Light and Electron Microscopy of Classical Ehlers–Danlos Syndrome

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.

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.

Classic Ehlers–Dalnos syndrome presenting as atypical chronic haematoma: a case report with novel frameshift mutation in COL5A1

Background

Ehlers–Danlos syndrome (EDS) is a group of inherited connective tissue disorders characterized by skin hyperextensibility, joint hypermobility and soft tissue vulnerable to blunt injury. Early recognition and diagnosis are crucial to patients to provide appropriate treatment, as well as to screen for life-threatening conditions such as aortic dissection and hollow organ perforation. The diagnosis of EDS is made based on clinical presentations, skin biopsy, and electron microscopy findings. To date, mutations in at least 20 genes have been found to cause the Ehlers-Danlos syndromes. However, EDS is still underestimated due to lack of awareness of its variable clinical presentations. Here we reported an EDS case with atypical initial presentation and a novel genetic mutation.

Case presentation

This 4-year-old Taiwanese male patient presented with easy bruising, multiple ecchymoses, joint hypermobility, hyperextensible skin, and prolonged pretibial haematoma. He was initially suspected of a bleeding tendency due to coagulation disorders. The coagulation test results were normal. DNA sequencing was performed for molecular diagnosis. Subsequently, the diagnosis of classical EDS was made by identifying a novel frameshift mutation in COL5A1 [NM_000093.4:c.4211_4212delAG, p.Gln1404Arg]. This mutation in the type V collagen gene COL5A1 contributes to the phenotype of classical EDS. This novel frameshift mutation may disturb the structural stability of collagen V and interfere with its heparin binding capacity, explaining the chronic haematoma.

Conclusion

The reported case showed the unusual features of chronic haematoma. This novel frameshift mutation and its phenotype correlation can provide useful information for practitioners about early recognition in Ehlers–Danlos syndrome.

Hanoverian F/W-line contributes to segregation of Warmblood fragile foal syndrome type 1 variant PLOD1:c.2032G>A in Warmblood horses

BACKGROUND

Warmblood fragile foal syndrome (WFFS) is a lethal condition detected in Warmblood horses. Its origin and association with performance traits and fertility among horse populations is unknown.

OBJECTIVES

To validate the previously identified WFFS type 1 (WFFST1)-associated missense variant PLOD1:c.2032G>A and to investigate its distribution among various horses with particular focus on Hanoverian breed, as well as its pathomorphological picture. The study aimed at identifying the origin of the mutant allele and its correlation with performance and fertility traits in Warmblood horses.

STUDY DESIGN

Retrospective case-control and association study.

METHODS

WFFST1 variant was validated using whole genome sequencing (WGS) in 78 equids. In an affected foal with a homozygous mutant genotype, necropsy was performed. Skin samples were examined using histology and transmission electron microscopy. Pathway analysis was performed to trace back 81 genetic carriers to the most common recent ancestor. Furthermore, generalised linear model analysis was employed to test estimated breeding values (EBVs) for differences in performance and fertility traits among different genotypes in Hanoverian horses.

RESULTS

WFFST1 variant had the lowest minor allele frequency among all variants detected in WGS data in the region of PLOD1. Further genotyping of this variant revealed allele frequencies of 0.14 in Hanoverian horses. Histological investigations of the WFFST1-affected foal showed loosely arranged collagen fibres in the dermis. Ultrastructurally, multifocal areas with degraded collagen fibrils and fibrillar plaques were detected. Further pathway analysis revealed a stallion from the Hanoverian sire F/W line as the most common recent ancestor of all tested genetic carriers. Furthermore, WFFST1 variant was found to be correlated with EBVs for gait-related traits as well as conformation and dressage.

MAIN LIMITATIONS

Study evaluated carriers and cases only from Europe.

CONCLUSIONS

This study provides a comprehensive evaluation of WFFST1 variant and traces it back to its potential origin.

Absence of Collagen Flowers on Electron Microscopy and Identification of (Likely) Pathogenic COL5A1 Variants in Two Patients

Two probands are reported with pathogenic and likely pathogenic COL5A1 variants (frameshift and splice site) in whom no collagen flowers have been identified with transmission electron microscopy (TEM). One proband fulfils the clinical criteria for classical Ehlers-Danlos syndrome (cEDS) while the other does not and presents with a vascular complication. This case report highlights the significant intrafamilial variability within the cEDS phenotype and demonstrates that patients with pathogenic COL5A1 variants can have an absence of collagen flowers on TEM skin biopsy analysis. This has not been previously reported in the literature and is important when evaluating the significance of a TEM result in patients with clinically suspected cEDS and underscores the relevance of molecular analysis.

Electron microscopy in the diagnosis of Ehlers-Danlos syndromes: correlation with clinical and genetic investigations

BACKGROUND

The Ehlers-Danlos syndromes (EDS) consist of 13 subtypes with overlapping features including joint hypermobility, skin and vascular fragility and generalized connective tissue friability. As DNA analysis has become the gold standard for investigation of EDS, transmission electron microscopy (TEM) in clinical practice is decreasing. However, owing to the use of next-generation sequencing, the frequency of variants of uncertain significance (VUS) identified using DNA analysis is increasing. We hypothesized that TEM can provide evidence for or against pathogenicity of VUS.

OBJECTIVES

The aim of this study was to evaluate the role of TEM in the diagnosis of EDS subtypes.

METHODS

Data were collected from patients who underwent a skin biopsy between October 2012 and March 2017 at the London EDS National Diagnostic Service. TEM biopsies were categorized as 'normal' or 'abnormal' according to the description and conclusion in the TEM reports. Definitive diagnoses were reached via a combination of clinical features, structural and functional studies and DNA investigations.

RESULTS

The analysis included 177 patients, comprising 30 abnormal and 147 normal TEM reports. A definitive diagnosis of monogenic EDS subtypes was made in 24 patients. Overall, 17 of these 24 patients (71%) had an abnormal biopsy report and seven (29%) had a normal biopsy report. No TEM findings were specifically associated with any EDS subtype, although collagen flowers were present in most patients with a genetically confirmed diagnosis of classical EDS.

CONCLUSIONS

TEM analysis of collagen structure may have the potential to provide evidence for or against the pathogenicity of a VUS, but more work is needed to establish a clear role for TEM in this process. What's already known about this topic? Collagen fibril abnormalities can be seen in several Ehlers-Danlos syndrome (EDS) subtypes. What does this study add? This study provides clinical data, transmission electron microscopy (TEM) data and molecular data of one of the largest groups of patients suspected to have a monogenetic EDS subtype. No TEM findings were specifically associated with an EDS subtype. There was a higher percentage (71%) of abnormal biopsy findings in patients with a definitive diagnosis of a monogenetic EDS subtype and where a class 4/5 genetic variant was present.

Skeletal muscle morphology, protein synthesis, and gene expression in Ehlers-Danlos syndrome

Patients with Ehlers-Danlos syndrome (EDS) are known to have genetically impaired connective tissue and skeletal muscle symptoms in form of pain, fatigue, and cramps; however earlier studies have not been able to link these symptoms to morphological muscle changes. We obtained skeletal muscle biopsies in patients with classic EDS [cEDS; n = 5 (Denmark)+ 8 (The Netherlands)] and vascular EDS (vEDS; n = 3) and analyzed muscle fiber morphology and content (Western blotting and muscle fiber type/area distributions) and muscle mRNA expression and protein synthesis rate (RT-PCR and stable isotope technique). The cEDS patients did not differ from healthy controls (n = 7-11) with regard to muscle fiber type/area, myosin/α-actin ratio, muscle protein synthesis rate, or mRNA expression. In contrast, the vEDS patients demonstrated higher expression of matrix proteins compared with cEDS patients (fibronectin and MMP-2). The cEDS patients had surprisingly normal muscle morphology and protein synthesis, whereas vEDS patients demonstrated higher mRNA expression for extracellular matrix remodeling in skeletal musculature compared with cEDS patients.NEW & NOTEWORTHY This study is the first of its kind to systematically investigate muscle biopsies from Ehlers-Danlos patients, focusing on muscle structure and function. These patients suffer from severe muscle symptoms, but in our study they show surprisingly normal muscle findings, which points toward indirect muscle symptoms originating from the surrounding connective tissue. These findings have basal physiological importance and implications for future physiotherapeutic treatment options for these patients.