Classical-like Ehlers-Danlos syndrome: a clinical description of 20 newly identified individuals with evidence of tissue fragility

Ehlers-Danlos syndromes: importance of defining the type

Ehlers-Danlos syndromes (EDS) is an umbrella term describing 14 types, of which 13 are rare and monogenic, with overlapping features of joint hypermobility, skin, and vascular fragility, and generalised connective tissue friability. Hypermobile EDS currently has no identified genetic cause. Most of the rare monogenic EDS types can have neurological features, which are often part of major or minor diagnostic criteria for each type. This review aims to highlight the neurological features and other key characteristics of these EDS types. This should improve recognition of these features, enabling more timely consideration and confirmation or exclusion through genetic testing. In practice, many healthcare professionals still refer to patients as having 'EDS'. However, the different EDS types have distinct clinical features as well as different underlying genetic causes and pathogenic mechanisms, and each requires bespoke management and surveillance. Defining the EDS type is therefore crucial, as EDS is not in itself a diagnosis.

Clinical and molecular delineation of classical-like Ehlers-Danlos syndrome through a comprehensive next-generation sequencing-based screening system

Classical-like Ehlers-Danlos syndrome (clEDS) is an autosomal recessive disorder caused by complete absence of tenascin-X resulting from biallelic variation in TNXB. Thus far, 50 patients from 43 families with biallelic TNXB variants have been identified. Accurate detection of TNXB variants is challenging because of the presence of the pseudogene TNXA, which can undergo non-allelic homologous recombination. Therefore, we designed a genetic screening system that is performed using similar operations to other next-generation sequencing (NGS) panel analyses and can be applied to accurately detect TNXB variants and the recombination of TNXA-derived sequences into TNXB. Using this system, we identified biallelic TNXB variants in nine unrelated clEDS patients. TNXA-derived variations were found in >75% of the current cohort, comparable to previous reports. The current cohort generally exhibited similar clinical features to patients in previous reports, but had a higher frequency of gastrointestinal complications (e.g., perforation, diverticulitis, gastrointestinal bleeding, intestinal obstruction, rectal/anal prolapse, and gallstones). This report is the first to apply an NGS-based screening for TNXB variants and represents the third largest cohort of clEDS, highlighting the importance of increasing awareness of the risk of gastrointestinal complications.

Smoking Suppresses the Therapeutic Potential of Adipose Stem Cells in Crohn’s Disease Patients through Epigenetic Changes

Patients with Crohn’s disease (CD) who smoke are known to have a worse prognosis than never-smokers and a higher risk for post-surgical recurrence, whereas patients who quit smoking after surgery have significantly lower post-operative recurrence. The hypothesis was that smoking induces epigenetic changes that impair the capacity of adipose stem cells (ASCs) to suppress the immune system. It was also questioned whether this impairment remains in ex-smokers with CD. ASCs were isolated from non-smokers, smokers and ex-smokers with CD and their interactions with immune cells were studied. The ASCs from both smokers and ex-smokers promoted macrophage polarization to an M1 pro-inflammatory phenotype, were not able to inhibit T- and B-cell proliferation in vitro and enhanced the gene and protein expression of inflammatory markers including interleukin-1b. Genome-wide epigenetic analysis using two different bioinformatic approaches revealed significant changes in the methylation patterns of genes that are critical for wound healing, immune and metabolic response and p53-mediated DNA damage response in ASCs from smokers and ex-smokers with CD. In conclusion, cigarette smoking induces a pro-inflammatory epigenetic signature in ASCs that likely compromises their therapeutic potential.

Tenascin-X as a causal gene for classical-like Ehlers-Danlos syndrome

Tenascin-X (TNX) is an extracellular matrix glycoprotein for which a deficiency results in a recessive form of classical-like Ehlers-Danlos syndrome (clEDS), a heritable connective tissue disorder with hyperextensible skin without atrophic scarring, joint hypermobility, and easy bruising. Notably, patients with clEDS also suffer from not only chronic joint pain and chronic myalgia but also neurological abnormalities such as peripheral paresthesia and axonal polyneuropathy with high frequency. By using TNX-deficient (Tnxb−/−) mice, well-known as a model animal of clEDS, we recently showed that Tnxb−/− mice exhibit hypersensitivity to chemical stimuli and the development of mechanical allodynia due to the hypersensitization of myelinated A-fibers and activation of the spinal dorsal horn. Pain also occurs in other types of EDS. First, we review the underlying molecular mechanisms of pain in EDS, especially that in clEDS. In addition, the roles of TNX as a tumor suppressor protein in cancer progression have been reported. Recent in silico large-scale database analyses have shown that TNX is downregulated in various tumor tissues and that high expression of TNX in tumor cells has a good prognosis. We describe what is so far known about TNX as a tumor suppressor protein. Furthermore, some patients with clEDS show delayed wound healing. Tnxb−/− mice also exhibit impairment of epithelial wound healing in corneas. TNX is also involved in liver fibrosis. We address the molecular mechanism for the induction of COL1A1 by the expression of both a peptide derived from the fibrinogen-related domain of TNX and integrin α11.

An exemplary model of genetic counselling for highly specialised services

With genomic testing being increasingly integrated into every day clinical practice and a wide range of practitioners ordering genetic tests, it is important that the scope of the genetic counselling role continues to evolve alongside these changes. We present an exemplary role for genetic counsellors in a highly specialised service within England's National Health Service for people who have or are suspected to have rare genetic types of Ehlers Danlos syndrome. The service employs genetic counsellors and consultants from the fields of genetics and dermatology. The service also works closely with other specialists and related charities and patient organisations. The genetic counsellors in the service provide routine genetic counselling such as diagnostic and predictive testing, but their role also includes the writing of patient literature and emergency and well-being resources, delivering workshops and talks, and the development of qualitative and quantitative research on the patient experience. Data from such research has informed the development of patient self-advocacy and supportive resources, raised awareness amongst healthcare professionals and enhanced the standard of care and outcomes for patients. The service aims to be an example of innovation and accessibility and provides a model that can be potentially adopted by other highly specialised services of rare genetic diseases.

Detection of the Copy Number Variants of Genes in Patients with Familial Cardiac Diseases by Massively Parallel Sequencing

INTRODUCTION

The implication of copy number variations in familial heart disease is known, although in-depth knowledge is lacking; hence, more studies are needed to further our understanding. Massively parallel sequencing, thanks to its recent surge in use, is emerging as a valid tool for the detection of this type of variant, through the use of appropriate software.

METHODS

We conducted a study with 182 patients diagnosed with mendelian cardiovascular diseases who underwent sequencing using a cardiac gene panel and then a specific calling process for copy number variations (CNVs) with ExomeDepth software, which provides us with a Bayes factor (BF), a score of the probability that a CNV detected is true.

RESULTS

After a rigorous CNV prioritization process, we confirmed the variants obtained by MLPA or SNP-based array, finding three real CNVs in five individuals in the MYH11, FBN1 and PDMI7 genes.

CONCLUSION

The confirmed CNVs present in all cases BF values > 60, thus establishing a threshold to consider real CNVs in the calling process carried out by ExomeDepth on our gene panel.

The role of cutaneous manifestations in the diagnosis of the Ehlers-Danlos syndromes

The Ehlers-Danlos syndromes (EDS) comprise a group of inherited connective tissue disorders presenting with features of skin hyperextensibility, joint hypermobility, abnormal scarring and fragility of skin, blood vessels and some organs. The disease is generally diagnosed through the cluster of clinical features, though the addition of genetic analysis is the gold standard for diagnosis of most subtypes. All subtypes display skin manifestations, which are essential to the accurate clinical diagnosis of the condition. Furthermore, cutaneous features can be the first and/or only presenting feature in some cases of EDS and thus understanding these signs is vital for diagnosis. This review focuses on particular cutaneous features of each EDS subtype and their clinical importance. Provision of a specific diagnosis is important for management, prognosis and genetic counselling, often for family members beyond the individual.

Recurrent pneumothorax in a case of tenascin-X deficient Ehlers-Danlos syndrome: Broadening the phenotypic spectrum

The genomic region surrounding the Tenascin‐XB gene (TNXB) is a complex and duplicated region, with several pseudogenes that predispose to high rates of homologous recombination. Classical‐like Ehlers–Danlos syndrome (clEDS) is the result of tenascin‐X deficiency due to biallelic loss of function variants in the TNXB gene. Here we present a patient with clEDS and spontaneous pneumothorax, a feature not previously reported to be associated with this condition. Two inherited pathogenic/likely pathogenic variants were identified; a previously reported deletion resulting in a TNXA/TNXB chimeric gene and a novel frameshift variant. The Tenascin‐XB gene is well described in the literature to be associated with collagen metabolism, stabilization of the fibrillar‐collagen matrix and is expressed abundantly in the extracellular matrix. We propose that tenascin‐X deficiency is directly related to pneumothorax predisposition. This case expands the phenotypic spectrum of clEDS and highlights the challenges with molecular analysis and diagnosis

Ehlers-Danlos Syndromes, Joint Hypermobility and Hypermobility Spectrum Disorders

Ehlers-Danlos syndrome is an umbrella term for a clinically and genetically heterogeneous group of hereditary soft connective tissue disorders mainly featuring abnormal cutaneous texture (doughy/velvety, soft, thin, and/or variably hyperextensible skin), easy bruising, and joint hypermobility. Currently, musculoskeletal manifestations related to joint hypermobility are perceived as the most prevalent determinants of the quality of life of affected individuals. The 2017 International Classification of Ehlers-Danlos syndromes and related disorders identifies 13 clinical types due to deleterious variants in 19 different genes. Recent publications point out the possibility of a wider spectrum of conditions that may be considered members of the Ehlers-Danlos syndrome community. Most Ehlers-Danlos syndromes are due to inherited abnormalities affecting the biogenesis of fibrillar collagens and other components of the extracellular matrix. The introduction of next-generation sequencing technologies in the diagnostic setting fastened patients' classification and improved our knowledge on the phenotypic variability of many Ehlers-Danlos syndromes. This is impacting significantly patients' management and family counseling. At the same time, most individuals presenting with joint hypermobility and associated musculoskeletal manifestations still remain without a firm diagnosis, due to a too vague clinical presentation and/or the lack of an identifiable molecular biomarker. These individuals are currently defined with the term "hypermobility spectrum disorders". Hence, in parallel with a continuous update of the International Classification of Ehlers-Danlos syndromes, the scientific community is investing efforts in offering a more efficient framework for classifying and, hopefully, managing individuals with joint hypermobility.

Animal Models of Ehlers-Danlos Syndromes: Phenotype, Pathogenesis, and Translational Potential

The Ehlers–Danlos syndromes (EDS) are a group of heritable connective tissues disorders mainly characterized by skin hyperextensibility, joint hypermobility and generalized tissue fragility. Currently, 14 EDS subtypes each with particular phenotypic features are recognized and are caused by genetic defects in 20 different genes. All of these genes are involved in the biosynthesis and/or fibrillogenesis of collagens at some level. Although great progress has been made in elucidating the molecular basis of different EDS subtypes, the pathogenic mechanisms underlying the observed phenotypes remain poorly understood, and consequentially, adequate treatment and management options for these conditions remain scarce. To date, several animal models, mainly mice and zebrafish, have been described with defects in 14 of the 20 hitherto known EDS-associated genes. These models have been instrumental in discerning the functions and roles of the corresponding proteins during development, maturation and repair and in portraying their roles during collagen biosynthesis and/or fibrillogenesis, for some even before their contribution to an EDS phenotype was elucidated. Additionally, extensive phenotypical characterization of these models has shown that they largely phenocopy their human counterparts, with recapitulation of several clinical hallmarks of the corresponding EDS subtype, including dermatological, cardiovascular, musculoskeletal and ocular features, as well as biomechanical and ultrastructural similarities in tissues. In this narrative review, we provide a comprehensive overview of animal models manifesting phenotypes that mimic EDS with a focus on engineered mouse and zebrafish models, and their relevance in past and future EDS research. Additionally, we briefly discuss domestic animals with naturally occurring EDS phenotypes. Collectively, these animal models have only started to reveal glimpses into the pathophysiological aspects associated with EDS and will undoubtably continue to play critical roles in EDS research due to their tremendous potential for pinpointing (common) signaling pathways, unveiling possible therapeutic targets and providing opportunities for preclinical therapeutic interventions.

Clinical and molecular characteristics of 168 probands and 65 relatives with a clinical presentation of classical Ehlers-Danlos syndrome

Classical Ehlers-Danlos syndrome (cEDS) is a heritable connective tissue disorder mainly caused by pathogenic variants in COL5A1 or COL5A2, encoding type V collagen. Its diagnosis, based on clinical criteria and molecular confirmation, can be challenging. We report the molecular and clinical characteristics of 168 probands (72 clinically evaluated at our center) and 65 relatives with a clinical presentation of cEDS. Type V collagen defects were found in 145 probands, 121 (83.5%) were located in COL5A1 and 24 (16.5%) in COL5A2. Although 85.6% of molecularly confirmed patients presented the two major clinical criteria (generalized joint hypermobility, hyperextensible skin with atrophic scarring), significant inter- and intrafamilial phenotypic variability was noted. COL5A2 variants often caused a more severe phenotype. Vascular complications were rare in individuals with type V collagen defects (1.4%). Among the 72 probands clinically evaluated in our center, the mutation detection rate was 82.0%. The majority (68.1%) harbored COL5A1/COL5A2 defects. Yet, 13.9% harbored a defect in another gene (COL1A1, PLOD1, TNXB, AEBP1) highlighting important clinical overlap and the need for molecular confirmation of the diagnosis as this has implications regarding follow-up and genetic counseling. Eighteen percent of the 72 probands remained molecularly unexplained and a COL5A1 variant of unknown significance was identified in 6.9%.

Ehlers-Danlos Syndrome in the Field of Psychiatry: A Review

Ehlers-Danlos syndrome (EDS) comprises a series of rare hereditary connective tissue diseases characterized by joint hypermobility, joint dislocation, and hyperextensibility of the skin, as well as cardiovascular involvement. EDS is often associated with chronic widespread physical pain, which can lead to psychological pain. Poor awareness and limited diagnosis of EDS and related symptoms result in decreased self-esteem and confusion regarding physical sensation. Furthermore, EDS imposes substantial psychological burden on patients due to exercise restriction, scars, keloids, and subcutaneous fat accumulation on the extremities, which leads to parental overprotection and bullying experiences from other children at school age. Recent large-scale studies have suggested that patients with EDS have a higher risk of mood disorders than the general population. Other cohort studies indicated high prevalence of anorexia nervosa, addiction, obsessive compulsive disorder, and anxiety disorder were found in patients with EDS. Case reports instead indicated that some psychiatric disorders were secondary symptoms due to physical problems from EDS. Therefore, psychiatrists must be more knowledgeable and proactive about EDS in their practice. We review the previous case reports and literature for patients with EDS, along with our own case of complicated psychiatric problems, which are strongly related to early stressful situations through childhood and adolescence. This is to aid general psychiatrists in the discussion of appropriate medical management in such infrequent, yet challenging conditions.

The Roles of Tenascins in Cardiovascular, Inflammatory, and Heritable Connective Tissue Diseases

Tenascins are a family of multifunctional extracellular matrix (ECM) glycoproteins with time- and tissue specific expression patterns during development, tissue homeostasis, and diseases. There are four family members (tenascin-C, -R, -X, -W) in vertebrates. Among them, tenascin-X (TNX) and tenascin-C (TNC) play important roles in human pathologies. TNX is expressed widely in loose connective tissues. TNX contributes to the stability and maintenance of the collagen network, and its absence causes classical-like Ehlers-Danlos syndrome (clEDS), a heritable connective tissue disorder. In contrast, TNC is specifically and transiently expressed upon pathological conditions such as inflammation, fibrosis, and cancer. There is growing evidence that TNC is involved in inflammatory processes with proinflammatory or anti-inflammatory activity in a context-dependent manner. In this review, we summarize the roles of these two tenascins, TNX and TNC, in cardiovascular and inflammatory diseases and in clEDS, and we discuss the functional consequences of the expression of these tenascins for tissue homeostasis.