Understanding the basis of Ehlers-Danlos syndrome in the era of the next-generation sequencing

Ocular manifestations in Ehlers-Danlos syndrome

BACKGROUND/OBJECTIVE

To provide a large-scale analysis on the demographics and ocular comorbidities in Ehlers-Danlos Syndrome (EDS) patients in the US.

SUBJECTS/METHODS

This is an exploratory cross-sectional study comparing medical records of EDS patients to the general population on demographic variables and ICD-10 ocular diagnoses. A research platform with de-identified EHR data of over 99 million patients across 60 healthcare organizations was utilized. Groups were stratified by 30-year age groups. Patients aged 0-61+ with an ICD-10 diagnosis of EDS (76,526), the general platform population aged 0-61+ (99,836,639), and patients with a concurrent ICD-10 ocular diagnosis were queried to determine the prevalence of EDS across demographic variables, ocular disease, and odds of ocular disease. Statistical analysis was conducted using Microsoft Excel and R studio, using p < 0.01 and 95% confidence intervals (CI).

RESULTS

An EDS diagnosis was most prevalent in white females aged 0-30 years old (259.6 per 100,000). The majority of ocular diagnoses were more prevalent in the 0-60-year-old EDS population compared to the general population including myopia (5227.0 per 100,000) and dry eye (4211.6 per 100,000). Overall, diagnoses of angioid streaks (POR 18.72, 95% CI 10.32, 33.94) and idiopathic intracranial hypertension (IIH) (POR 18.43, 95% CI 17.51, 19.39) showed the highest increased odds in patients with EDS while significantly decreased odds were shown for type 2 diabetic retinopathy, age-related macular degeneration, and retinal vein occlusion.

CONCLUSIONS

EDS was associated with increased odds of having a concurrent ocular pathology, suggesting that, upon diagnosis of EDS, referral to ophthalmology may be valuable.

Gaining Insights into Inherited Bleeding Disorders of Complex Etiology in Pediatric Patients: Whole-Exome Sequencing as First-Line Investigation Tool

INTRODUCTION

 Investigation of the molecular basis of inherited bleeding disorders (IBD) is mostly performed with gene panel sequencing. However, the continuous discovery of new related genes underlies the limitation of this approach. This study aimed to identify genetic variants responsible for IBD in pediatric patients using whole-exome sequencing (WES), and to provide a detailed description and reclassification of candidate variants.

MATERIAL AND METHODS

 WES was performed for 18 pediatric patients, and variants were filtered using a first-line list of 290 genes. Variant prioritization was discussed in a multidisciplinary team based on genotype-phenotype correlation, and segregation studies were performed with available family members.

RESULTS

 The study identified 22 candidate variants in 17 out of 18 patients (94%). Eleven patients had complete genotype-phenotype correlation, resulting in a diagnostic yield of 61%, 5 (28%) were classified as partially solved, and 2 (11%) remained unsolved. Variants were identified in platelet (ACTN1, ANKRD26, CYCS, GATA1, GFI1B, ITGA2, NBEAL2, RUNX1, SRC, TUBB1), bleeding (APOLD1), and coagulation (F7, F8, F11, VWF) genes. Notably, 9 out of 22 (41%) variants were previously unreported. Variant pathogenicity was assessed according to the American College of Medical Genetics and Genomics guidelines and reclassification of three variants based on family segregation evidence, resulting in the identification of 10 pathogenic or likely pathogenic variants, 6 variants of uncertain significance, and 6 benign or likely benign variants.

CONCLUSION

 This study demonstrated the high potential of WES in identifying rare molecular defects causing IBD in pediatric patients, improving their management, prognosis, and treatment, particularly for patients at risk of malignancy and/or bleeding due to invasive procedures.

Type 1 collagen: Synthesis, structure and key functions in bone mineralization

Collagen is a highly abundant protein in the extracellular matrix of humans and mammals, and it plays a critical role in maintaining the body's structural integrity. Type I collagen is the most prevalent collagen type and is essential for the structural integrity of various tissues. It is present in nearly all connective tissues and is the main constituent of the interstitial matrix. Mutations that affect collagen fiber formation, structure, and function can result in various bone pathologies, underscoring the significance of collagen in sustaining healthy bone tissue. Studies on type 1 collagen have revealed that mutations in its encoding gene can lead to diverse bone diseases, such as osteogenesis imperfecta, a disorder characterized by fragile bones that are susceptible to fractures. Knowledge of collagen's molecular structure, synthesis, assembly, and breakdown is vital for comprehending embryonic and foetal development and several aspects of human physiology. In this review, we summarize the structure, molecular biology of type 1 collagen, its biomineralization and pathologies affecting bone.

Prevalence and quality of temporomandibular disorders, chronic pain and psychological distress in patients with classical and hypermobile Ehlers-Danlos syndrome: an exploratory study

BACKGROUND

The Ehlers-Danlos syndromes are a group of clinically and genetically heterogeneous hereditary diseases affecting the connective tissue. They are characterized by hypermobility of the joints, hyperextensible skin and friable tissue. According to current classification, 13 subtypes can be distinguished, of which the hypermobile and the classical subtype are the most prevalent. This study aimed to evaluate patients with classical (cEDS) and hypermobile (hEDS) Ehlers-Danlos syndrome regarding temporomandibular disorder (TMD), chronic pain, and psychological distress.

METHODS

Support groups from Germany, Austria, and Switzerland were contacted, and social media were used to recruit participants. Free text questions, the German version of the Depression Anxiety and Stress Scale (DASS), and the German version of the Graded Chronic Pain Status (GCPS) were used.

RESULTS

259 participants were included (230 hEDS/29 cEDS). At least 49.2% of the participants had painful or restricted jaw movements, and at least 84.9% had pain in the masticatory muscles, with 46.3% already having a diagnosed TMD. Multivariate analysis showed a significant correlation between TMJ involvement and chronic pain with a 2.5-fold higher risk of chronic pain with a diagnosed TMD. 22.8% of participants had a critical score for depression, 53.3% had a critical score for anxiety, and 34.0% had a critical score for stress.

CONCLUSION

There is a high prevalence of TMD problems and chronic pain in patients with cEDS and hEDS. The lack of knowledge about these problems can create psychological distress. More research is needed to provide adequate treatment for patients with EDS.

Novel Homozygous ADAMTS2 Variants and Associated Disease Phenotypes in Dogs with Dermatosparactic Ehlers-Danlos Syndrome

Tissue fragility, skin hyperextensibility and joint hypermobility are defining characteristics of Ehlers-Danlos syndrome (EDS). Human EDS is subclassified into fourteen types including dermatosparactic EDS, characterized by extreme skin fragility and caused by biallelic ADAMTS2 mutations. We report two novel, ADAMTS2 variants in DNA from EDS-affected dogs. Separate whole-genome sequences from a Pit Bull Terrier and an Alapaha Blue Blood Bulldog each contained a rare, homozygous variant (11:2280117delC, CanFam3.1), predicted to produce a frameshift in the transcript from the first coding ADAMTS2 exon (c.10delC) and a severely truncated protein product, p.(Pro4ArgfsTer175). The clinical features of these dogs and 4 others with the same homozygous deletion included multifocal wounds, atrophic scars, joint hypermobility, narrowed palpebral fissures, skin hyperextensibility, and joint-associated swellings. Due to severe skin fragility, the owners of all 6 dogs elected euthanasia before the dogs reached 13 weeks of age. Cross sections of collagen fibrils in post-mortem dermal tissues from 2 of these dogs showed hieroglyphic-like figures similar to those from cases of severe dermatosparaxis in other species. The whole-genome sequence from an adult Catahoula Leopard Dog contained a homozygous ADAMTS2 missense mutation, [11:2491238G>A; p.(Arg966His)]. This dog exhibited multifocal wounds, atrophic scars, and joint hypermobility, but has survived for at least 9 years. This report expands the spectrum of clinical features of the canine dermatosparactic subtype of EDS and illustrates the potential utility of subclassifying canine EDS by the identity of gene harboring the causal variant.

Case report: Characterization of a rare pathogenic variant associated with loss of COL3A1 expression in vascular Ehlers Danlos syndrome

The vascular subtype of Ehlers Danlos Syndrome (vEDS) is a rare connective tissue disorder characterized by spontaneous arterial, bowel or organ rupture. The diagnosis of vEDS is established in a proband by identification of a heterozygous pathogenic variant in the alpha-1 gene of type III collagen (COL3A1) by molecular analysis. In this report, we present a case of vEDS with life threatening, spontaneous arterial dissections in association with an uncharacterized rare variant of COL3A1, exon19:c.1340G > A. Primary culture of patient skin fibroblasts followed by immunofluorescence revealed a complete absence of COL3A1 protein expression as well as altered morphology. Electron microscopy of the cultured fibroblasts showed abnormal vacuoles in the cytoplasm suggestive of a secretory defect. In this study, we have performed functional characterization of the COL3A1 exon19:c.1340G > A variant for the first time and this may now be classified as likely pathogenic in vEDS.

Connective Tissue Disorders and Cardiovascular Complications: The Indomitable Role of Transforming Growth Factor-β Signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that segregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. With overwhelming evidence of the involvement of aberrant Transforming Growth Factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in the relationship between connective tissue disorders and their associated cardiovascular complications. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, the heritable connective tissue syndromes related to aberrant TGF-β signaling, and will discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

Rare neurological manifestations in a Saudi Arabian patient with Ehlers-Danlos syndrome and a novel homozygous variant in the TNXB gene

We report a 38-year-old Saudi male with Ehlers-Danlos Syndrome (EDS). The patient presented with rare and unusual neurological manifestations, including but not limited to ophthalmoplegia and myopathic pattern on his electromyography. In addition to hand weakness, there was skin hyperextensibility, joint hyperflexibility, and frontal baldness. Next-generation sequencing was performed on target exon sequences, using whole exome sequencing and Burrows-Wheeler Aligner for alignment/base calling. Genome Analysis Toolkit and reference genome Homo sapiens (UCSC hg19) were used for sequence processing and analysis. Variant classification was done according to standard international recommendations. A novel homozygous variant, NM_019105.6: c.8488C>T p.(Gln2830*), was detected in the TNXB gene. This variant is not reported in the literature nor dbSNP or gnomAD databases. Additionally, this variant is predicted to create a premature stop codon and produce a truncated protein or nonsense-mediated mRNA decay. Hence, it is classified as a likely pathogenic variant. The same point variant was found in a heterozygous state in the patient's father and sister. Both presented with milder symptoms associated with Ehlers-Danlos syndromes and heritable connective tissue disorders. Therefore, the patient was diagnosed as a tenascin-X (TNX) deficient type of EDS known as classical-like Ehlers-Danlos syndrome. TNX deficient patients may present with clinical and electrophysiological manifestations that are unusual in EDS like frontal baldness, ophthalmoplegia, and myotonia, which mimic myotonic dystrophy type I. Clinicians should be aware of the potential overlap of symptoms among these two diseases to ensure correct diagnosis is made.

Biomarkers for Ehlers-Danlos Syndromes: There Is a Role?

Ehlers-Danlos syndromes (EDS) are an inherited heterogeneous group of connective tissue disorders characterized by an abnormal collagen synthesis affecting skin, ligaments, joints, blood vessels, and other organs. It is one of the oldest known causes of bruising and bleeding, and it was described first by Hippocrates in 400 BC. In the last years, multiple gene variants involved in the pathogenesis of specific EDS subtypes have been identified; moreover, new clinical diagnostic criteria have been established. New classification models have also been studied in order to differentiate overlapping conditions. Moreover, EDS shares many characteristics with other similar disorders. Although distinguishing between these seemingly identical conditions is difficult, it is essential in ensuring proper patient care. Currently, there are many genetic and molecular studies underway to clarify the etiology of some variants of EDS. However, the genetic basis of the hypermobile type of EDS (hEDS) is still unknown. In this review, we focused on the study of two of the most common forms of EDS-classic and hypermobile-by trying to identify possible biomarkers that could be of great help to confirm patients' diagnosis and their follow up.

Occupational Therapy Interventions for Clients with Ehlers-Danlos Syndrome (EDS) in the Presence of Postural Orthostatic Tachycardia Syndrome (POTS)

Postural orthostatic tachycardia syndrome (POTS) is often seen in clients with Ehlers-Danlos syndrome (EDS), primarily hypermobile EDS. Research has shown clients with EDS and POTS may experience limitations affecting not only their physical function, but also their social, emotional, and mental well-being. Using a client-centered approach, occupational therapy practitioners assess health, well-being, symptomatology (fatigue, muscle pain, dizziness, etc.), participation and engagement in occupation, and provide interventions to improve quality of life. This paper will address occupational therapy interventions to treat common symptomatology for clients with EDS in the presence of POTS, including environmental modifications, use of adaptive equipment and orthoses, exercise and fall prevention, energy conservation and pacing, sleep hygiene, and routine and habit development to promote optimal engagement in meaningful occupations.

Molecular mechanisms and clinical manifestations of rare genetic disorders associated with type I collagen

Type I collagen is an important structural protein of bone, skin, tendon, ligament and other connective tissues. It is initially synthesized as a precursor form, procollagen, consisting of two identical pro-α1(I) and one proα2(I) chains, encoded by COL1A1 and COL1A2, respectively. The N- and C- terminal propeptides of procollagen are cleavage by N-proteinase and C-proteinase correspondingly, to form the central triple helix structure with Gly-X-Y repeat units. Mutations of COL1A1 and COL1A2 genes are associated with osteogenesis imperfecta, some types of Ehlers-Danlos syndrome, Caffey diseases, and osteogenesis imperfect/Ehlers- Danlos syndrome overlapping diseases. Clinical symptoms caused by different variations can be variable or similar, mild to lethal, and vice versa. We reviewed the relationship between clinical manifestations and type I collagen - related rare genetic disorders and their possible molecular mechanisms for different mutations and disorders.