsen syndrome associated congenital long QT syndrome (LQTS) and central deafness was admitted for generalized seizures. LQTS had been diagnosed after birth and confirmed at genetic testing. β-blocker treatment was immediately started. Despite this, since the age of 12 months, recurrent cerebral seizures occurred leading to the diagnosis of epilepsy. Anti-convulsive therapy was initiated but without success. At the last admission, nadolol dosage seemed infratherapeutic. Considering malignant ventricular arrhythmias as the cause of seizures, the β-blocker dosage was adjusted to weight and levels of magnesium and potassium optimized. Furthermore, the patient received an implantable Medtronic Reveal LINQ Recorder®. Since then, the adolescent has been asymptomatic with no arrhythmia documented. LQTS is due to one or more mutations of genes coding for ion channels. It may induce malignant ventricular arrhythmias and is a major cause of sudden cardiac death in children. Generalized cerebral seizures are extra-cardiac manifestations caused by decreased cerebral perfusion during ventricular arrhythmia. They are commonly misinterpreted as manifestations of epilepsy. For any patient with known or unknown LQTS who presents seizures with resistance to anti-convulsive therapy, a cardiac electrophysiological investigation should be performed promptly to ensure etiological diagnosis and optimize treatment.

Purpose The variant spectrum and the phenotype of X-linked Kabuki syndrome type 2 (KS2) are poorly understood. Methods Genetic and clinical details of new and published individuals with pathogenic KDM6A variants were compiled and analyzed. Results Sixty-one distinct pathogenic KDM6A variants (50 truncating, 11 missense) from 80 patients (34 males, 46 females) were identified. Missense variants clustered in the TRP 2, 3, 7 and Jmj-C domains. Truncating variants were significantly more likely to be de novo. Thirteen individuals had maternally inherited variants and one had a paternally inherited variant. Neonatal feeding difficulties, hypoglycemia, postnatal growth retardation, poor weight gain, motor delay, intellectual disability (ID), microcephaly, congenital heart anomalies, palate defects, renal malformations, strabismus, hearing loss, recurrent infections, hyperinsulinism, seizures, joint hypermobility, and gastroesophageal reflux were frequent clinical findings. Facial features of over a third of patients were not typical for KS. Males were significantly more likely to be born prematurely, have shorter stature, and severe developmental delay/ID. Conclusion We expand the KDM6A variant spectrum and delineate the KS2 phenotype. We demonstrate that the variability of the KS2 phenotypic depends on sex and the variant type. We also highlight the overlaps and differences between the phenotypes of KS2 and KS1.

OBJECTIVE: To evaluate the accuracy and diagnostic value of genome-wide noninvasive prenatal testing (NIPT) for the detection of fetal aneuploidies in multiple gestations, with a focus on dichorionic-diamniotic twin pregnancies. METHODS: We performed a retrospective cohort study including data from pregnant women with a twin or higher-order gestation who underwent genome-wide NIPT at one of the eight Belgian genetic centers between November 1, 2013, and March 1, 2020. Chorionicity and amnionicity were determined by ultrasonography. Follow-up invasive testing was carried out in the event of positive NIPT results. Sensitivity and specificity were calculated for the detection of trisomy 21, 18, and 13 in the dichorionic-diamniotic twin cohort. RESULTS: Unique NIPT analyses were performed for 4,150 pregnant women with a multiple gestation and an additional 767 with vanishing gestations. The failure rate in multiple gestations excluding vanishing gestations ranged from 0% to 11.7% among the different genetic centers. Overall, the failure rate was 4.8%, which could be reduced to 1.2% after single resampling. There were no common fetal trisomies detected among the 86 monochorionic-monoamniotic and 25 triplet cases. Two monochorionic-diamniotic twins had an NIPT result indicative of a trisomy 21, which was confirmed in both fetuses. Among 2,716 dichorionic-diamniotic twin gestations, a sensitivity of 100% (95% CI 74.12-100%) and a specificity of 100% (95% CI 99.86-100%) was reached for trisomy 21 (n=12). For trisomy 18 (n=3), the respective values were 75% (95% CI 30.06-95.44%) sensitivity and 100% (95% CI 99.86-100%) specificity, and for trisomy 13 (n=2), 100% (95% CI 20.65-100%) sensitivity and 99.96% (95% CI 99.79-99.99%) specificity. In the vanishing gestation group, 28 NIPT results were positive for trisomy 21, 18, or 13, with only five confirmed trisomies. CONCLUSION: Genome-wide NIPT performed accurately for detection of aneuploidy in dichorionic-diamniotic twin gestations.