Expanding the genetic and clinical spectrum of Tatton-Brown-Rahman syndrome in a series of 24 French patients.

BACKGROUND: Tatton-Brown-Rahman syndrome (TBRS; OMIM 615879), also known as DNA methyltransferase 3 alpha (DNMT3A)-overgrowth syndrome (DOS), was first described by Tatton-Brown in 2014. This syndrome is characterised by overgrowth, intellectual disability and distinctive facial features and is the consequence of germline loss-of-function variants in DNMT3A, which encodes a DNA methyltransferase involved in epigenetic regulation. Somatic variants of DNMT3A are frequently observed in haematological malignancies, including acute myeloid leukaemia (AML). To date, 100 individuals with TBRS with de novo germline variants have been described. We aimed to further characterise this disorder clinically and at the molecular level in a nationwide series of 24 French patients and to investigate the correlation between the severity of intellectual disability and the type of variant. METHODS: We collected genetic and medical information from 24 individuals with TBRS using a questionnaire released through the French National AnDDI-Rares Network. RESULTS: Here, we describe the first nationwide French cohort of 24 individuals with germline likely pathogenic/pathogenic variants in DNMT3A, including 17 novel variants. We confirmed that the main phenotypic features were intellectual disability (100% of individuals), distinctive facial features (96%) and overgrowth (87%). We highlighted novel clinical features, such as hypertrichosis, and further described the neurological features and EEG results. CONCLUSION: This study of a nationwide cohort of individuals with TBRS confirms previously published data and provides additional information and clarifies clinical features to facilitate diagnosis and improve care. This study adds value to the growing body of knowledge on TBRS and broadens its clinical and molecular spectrum.

Cerebral dural arteriovenous fistulas in patients with PTEN-related hamartoma tumor syndrome.

Central nervous system (CNS) dural arteriovenous fistulas (DAVF) have been reported in PTEN-related hamartoma tumor syndrome (PHTS). However, PHTS-associated DAVF remain an underexplored field of the PHTS clinical landscape. Here, we studied cases with a PTEN pathogenic variant identified between 2007 and 2020 in our laboratory (n = 58), and for whom brain imaging was available. Two patients had DAVF (2/58, 3.4%), both presenting at advanced stages: a 34-year-old man with a left lateral sinus DAVF at immediate risk of hemorrhage, and a 21-year-old woman with acute intracranial hypertension due to a torcular DAVF. Interestingly, not all patients had 3D TOF/MRA, the optimal sequences to detect DAVF. Early diagnosis of DAVF can be lifesaving, and is easier to treat compared to developed, proliferative, or complex lesions. As a result, one should consider brain MRI with 3D TOF/MRA in PHTS patients at genetic diagnosis, with subsequent surveillance on a case-by-case basis.

Recessive NUP54 Variants Underlie Early-Onset Dystonia with Striatal Lesions.

Infantile striatonigral degeneration is caused by a homozygous variant of the nuclear-pore complex (NPC) gene NUP62, involved in nucleo-cytoplasmic trafficking. By querying sequencing-datasets of patients with dystonia and/or Leigh(-like) syndromes, we identified 3 unrelated individuals with biallelic variants in NUP54. All variants clustered in the C-terminal protein region that interacts with NUP62. Associated phenotypes were similar to those of NUP62-related disease, including early-onset dystonia with dysphagia, choreoathetosis, and T2-hyperintense lesions in striatum. In silico and protein-biochemical studies gave further evidence for the argument that the variants were pathogenic. We expand the spectrum of NPC component-associated dystonic conditions with localized basal-ganglia abnormalities. ANN NEUROL 2023;93:330-335.

Early-Onset Osteoporosis: Molecular Analysis in Large Cohort and Focus on the PLS3 Gene.

Osteoporosis is a skeletal disorder characterized by abnormal bone microarchitecture and low bone mineral density (BMD), responsible for an increased risk of fractures and skeletal fragility. It is a common pathology of the aging population. However, when osteoporosis occurs in children or young adults, it strongly suggests an underlying genetic etiology. Over the past two decades, several genes have been identified as responsible for this particular kind of considered monogenic early-onset osteoporosis (EOOP) or juvenile osteoporosis, the main ones being COL1A1, COL1A2, LRP5, LRP6, WNT1, and more recently PLS3. In this study, the objective was to characterize a large cohort of patients diagnosed with primary osteoporosis and to establish its diagnosis yield. The study included 577 patients diagnosed with primary osteoporosis and its diagnosis yield was established. To this end, next-generation sequencing (NGS) of a panel of 21 genes known to play a role in bone fragility was carried out. A genetic etiology was explained in about 18% of cases, while the others remain unexplained. The most frequently identified gene associated with EOOP is LRP5, which was responsible for 8.2% of the positive results (47 patients). As unexpected, 17 patients (2.9%) had a variant in PLS3 which encodes plastin 3. Alterations of PLS3 are associated with dominant X-linked osteoporosis, an extremely rare disease. Given the rarity of this disease, we focused on it. It was observed that males were more affected than females, but it is noteworthy that three females with a particularly severe phenotype were identified. Of these three, two had a variant in an additional gene involved in EOP, illustrating the probable existence of digenism. We significantly increase the number of variants potentially associated with EOOP, especially in PLS3. The results of our study demonstrate that molecular analysis in EOOP is beneficial and useful.

Cat eye syndrome: Clinical, cytogenetics and familial findings in a large cohort of 43 patients highlighting the importance of congenital heart disease and inherited cases.

Cat Eye Syndrome (CES) is a rare genetic disease caused by the presence of a small supernumerary marker chromosome derived from chromosome 22, which results in a partial tetrasomy of 22p-22q11.21. CES is classically defined by association of iris coloboma, anal atresia, and preauricular tags or pits, with high clinical and genetic heterogeneity. We conducted an international retrospective study of patients carrying genomic gain in the 22q11.21 chromosomal region upstream from LCR22-A identified using FISH, MLPA, and/or array-CGH. We report a cohort of 43 CES cases. We highlight that the clinical triad represents no more than 50% of cases. However, only 16% of CES patients presented with the three signs of the triad and 9% not present any of these three signs. We also highlight the importance of other impairments: cardiac anomalies are one of the major signs of CES (51% of cases), and high frequency of intellectual disability (47%). Ocular motility defects (45%), abdominal malformations (44%), ophthalmologic malformations (35%), and genitourinary tract defects (32%) are other frequent clinical features. We observed that sSMC is the most frequent chromosomal anomaly (91%) and we highlight the high prevalence of mosaic cases (40%) and the unexpectedly high prevalence of parental transmission of sSMC (23%). Most often, the transmitting parent has mild or absent features and carries the mosaic marker at a very low rate (<10%). These data allow us to better delineate the clinical phenotype associated with CES, which must be taken into account in the cytogenetic testing for this syndrome. These findings draw attention to the need for genetic counseling and the risk of recurrence.

Putative founder effect of Arg338* AP4M1 (SPG50) variant causing severe intellectual disability, epilepsy and spastic paraplegia: Report of three families.

Bi-allelic variants affecting one of the four genes encoding the AP4 subunits are responsible for the "AP4 deficiency syndrome." Core features include hypotonia that progresses to hypertonia and spastic paraplegia, intellectual disability, postnatal microcephaly, epilepsy, and neuroimaging features. Namely, AP4M1 (SPG50) is involved in autosomal recessive spastic paraplegia 50 (MIM#612936). We report on three patients with core features from three unrelated consanguineous families originating from the Middle East. Exome sequencing identified the same homozygous nonsense variant: NM_004722.4(AP4M1):c.1012C>T p.Arg338* (rs146262009). So far, four patients from three other families carrying this homozygous variant have been reported worldwide. We describe their phenotype and compare it to the phenotype of patients with other variants in AP4M1. We construct a shared single-nucleotide polymorphism (SNP) haplotype around AP4M1 in four families and suggest a probable founder effect of Arg338* AP4M1 variant with a common ancestor most likely of Turkish origin.

Deep intronic NIPBL de novo mutations and differential diagnoses revealed by whole genome and RNA sequencing in Cornelia de Lange syndrome patients.

Cornelia de Lange syndrome (CdLS; MIM# 122470) is a rare developmental disorder. Pathogenic variants in 5 genes explain approximately 50% cases, leaving the other 50% unsolved. We performed whole genome sequencing (WGS) ± RNA sequencing (RNA-seq) in 5 unsolved trios fulfilling the following criteria: (i) clinical diagnosis of classic CdLS, (ii) negative gene panel sequencing from blood and saliva-isolated DNA, (iii) unaffected parents' DNA samples available and (iv) proband's blood-isolated RNA available. A pathogenic de novo mutation (DNM) was observed in a CdLS differential diagnosis gene in 3/5 patients, namely POU3F3, SPEN, and TAF1. In the other two, we identified two distinct deep intronic DNM in NIPBL predicted to create a novel splice site. RT-PCRs and RNA-Seq showed aberrant transcripts leading to the creation of a novel frameshift exon. Our findings suggest the relevance of WGS in unsolved suspected CdLS cases and that deep intronic variants may account for a proportion of them.

Targeted next-generation sequencing in a large series of fetuses with severe renal diseases.

We report the screening of a large panel of genes in a series of 100 fetuses (98 families) affected with severe renal defects. Causative variants were identified in 22% of cases, greatly improving genetic counseling. The percentage of variants explaining the phenotype was different according to the type of phenotype. The highest diagnostic yield was found in cases affected with the ciliopathy-like phenotype (11/15 families and, in addition, a single heterozygous or a homozygous Class 3 variant in PKHD1 in three unrelated cases with autosomal recessive polycystic kidney disease). The lowest diagnostic yield was observed in cases with congenital anomalies of the kidney and urinary tract (9/78 families and, in addition, Class 3 variants in GREB1L in three unrelated cases with bilateral renal agenesis). Inheritance was autosomal recessive in nine genes (PKHD1, NPHP3, CEP290, TMEM67, DNAJB11, FRAS1, ACE, AGT, and AGTR1), and autosomal dominant in six genes (PKD1, PKD2, PAX2, EYA1, BICC1, and MYOCD). Finally, we developed an original approach of next-generation sequencing targeted RNA sequencing using the custom capture panel used for the sequencing of DNA, to validate one MYOCD heterozygous splicing variant identified in two male siblings with megabladder and inherited from their healthy mother.

MYT1L-associated neurodevelopmental disorder: description of 40 new cases and literature review of clinical and molecular aspects.

Pathogenic variants of the myelin transcription factor-1 like (MYT1L) gene include heterozygous missense, truncating variants and 2p25.3 microdeletions and cause a syndromic neurodevelopmental disorder (OMIM#616,521). Despite enrichment in de novo mutations in several developmental disorders and autism studies, the data on clinical characteristics and genotype-phenotype correlations are scarce, with only 22 patients with single nucleotide pathogenic variants reported. We aimed to further characterize this disorder at both the clinical and molecular levels by gathering a large series of patients with MYT1L-associated neurodevelopmental disorder. We collected genetic information on 40 unreported patients with likely pathogenic/pathogenic MYT1L variants and performed a comprehensive review of published data (total = 62 patients). We confirm that the main phenotypic features of the MYT1L-related disorder are developmental delay with language delay (95%), intellectual disability (ID, 70%), overweight or obesity (58%), behavioral disorders (98%) and epilepsy (23%). We highlight novel clinical characteristics, such as learning disabilities without ID (30%) and feeding difficulties during infancy (18%). We further describe the varied dysmorphic features (67%) and present the changes in weight over time of 27 patients. We show that patients harboring highly clustered missense variants in the 2-3-ZNF domains are not clinically distinguishable from patients with truncating variants. We provide an updated overview of clinical and genetic data of the MYT1L-associated neurodevelopmental disorder, hence improving diagnosis and clinical management of these patients.

Rare De Novo Missense Variants in RNA Helicase DDX6 Cause Intellectual Disability and Dysmorphic Features and Lead to P-Body Defects and RNA Dysregulation.

The human RNA helicase DDX6 is an essential component of membrane-less organelles called processing bodies (PBs). PBs are involved in mRNA metabolic processes including translational repression via coordinated storage of mRNAs. Previous studies in human cell lines have implicated altered DDX6 in molecular and cellular dysfunction, but clinical consequences and pathogenesis in humans have yet to be described. Here, we report the identification of five rare de novo missense variants in DDX6 in probands presenting with intellectual disability, developmental delay, and similar dysmorphic features including telecanthus, epicanthus, arched eyebrows, and low-set ears. All five missense variants (p.His372Arg, p.Arg373Gln, p.Cys390Arg, p.Thr391Ile, and p.Thr391Pro) are located in two conserved motifs of the RecA-2 domain of DDX6 involved in RNA binding, helicase activity, and protein-partner binding. We use functional studies to demonstrate that the first variants identified (p.Arg373Gln and p.Cys390Arg) cause significant defects in PB assembly in primary fibroblast and model human cell lines. These variants' interactions with several protein partners were also disrupted in immunoprecipitation assays. Further investigation via complementation assays included the additional variants p.Thr391Ile and p.Thr391Pro, both of which, similarly to p.Arg373Gln and p.Cys390Arg, demonstrated significant defects in P-body assembly. Complementing these molecular findings, modeling of the variants on solved protein structures showed distinct spatial clustering near known protein binding regions. Collectively, our clinical and molecular data describe a neurodevelopmental syndrome associated with pathogenic missense variants in DDX6. Additionally, we suggest DDX6 join the DExD/H-box genes DDX3X and DHX30 in an emerging class of neurodevelopmental disorders involving RNA helicases.

Heterozygous variants in CTR9, which encodes a major component of the PAF1 complex, are associated with a neurodevelopmental disorder.

PURPOSE: CTR9 is a subunit of the PAF1 complex (PAF1C) that plays a crucial role in transcription regulation by binding CTR9 to RNA polymerase II. It is involved in transcription-coupled histone modification through promoting H3K4 and H3K36 methylation. We describe the clinical and molecular studies in 13 probands, harboring likely pathogenic CTR9 missense variants, collected through GeneMatcher. METHODS: Exome sequencing was performed in all individuals. CTR9 variants were assessed through 3-dimensional modeling of the activated human transcription complex Pol II-DSIF-PAF-SPT6 and the PAF1/CTR9 complex. H3K4/H3K36 methylation analysis, mitophagy assessment based on tetramethylrhodamine ethyl ester perchlorate immunofluorescence, and RNA-sequencing in skin fibroblasts from 4 patients was performed. RESULTS: Common clinical findings were variable degrees of intellectual disability, hypotonia, joint hyperlaxity, speech delay, coordination problems, tremor, and autism spectrum disorder. Mild dysmorphism and cardiac anomalies were less frequent. For 11 CTR9 variants, de novo occurrence was shown. Three-dimensional modeling predicted a likely disruptive effect of the variants on local CTR9 structure and protein interaction. Additional studies in fibroblasts did not unveil the downstream functional consequences of the identified variants. CONCLUSION: We describe a neurodevelopmental disorder caused by (mainly) de novo variants in CTR9, likely affecting PAF1C function.

Structural mapping of GABRB3 variants reveals genotype-phenotype correlations.

PURPOSE: Pathogenic variants in GABRB3 have been associated with a spectrum of phenotypes from severe developmental disorders and epileptic encephalopathies to milder epilepsy syndromes and mild intellectual disability (ID). In this study, we analyzed a large cohort of individuals with GABRB3 variants to deepen the phenotypic understanding and investigate genotype-phenotype correlations. METHODS: Through an international collaboration, we analyzed electro-clinical data of unpublished individuals with variants in GABRB3, and we reviewed previously published cases. All missense variants were mapped onto the 3-dimensional structure of the GABRB3 subunit, and clinical phenotypes associated with the different key structural domains were investigated. RESULTS: We characterized 71 individuals with GABRB3 variants, including 22 novel subjects, expressing a wide spectrum of phenotypes. Interestingly, phenotypes correlated with structural locations of the variants. Generalized epilepsy, with a median age at onset of 12 months, and mild-to-moderate ID were associated with variants in the extracellular domain. Focal epilepsy with earlier onset (median: age 4 months) and severe ID were associated with variants in both the pore-lining helical transmembrane domain and the extracellular domain. CONCLUSION: These genotype-phenotype correlations will aid the genetic counseling and treatment of individuals affected by GABRB3-related disorders. Future studies may reveal whether functional differences underlie the phenotypic differences.

Neurocognitive and neurobehavioral characterization of two frequent forms of neurodevelopmental disorders: the DYRK1A and the Wiedemann-Steiner syndromes.

DYRK1A and Wiedemann-Steiner syndromes (WSS) are two genetic conditions associated with neurodevelopmental disorders (NDDs). Although their clinical phenotype has been described, their behavioral phenotype has not systematically been studied using standardized assessment tools. To characterize the latter, we conducted a retrospective study, collecting data on developmental history, autism spectrum disorder (ASD), adaptive functioning, behavioral assessments, and sensory processing of individuals with these syndromes (n = 14;21). In addition, we analyzed information collected from families (n = 20;20) using the GenIDA database, an international patient-driven data collection aiming to better characterize natural history of genetic forms of NDDs. In the retrospective study, individuals with DYRK1A syndrome showed lower adaptive behavior scores compared to those with WSS, whose scores showed greater heterogeneity. An ASD diagnosis was established for 57% (8/14) of individuals with DYRK1A syndrome and 24% (5/21) of those with WSS. Language and communication were severely impaired in individuals with DYRK1A syndrome, which was also evident from GenIDA data, whereas in WSS patients, exploration of behavioral phenotypes revealed the importance of anxiety symptomatology and ADHD signs, also flagged in GenIDA. This study, describing the behavioral and sensorial profiles of individuals with WSS and DYRK1A syndrome, highlighted some specificities important to be considered for patients' management.

Molecular and clinical descriptions of patients with GABAA receptor gene variants (GABRA1, GABRB2, GABRB3, GABRG2): A cohort study, review of literature, and genotype-phenotype correlation.

OBJECTIVE: γ-Aminobutyric acid (GABA)A -receptor subunit variants have recently been associated with neurodevelopmental disorders and/or epilepsy. The phenotype linked with each gene is becoming better known. Because of the common molecular structure and physiological role of these phenotypes, it seemed interesting to describe a putative phenotype associated with GABAA -receptor-related disorders as a whole and seek possible genotype-phenotype correlations. METHODS: We collected clinical, electrophysiological, therapeutic, and molecular data from patients with GABAA -receptor subunit variants (GABRA1, GABRB2, GABRB3, and GABRG2) through a national French collaboration using the EPIGENE network and compared these data to the one already described in the literature. RESULTS: We gathered the reported patients in three epileptic phenotypes: 15 patients with fever-related epilepsy (40%), 11 with early developmental epileptic encephalopathy (30%), 10 with generalized epilepsy spectrum (27%), and 1 patient without seizures (3%). We did not find a specific phenotype for any gene, but we showed that the location of variants on the transmembrane (TM) segment was associated with a more severe phenotype, irrespective of the GABAA -receptor subunit gene, whereas N-terminal variants seemed to be related to milder phenotypes. SIGNIFICANCE: GABAA -receptor subunit variants are associated with highly variable phenotypes despite their molecular and physiological proximity. None of the genes described here was associated with a specific phenotype. On the other hand, it appears that the location of the variant on the protein may be a marker of severity. Variant location may have important weight in the development of targeted therapeutics.

Genotype-first in a cohort of 95 fetuses with multiple congenital abnormalities: when exome sequencing reveals unexpected fetal phenotype-genotype correlations.

PURPOSE: Molecular diagnosis based on singleton exome sequencing (sES) is particularly challenging in fetuses with multiple congenital abnormalities (MCA). Indeed, some studies reveal a diagnostic yield of about 20%, far lower than in live birth individuals showing developmental abnormalities (30%), suggesting that standard analyses, based on the correlation between clinical hallmarks described in postnatal syndromic presentations and genotype, may underestimate the impact of the genetic variants identified in fetal analyses. METHODS: We performed sES in 95 fetuses with MCA. Blind to phenotype, we applied a genotype-first approach consisting of combined analyses based on variants annotation and bioinformatics predictions followed by reverse phenotyping. Initially applied to OMIM-morbid genes, analyses were then extended to all genes. We complemented our approach by using reverse phenotyping, variant segregation analysis, bibliographic search and data sharing in order to establish the clinical significance of the prioritised variants. RESULTS: sES rapidly identified causal variant in 24/95 fetuses (25%), variants of unknown significance in OMIM genes in 8/95 fetuses (8%) and six novel candidate genes in 6/95 fetuses (6%). CONCLUSIONS: This method, based on a genotype-first approach followed by reverse phenotyping, shed light on unexpected fetal phenotype-genotype correlations, emphasising the relevance of prenatal studies to reveal extreme clinical presentations associated with well-known Mendelian disorders.

Clinical Utility of a Unique Genome-Wide DNA Methylation Signature for KMT2A-Related Syndrome.

Wiedemann-Steiner syndrome (WDSTS) is a Mendelian syndromic intellectual disability (ID) condition associated with hypertrichosis cubiti, short stature, and characteristic facies caused by pathogenic variants in the KMT2A gene. Clinical features can be inconclusive in mild and unusual WDSTS presentations with variable ID (mild to severe), facies (typical or not) and other associated malformations (bone, cerebral, renal, cardiac and ophthalmological anomalies). Interpretation and classification of rare KMT2A variants can be challenging. A genome-wide DNA methylation episignature for KMT2A-related syndrome could allow functional classification of variants and provide insights into the pathophysiology of WDSTS. Therefore, we assessed genome-wide DNA methylation profiles in a cohort of 60 patients with clinical diagnosis for WDSTS or Kabuki and identified a unique highly sensitive and specific DNA methylation episignature as a molecular biomarker of WDSTS. WDSTS episignature enabled classification of variants of uncertain significance in the KMT2A gene as well as confirmation of diagnosis in patients with clinical presentation of WDSTS without known genetic variants. The changes in the methylation profile resulting from KMT2A mutations involve global reduction in methylation in various genes, including homeobox gene promoters. These findings provide novel insights into the molecular etiology of WDSTS and explain the broad phenotypic spectrum of the disease.

Episignature Mapping of TRIP12 Provides Functional Insight into Clark-Baraitser Syndrome.

Clark-Baraitser syndrome is a rare autosomal dominant intellectual disability syndrome caused by pathogenic variants in the TRIP12 (Thyroid Hormone Receptor Interactor 12) gene. TRIP12 encodes an E3 ligase in the ubiquitin pathway. The ubiquitin pathway includes activating E1, conjugating E2 and ligating E3 enzymes which regulate the breakdown and sorting of proteins. This enzymatic pathway is crucial for physiological processes. A significant proportion of TRIP12 variants are currently classified as variants of unknown significance (VUS). Episignatures have been shown to represent a powerful diagnostic tool to resolve inconclusive genetic findings for Mendelian disorders and to re-classify VUSs. Here, we show the results of DNA methylation episignature analysis in 32 individuals with pathogenic, likely pathogenic and VUS variants in TRIP12. We identified a specific and sensitive DNA methylation (DNAm) episignature associated with pathogenic TRIP12 variants, establishing its utility as a clinical biomarker for Clark-Baraitser syndrome. In addition, we performed analysis of differentially methylated regions as well as functional correlation of the TRIP12 genome-wide methylation profile with the profiles of 56 additional neurodevelopmental disorders.

Integrative approach to interpret DYRK1A variants, leading to a frequent neurodevelopmental disorder.

PURPOSE: DYRK1A syndrome is among the most frequent monogenic forms of intellectual disability (ID). We refined the molecular and clinical description of this disorder and developed tools to improve interpretation of missense variants, which remains a major challenge in human genetics. METHODS: We reported clinical and molecular data for 50 individuals with ID harboring DYRK1A variants and developed (1) a specific DYRK1A clinical score; (2) amino acid conservation data generated from 100 DYRK1A sequences across different taxa; (3) in vitro overexpression assays to study level, cellular localization, and kinase activity of DYRK1A mutant proteins; and (4) a specific blood DNA methylation signature. RESULTS: This integrative approach was successful to reclassify several variants as pathogenic. However, we questioned the involvement of some others, such as p.Thr588Asn, still reported as likely pathogenic, and showed it does not cause an obvious phenotype in mice. CONCLUSION: Our study demonstrated the need for caution when interpreting variants in DYRK1A, even those occurring de novo. The tools developed will be useful to interpret accurately the variants identified in the future in this gene.

Skraban-Deardorff syndrome: Six new cases of WDR26-related disease and expansion of the clinical phenotype.

Skraban-Deardorff syndrome (a disease related to variations in the WDR26 gene; OMIM #617616) was first described in a cohort of 15 individuals in 2017. The syndrome comprises intellectual deficiency, severe speech impairment, ataxic gait, seizures, mild hypotonia with feeding difficulties during infancy, and dysmorphic features. Here, we report on six novel heterozygous de novo pathogenic variants in WDR26 in six probands. The patients' phenotypes were consistent with original publication. One patient displayed marked hypotonia with an abnormal muscle biopsy; this finding warrants further investigation. Gait must be closely monitored, in order to highlight any musculoskeletal or neurological abnormalities and prompt further examinations. Speech therapy and alternative communication methods should be initiated early in the clinical follow-up, in order to improve language and oral eating and drinking.

Periodontal (formerly type VIII) Ehlers-Danlos syndrome: Description of 13 novel cases and expansion of the clinical phenotype.

Periodontal Ehlers-Danlos syndrome (pEDS) is a rare condition caused by pathogenic variants in the C1R and C1S genes, encoding subunits C1r and C1s of the first component of the classical complement pathway. It is characterized by early-onset periodontitis with premature tooth loss, pretibial hyperpigmentation and skin fragility. Rare arterial complications have been reported, but venous insufficiency is rarely described. Here we report 13 novel patients carrying heterozygous pathogenic variants in C1R and C1S including three novel C1S variants (c.962G > C, c.961 T > G and c.961 T > A). In addition to the pEDS phenotype, three patients and one relative displayed widespread venous insufficiency leading to persistent varicose leg ulcers. One patient suffered an intracranial aneurysm with familial vascular complications including thoracic and abdominal aortic aneurysm and dissection and intracranial aneurysm rupture. This work confirms that vascular complications can occur, although they are not frequent, which leads us to propose to carry out a first complete non-invasive vascular evaluation at the time of the diagnosis in pEDS patients. However, larger case series are needed to improve our understanding of the link between complement pathway activation and connective tissue alterations observed in these patients, and to better assess the frequency, type and consequences of the vascular complications.