The ultrastructural and histophotometric study of elastic and collagen fibers in type II Ehlers-Danlos syndrome and subclinical forms

The Role of Cell Adhesion and Cytoskeleton Dynamics in the Pathogenesis of the Ehlers-Danlos Syndromes and Hypermobility Spectrum Disorders

The Ehlers-Danlos syndromes (EDS) are a group of 13 disorders, clinically defined through features of joint hypermobility, skin hyperextensibility, and tissue fragility. Most subtypes are caused by mutations in genes affecting the structure or processing of the extracellular matrix (ECM) protein collagen. The Hypermobility Spectrum Disorders (HSDs) are clinically indistinguishable disorders, but are considered to lack a genetic basis. The pathogenesis of all these disorders, however, remains poorly understood. Genotype-phenotype correlations are limited, and findings of aberrant collagen fibrils are inconsistent and associate poorly with the subtype and severity of the disorder. The defective ECM, however, also has consequences for cellular processes. EDS/HSD fibroblasts exhibit a dysfunctional phenotype including impairments in cell adhesion and cytoskeleton organization, though the pathological significance of this has remained unclear. Recent advances in our understanding of fibroblast mechanobiology suggest these changes may actually reflect features of a pathomechanism we herein define. This review departs from the traditional view of EDS/HSD, where pathogenesis is mediated by the structurally defective ECM. Instead, we propose EDS/HSD may be a disorder of membrane-bound collagen, and consider how aberrations in cell adhesion and cytoskeleton dynamics could drive the abnormal properties of the connective tissue, and be responsible for the pathogenesis of EDS/HSD.

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.

Multiple triggering in a girl with Ehlers-Danlos syndrome: case report

We report a case of multiple triggering associated with Ehlers-Danlos syndrome. We postulate that the propensity for tendon degeneration in Ehlers-Danlos syndrome coupled with repetitive microtrauma might lead to fraying of the tendon fibers and, consequently, triggering. Indeed, in our case, debridement of the tendons rather than resection of A1 pulley resulted in a good long-term functional outcome 2 years after surgery.

Collagen fibril arabesques in connective tissue disorders

BACKGROUND

In various connective tissue disorders, collagen fibrils and elastic fibers may exhibit some ultrastructural abnormalities.

OBJECTIVE

This electron microscopy study focused on collagen fibril orientation and unusual shapes in the dermis of Ehlers-Danlos syndrome (EDS) and related entities, including spontaneous cervical artery dissection syndrome and recurrent preterm premature rupture of fetal membranes syndrome.

RESULTS

In addition to some abnormal fibril shapes typically found in these syndromes, other conformations (hook shaped, S shaped, ring shaped) that have not been illustrated previously in the literature were observed.

CONCLUSION

The abnormal collagen fibril conformations observed in EDS and other related conditions characterized by tissue fragility likely affect both the internal cohesiveness of the bundles and the mechanobiologic properties of the tissue.

Ullrich congenital muscular dystrophy: connective tissue abnormalities in the skin support overlap with Ehlers-Danlos syndromes

Ullrich congenital muscular dystrophy (UCMD) is caused by mutations in the three genes coding for the alpha chains of collagen VI and characterized by generalized muscle weakness, striking hypermobility of distal joints in conjunction with variable contractures of more proximal joints, and normal intellectual development. The diagnosis is supported by abnormal immunoreactivity for collagen VI on muscle biopsies. As patients with UCMD show clinical characteristics typical of classical disorders of connective tissue such as Ehlers-Danlos syndromes (EDS), we investigated the ultrastructure of skin biopsy samples from patients with UCMD (n=5). Electron microscopy of skin biopsies revealed ultrastructural abnormalities in all cases, including alterations of collagen fibril morphology (variation in size and composite fibers) and increase in ground substance, which resemble those seen in patients with EDS. Our findings suggest that there is a true connective tissue component as part of the phenotypic spectrum of UCMD and that there is considerable clinical as well as morphological overlap between UCMD and classic connective tissue disorders.