Extending the clinical spectrum of X-linked Tonne-Kalscheuer syndrome (TOKAS): new insights from the fetal perspective.

INTRODUCTION: Tonne-Kalscheuer syndrome (TOKAS) is a recessive X-linked multiple congenital anomaly disorder caused by RLIM variations. Of the 41 patients reported, only 7 antenatal cases were described. METHOD: After the antenatal diagnosis of TOKAS by exome analysis in a family followed for over 35 years because of multiple congenital anomalies in five male fetuses, a call for collaboration was made, resulting in a cohort of 11 previously unpublished cases. RESULTS: We present a TOKAS antenatal cohort, describing 11 new cases in 6 French families. We report a high frequency of diaphragmatic hernia (9 of 11), differences in sex development (10 of 11) and various visceral malformations. We report some recurrent dysmorphic features, but also pontocerebellar hypoplasia, pre-auricular skin tags and olfactory bulb abnormalities previously unreported in the literature. Although no clear genotype-phenotype correlation has yet emerged, we show that a recurrent p.(Arg611Cys) variant accounts for 66% of fetal TOKAS cases. We also report two new likely pathogenic variants in RLIM, outside of the two previously known mutational hotspots. CONCLUSION: Overall, we present the first fetal cohort of TOKAS, describe the clinical features that made it a recognisable syndrome at fetopathological examination, and extend the phenotypical spectrum and the known genotype of this rare disorder.

Growth charts in DYRK1A syndrome.

DYRK1A Syndrome (OMIM #614104) is caused by pathogenic variations in the DYRK1A gene located on 21q22. Haploinsufficiency of DYRK1A causes a syndrome with global psychomotor delay and intellectual disability. Low birth weight, growth restriction with feeding difficulties, stature insufficiency, and microcephaly are frequently reported. This study aims to create specific growth charts for individuals with DYRK1A Syndrome and identify parameters for size prognosis. Growth parameters were obtained for 92 individuals with DYRK1A Syndrome (49 males vs. 43 females). The data were obtained from pediatric records, parent reporting, and scientific literature. Growth charts for height, weight, body mass index (BMI), and occipitofrontal circumference (OFC) were generated using generalized additive models through R package gamlss. The growth curves include height, weight, and OFC measurements for patients aged 0-5 years. In accordance with the literature, the charts show that individuals are more likely to present intrauterine growth restriction with low birth weight and microcephaly. The growth is then characterized by severe microcephaly, low weight, and short stature. This study proposes growth charts for widespread use in the management of patients with DYRK1A syndrome.

1p36 deletion syndrome: Review and mapping with further characterization of the phenotype, a new cohort of 86 patients.

Chromosome 1p36 deletion syndrome (1p36DS) is one of the most common terminal deletion syndromes (incidence between 1/5000 and 1/10,000 live births in the American population), due to a heterozygous deletion of part of the short arm of chromosome 1. The 1p36DS is characterized by typical craniofacial features, developmental delay/intellectual disability, hypotonia, epilepsy, cardiomyopathy/congenital heart defect, brain abnormalities, hearing loss, eyes/vision problem, and short stature. The aim of our study was to (1) evaluate the incidence of the 1p36DS in the French population compared to 22q11.2 deletion syndrome and trisomy 21; (2) review the postnatal phenotype related to microarray data, compared to previously publish prenatal data. Thanks to a collaboration with the ACLF (Association des Cytogénéticiens de Langue Française), we have collected data of 86 patients constituting, to the best of our knowledge, the second-largest cohort of 1p36DS patients in the literature. We estimated an average of at least 10 cases per year in France. 1p36DS seems to be much less frequent than 22q11.2 deletion syndrome and trisomy 21. Patients presented mainly dysmorphism, microcephaly, developmental delay/intellectual disability, hypotonia, epilepsy, brain malformations, behavioral disorders, cardiomyopathy, or cardiovascular malformations and, pre and/or postnatal growth retardation. Cardiac abnormalities, brain malformations, and epilepsy were more frequent in distal deletions, whereas microcephaly was more common in proximal deletions. Mapping and genotype-phenotype correlation allowed us to identify four critical regions responsible for intellectual disability. This study highlights some phenotypic variability, according to the deletion position, and helps to refine the phenotype of 1p36DS, allowing improved management and follow-up of patients.

Psychomotor development in infants and young children with Down syndrome-A prospective, repeated measure, post-hoc analysis.

Children with Down syndrome (DS) show delayed acquisition of cognitive and functional skills compared to typically developing children. The objective of this study was to accurately describe early development of infants and young children (children hereafter) with DS based on a large recent sample. We carried out repeated measure analysis of the global development quotient (GDQ) and developmental age using data from the Assessment of Systematic Treatment with Folinic Acid and Thyroid Hormone on Psychomotor Development of Down Syndrome Young Children (ACTHYF) study (NCT01576705). Because there was no statistically significant difference in the primary endpoint between active treatment and placebo, data from all treatment groups were pooled for post-hoc analysis. Data of 141 children with DS aged 6-18 months at inclusion were analyzed. Mean GDQ decreased over the study period, especially in the youngest age classes ([6-9] and [9-12] months), indicating that acquisition of skills occurred at a slower pace compared to typically developing children. Strongest deficits were observed for motor and hearing and language skills. Only GDQ at baseline correlated significantly with evolution of GDQ. Future studies should aim at elucidating the mechanisms underlying motor and language development. Early pharmacological interventions together with early childhood therapies might be necessary to improve the developmental trajectory of children with DS.

De Novo Truncating Mutations in WASF1 Cause Intellectual Disability with Seizures.

Next-generation sequencing has been invaluable in the elucidation of the genetic etiology of many subtypes of intellectual disability in recent years. Here, using exome sequencing and whole-genome sequencing, we identified three de novo truncating mutations in WAS protein family member 1 (WASF1) in five unrelated individuals with moderate to profound intellectual disability with autistic features and seizures. WASF1, also known as WAVE1, is part of the WAVE complex and acts as a mediator between Rac-GTPase and actin to induce actin polymerization. The three mutations connected by Matchmaker Exchange were c.1516C>T (p.Arg506Ter), which occurs in three unrelated individuals, c.1558C>T (p.Gln520Ter), and c.1482delinsGCCAGG (p.Ile494MetfsTer23). All three variants are predicted to partially or fully disrupt the C-terminal actin-binding WCA domain. Functional studies using fibroblast cells from two affected individuals with the c.1516C>T mutation showed a truncated WASF1 and a defect in actin remodeling. This study provides evidence that de novo heterozygous mutations in WASF1 cause a rare form of intellectual disability.

ZMYND11-related syndromic intellectual disability: 16 patients delineating and expanding the phenotypic spectrum.

Pathogenic variants in ZMYND11, which acts as a transcriptional repressor, have been associated with intellectual disability, behavioral abnormalities, and seizures. Only 11 affected individuals have been reported to date, and the phenotype associated with pathogenic variants in this gene have not been fully defined. Here, we present 16 additional patients with predicted pathogenic heterozygous variants in including four individuals from the same family, to further delineate and expand the genotypic and phenotypic spectrum of ZMYND11-related syndromic intellectual disability. The associated phenotype includes developmental delay, particularly affecting speech, mild-moderate intellectual disability, significant behavioral abnormalities, seizures, and hypotonia. There are subtle shared dysmorphic features, including prominent eyelashes and eyebrows, a depressed nasal bridge with bulbous nasal tip, anteverted nares, thin vermilion of the upper lip, and wide mouth. Novel features include brachydactyly and tooth enamel hypoplasia. Most identified variants are likely to result in premature truncation and/or nonsense-mediated decay. Two ZMYND11 variants located in the final exon-p.(Gln586*) (likely escaping nonsense-mediated decay) and p.(Cys574Arg)-are predicted to disrupt the MYND-type zinc-finger motif and likely interfere with binding to its interaction partners. Hence, the homogeneous phenotype likely results from a common mechanism of loss-of-function.

Expanding the genetic and phenotypic relevance of KCNB1 variants in developmental and epileptic encephalopathies: 27 new patients and overview of the literature.

Developmental and epileptic encephalopathies (DEE) refer to a heterogeneous group of devastating neurodevelopmental disorders. Variants in KCNB1 have been recently reported in patients with early-onset DEE. KCNB1 encodes the α subunit of the delayed rectifier voltage-dependent potassium channel Kv 2.1. We review the 37 previously reported patients carrying 29 distinct KCNB1 variants and significantly expand the mutational spectrum describing 18 novel variants from 27 unreported patients. Most variants occur de novo and mainly consist of missense variants located on the voltage sensor and the pore domain of Kv 2.1. We also report the first inherited variant (p.Arg583*). KCNB1-related encephalopathies encompass a wide spectrum of neurodevelopmental disorders with predominant language difficulties and behavioral impairment. Eighty-five percent of patients developed epilepsies with variable syndromes and prognosis. Truncating variants in the C-terminal domain are associated with a less-severe epileptic phenotype. Overall, this report provides an up-to-date review of the mutational and clinical spectrum of KCNB1, strengthening its place as a causal gene in DEEs and emphasizing the need for further functional studies to unravel the underlying mechanisms.

Thyroid hormone and folinic acid in young children with Down syndrome: the phase 3 ACTHYF trial.

PURPOSE: To determine whether folinic acid (FA) and thyroxine, in combination or alone, benefit psychomotor development in young patients with Down syndrome (DS). METHODS: The Assessment of Systematic Treatment With Folinic Acid and Thyroid Hormone on Psychomotor Development of Down Syndrome Young Children (ACTHYF) was a single-center, randomized, double-blind, placebo-controlled phase 3 trial in DS infants aged 6-18 months. Patients were randomly assigned to one of four treatments: placebo, folinic acid (FA), L-thyroxine, or FA+L-thyroxine, administered for 12 months. Randomization was done by age and sex. The primary endpoint was adjusted change from baseline in Griffiths Mental Development Scale global development quotient (GDQ) after 12 months. RESULTS: Of 175 patients randomized, 143 completed the study. The modified intention-to-treat (mITT) population included all randomized patients who did not prematurely discontinue due to elevated baseline thyroid stimulating hormone (TSH). Baseline characteristics in the mITT were well balanced between groups, with reliable developmental assessment outcomes. Adjusted mean change in GDQ in the mITT showed similar decreases in all groups (placebo: -5.10 [95% confidence interval (CI) -7.84 to -2.37]; FA: -4.69 [95% CI -7.73 to -1.64]; L-thyroxine: -3.89 [95% CI -6.94 to -0.83]; FA+L-thyroxine: -3.86 [95% CI -6.67 to -1.06]), with no significant difference for any active treatment group versus placebo. CONCLUSION: This trial does not support the hypotheses that thyroxine and/or folinic acid improve development of young children with DS or are synergistic. This trial is registered with ClinicalTrials.gov number, NCT01576705.

Widening of the genetic and clinical spectrum of Lamb-Shaffer syndrome, a neurodevelopmental disorder due to SOX5 haploinsufficiency.

PURPOSE: Lamb-Shaffer syndrome (LAMSHF) is a neurodevelopmental disorder described in just over two dozen patients with heterozygous genetic alterations involving SOX5, a gene encoding a transcription factor regulating cell fate and differentiation in neurogenesis and other discrete developmental processes. The genetic alterations described so far are mainly microdeletions. The present study was aimed at increasing our understanding of LAMSHF, its clinical and genetic spectrum, and the pathophysiological mechanisms involved. METHODS: Clinical and genetic data were collected through GeneMatcher and clinical or genetic networks for 41 novel patients harboring various types ofSOX5 alterations. Functional consequences of selected substitutions were investigated. RESULTS: Microdeletions and truncating variants occurred throughout SOX5. In contrast, most missense variants clustered in the pivotal SOX-specific high-mobility-group domain. The latter variants prevented SOX5 from binding DNA and promoting transactivation in vitro, whereas missense variants located outside the high-mobility-group domain did not. Clinical manifestations and severity varied among patients. No clear genotype-phenotype correlations were found, except that missense variants outside the high-mobility-group domain were generally better tolerated. CONCLUSIONS: This study extends the clinical and genetic spectrum associated with LAMSHF and consolidates evidence that SOX5 haploinsufficiency leads to variable degrees of intellectual disability, language delay, and other clinical features.

Genetic variants in components of the NALCN-UNC80-UNC79 ion channel complex cause a broad clinical phenotype (NALCN channelopathies).

NALCN is a conserved cation channel, which conducts a permanent sodium leak current and regulates resting membrane potential and neuronal excitability. It is part of a large ion channel complex, the "NALCN channelosome", consisting of multiple proteins including UNC80 and UNC79. The predominant neuronal expression pattern and its function suggest an important role in neuronal function and disease. So far, biallelic NALCN and UNC80 variants have been described in a small number of individuals leading to infantile hypotonia, psychomotor retardation, and characteristic facies 1 (IHPRF1, OMIM 615419) and 2 (IHPRF2, OMIM 616801), respectively. Heterozygous de novo NALCN missense variants in the S5/S6 pore-forming segments lead to congenital contractures of the limbs and face, hypotonia, and developmental delay (CLIFAHDD, OMIM 616266) with some clinical overlap. In this study, we present detailed clinical information of 16 novel individuals with biallelic NALCN variants, 1 individual with a heterozygous de novo NALCN missense variant and an interesting clinical phenotype without contractures, and 12 individuals with biallelic UNC80 variants. We report for the first time a missense NALCN variant located in the predicted S6 pore-forming unit inherited in an autosomal-recessive manner leading to mild IHPRF1. We show evidence of clinical variability, especially among IHPRF1-affected individuals, and discuss differences between the IHPRF1- and IHPRF2 phenotypes. In summary, we provide a comprehensive overview of IHPRF1 and IHPRF2 phenotypes based on the largest cohort of individuals reported so far and provide additional insights into the clinical phenotypes of these neurodevelopmental diseases to help improve counseling of affected families.

Copy Number Variations Found in Patients with a Corpus Callosum Abnormality and Intellectual Disability.

OBJECTIVE: To evaluate the role that chromosomal micro-rearrangements play in patients with both corpus callosum abnormality and intellectual disability, we analyzed copy number variations (CNVs) in patients with corpus callosum abnormality/intellectual disability STUDY DESIGN: We screened 149 patients with corpus callosum abnormality/intellectual disability using Illumina SNP arrays. RESULTS: In 20 patients (13%), we have identified at least 1 CNV that likely contributes to corpus callosum abnormality/intellectual disability phenotype. We confirmed that the most common rearrangement in corpus callosum abnormality/intellectual disability is inverted duplication with terminal deletion of the 8p chromosome (3.2%). In addition to the identification of known recurrent CNVs, such as deletions 6qter, 18q21 (including TCF4), 1q43q44, 17p13.3, 14q12, 3q13, 3p26, and 3q26 (including SOX2), our analysis allowed us to refine the 2 known critical regions associated with 8q21.1 deletion and 19p13.1 duplication relevant for corpus callosum abnormality; report a novel 10p12 deletion including ZEB1 recently implicated in corpus callosum abnormality with corneal dystrophy; and) report a novel pathogenic 7q36 duplication encompassing SHH. In addition, 66 variants of unknown significance were identified in 57 patients encompassed candidate genes. CONCLUSIONS: Our results confirm the relevance of using microarray analysis as first line test in patients with corpus callosum abnormality/intellectual disability.

Anthropometric charts and congenital anomalies in newborns with Down syndrome.

The objectives of this study were to obtain updated neonatal measurements in French newborns with Down Syndrome (DS) according to their gestational age, and to assess the frequency and distribution of congenital anomalies. Data on congenital malformations, birth weight, birth length and birth occipito-frontal circumference (OFC) according to the gestational age was gathered from 1,030 babies, born between 1980 and 2010. The mean gestational age was 38 weeks from the date of the last menstrual period (LMP) (range: 29-42 weeks). Repartition of complications was found to be similar to previous studies, with no difference according to the date of birth. For girls born after 37 weeks, the mean birth weight was 3,012 ± 430 g, the mean birth length was 47.7 ± 2 cm, and the mean birth OFC was 33 ± 1.4 cm. For boys born after 37 weeks, the mean birth weight was 3,103 ± 459, the mean birth length was 48.4 ± 2.2 cm, and the mean birth OFC was 33.2 ± 1.4 cm. We did not find any difference in these measurements when we compared children born before 1997 and after 2007. When compared to the general population (French data and WHO charts), newborns with DS have a more pronounced difference in their birth length and their birth OFC (15-25th) than in their birth weight (25-50th). The shape of the growth curves shows that growth velocity decreases during the last weeks of gestation in all measurements, which suggests that the modal age for delivery could be earlier in DS newborns than in the general population.

Genetic and neurodevelopmental spectrum of SYNGAP1-associated intellectual disability and epilepsy.

OBJECTIVE: We aimed to delineate the neurodevelopmental spectrum associated with SYNGAP1 mutations and to investigate genotype-phenotype correlations. METHODS: We sequenced the exome or screened the exons of SYNGAP1 in a total of 251 patients with neurodevelopmental disorders. Molecular and clinical data from patients with SYNGAP1 mutations from other centres were also collected, focusing on developmental aspects and the associated epilepsy phenotype. A review of SYNGAP1 mutations published in the literature was also performed. RESULTS: We describe 17 unrelated affected individuals carrying 13 different novel loss-of-function SYNGAP1 mutations. Developmental delay was the first manifestation of SYNGAP1-related encephalopathy; intellectual disability became progressively obvious and was associated with autistic behaviours in eight patients. Hypotonia and unstable gait were frequent associated neurological features. With the exception of one patient who experienced a single seizure, all patients had epilepsy, characterised by falls or head drops due to atonic or myoclonic seizures, (myoclonic) absences and/or eyelid myoclonia. Triggers of seizures were frequent (n=7). Seizures were pharmacoresistant in half of the patients. The severity of the epilepsy did not correlate with the presence of autistic features or with the severity of cognitive impairment. Mutations were distributed throughout the gene, but spared spliced 3' and 5' exons. Seizures in patients with mutations in exons 4-5 were more pharmacoresponsive than in patients with mutations in exons 8-15. CONCLUSIONS: SYNGAP1 encephalopathy is characterised by early neurodevelopmental delay typically preceding the onset of a relatively recognisable epilepsy comprising generalised seizures (absences, myoclonic jerks) and frequent triggers.

Nail and phalangeal agenesis in a patient with 4pter and 9pter duplication.

We report on an 8-month-old girl with intra-uterine growth retardation, microcephaly, incomplete cleft lip, axial hypotonia, failure to thrive, and brachydactyly type B (phalangeal agenesis and absence of nails). She carried a supernumerary marker chromosome derived from chromosomes 4 and 9, leading to 4pter-q12 and 9pter-p21.2 duplication. The marker was derived from the 3:1 segregation of a maternal balanced translocation 46,XX, t(4;9)(q12;p21.2). The proposita is the first reported individual with distal phalangeal agenesis and anonychia, and trisomy 4p and partial trisomy 9p due to 3:1 segregation of a maternal reciprocal translocation.

Hyperechoic Content of the Fetal Colon Is Not Always Cystinuria-Case Report.

Cystinuria is a recessively inherited genetic disease causing recurrent kidney stones with risk of kidney failure. The discovery of hyperechoic colonic content on an antenatal ultrasound is considered to be a pathognomic sign of cystinuria. Herein, we present a clinical case with antenatal diagnosis of cystinuria in an ultrasound finding, which eventually revealed a multisystem disease, characterized by the association of renal Fanconi syndrome, hyperinsulinemic hypoglycemia, and hepatic dysfunction. Genetic investigations evidenced the recurrent heterozygous missense HNF4A (p.Arg76Trp) variant. Our case report shows that antenatal hyperechoic colonic content can hide a complex proximal renal tubulopathy, and questions the genetic counseling provided to families in the antenatal period.

Elp2 mutations perturb the epitranscriptome and lead to a complex neurodevelopmental phenotype.

Intellectual disability (ID) and autism spectrum disorder (ASD) are the most common neurodevelopmental disorders and are characterized by substantial impairment in intellectual and adaptive functioning, with their genetic and molecular basis remaining largely unknown. Here, we identify biallelic variants in the gene encoding one of the Elongator complex subunits, ELP2, in patients with ID and ASD. Modelling the variants in mice recapitulates the patient features, with brain imaging and tractography analysis revealing microcephaly, loss of white matter tract integrity and an aberrant functional connectome. We show that the Elp2 mutations negatively impact the activity of the complex and its function in translation via tRNA modification. Further, we elucidate that the mutations perturb protein homeostasis leading to impaired neurogenesis, myelin loss and neurodegeneration. Collectively, our data demonstrate an unexpected role for tRNA modification in the pathogenesis of monogenic ID and ASD and define Elp2 as a key regulator of brain development.

Clinical impact of post-mortem genetic testing in cardiac death and cardiomyopathy.

Post-mortem genetic analyses may help to elucidate the cause of cardiac death. The added value is however unclear when a cardiac disease is already suspected or affirmed. Our aim was to study the feasibility and medical impact of post-mortem genetic analyses in suspected cardiomyopathy. We studied 35 patients with cardiac death and suspected cardiomyopathy based on autopsy or clinical data. After targeted sequencing, we identified 15 causal variants in 15 patients (yield 43%) in sarcomeric (n = 8), desmosomal (n = 3), lamin A/C (n = 3) and transthyretin (n = 1) genes. The results had various impacts on families, i.e. allowed predictive genetic testing in relatives (15 families), planned early therapeutics based on the specific underlying gene (5 families), rectified the suspected cardiomyopathy subtype (2 families), assessed the genetic origin of cardiomyopathy that usually has an acquired cause (1 family), assessed the diagnosis in a patient with uncertain borderline cardiomyopathy (1 family), reassured the siblings because of a de novo mutation (2 families) and allowed prenatal testing (1 family). Our findings suggest that post-mortem molecular testing should be included in the strategy of family care after cardiac death and suspected cardiomyopathy, since genetic findings provide additional information useful for relatives, which are beyond conventional autopsy.

Erratum: Author Correction: A framework to identify contributing genes in patients with Phelan-McDermid syndrome.

[This corrects the article DOI: 10.1038/s41525-017-0035-2.].

Acute Regression in Young People with Down Syndrome.

Abstract: Adolescents and young adults with Down syndrome (DS) can present a rapid regression with loss of independence and daily skills. Causes of regression are unknown and treatment is most of the time symptomatic. We did a retrospective cohort study of regression cases: patients were born between 1959 and 2000, and were followed from 1984 to now. We found 30 DS patients aged 11 to 30 years old with history of regression. Regression occurred regardless of the cognitive level (severe, moderate, or mild intellectual disability (ID)). Patients presented psychiatric symptoms (catatonia, depression, delusions, stereotypies, etc.), partial or total loss of independence in activities of daily living (dressing, toilet, meals, and continence), language impairment (silence, whispered voice, etc.), and loss of academic skills. All patients experienced severe emotional stress prior to regression, which may be considered the trigger. Partial or total recovery was observed for about 50% of them. In our cohort, girls were more frequently affected than boys (64%). Neurobiological hypotheses are discussed as well as preventative and therapeutic approaches.

A framework to identify contributing genes in patients with Phelan-McDermid syndrome.

Phelan-McDermid syndrome (PMS) is characterized by a variety of clinical symptoms with heterogeneous degrees of severity, including intellectual disability (ID), absent or delayed speech, and autism spectrum disorders (ASD). It results from a deletion of the distal part of chromosome 22q13 that in most cases includes the SHANK3 gene. SHANK3 is considered a major gene for PMS, but the factors that modulate the severity of the syndrome remain largely unknown. In this study, we investigated 85 patients with different 22q13 rearrangements (78 deletions and 7 duplications). We first explored the clinical features associated with PMS, and provide evidence for frequent corpus callosum abnormalities in 28% of 35 patients with brain imaging data. We then mapped several candidate genomic regions at the 22q13 region associated with high risk of clinical features, and suggest a second locus at 22q13 associated with absence of speech. Finally, in some cases, we identified additional clinically relevant copy-number variants (CNVs) at loci associated with ASD, such as 16p11.2 and 15q11q13, which could modulate the severity of the syndrome. We also report an inherited SHANK3 deletion transmitted to five affected daughters by a mother without ID nor ASD, suggesting that some individuals could compensate for such mutations. In summary, we shed light on the genotype-phenotype relationship of patients with PMS, a step towards the identification of compensatory mechanisms for a better prognosis and possibly treatments of patients with neurodevelopmental disorders.