Association of mast-cell-related conditions with hypermobile syndromes: a review of the literature.

Ehlers-Danlos syndrome (EDS) is a group of related connective tissue disorders consisting of 13 subtypes, each with its own unique phenotypic and genetic variation. The overlap of symptoms and multitude of EDS variations makes it difficult for patients to achieve a diagnosis early in the course of their disease. The most common form, hypermobile type EDS (hEDS) and its variant, hypermobile spectrum disorder (HSD), are correlated with rheumatologic and inflammatory conditions. Evidence is still needed to determine the pathophysiology of hEDS; however, the association among these conditions and their prevalence in hEDS/HSD may be explained through consideration of persistent chronic inflammation contributing to a disruption of the connective tissue. Aberrant mast cell activation has been shown to play a role in disruption of connective tissue integrity through activity of its mediators including histamine and tryptase which affects multiple organ systems resulting in mast cell activation disorders (MCAD). The overlap of findings associated with MCAD and the immune-mediated and rheumatologic conditions in patients with hEDS/HSD may provide an explanation for the relationship among these conditions and the presence of chronic inflammatory processes in these patients. It is clear that a multidisciplinary approach is required for the treatment of patients with EDS. However, it is also important for clinicians to consider the summarized symptoms and MCAD-associated characteristics in patients with multiple complaints as possible manifestations of connective tissue disorders, in order to potentially aid in establishing an early diagnosis of EDS.

Independent COL5A1 Variants in Cats with Ehlers-Danlos Syndrome.

We investigated four cats with similar clinical skin-related signs strongly suggestive of Ehlers-Danlos syndrome (EDS). Cases no. 1 and 4 were unrelated and the remaining two cases, no. 2 and 3, were reportedly siblings. Histopathological changes were characterized by severely altered dermal collagen fibers. Transmission electron microscopy in one case demonstrated abnormalities in the collagen fibril organization and structure. The genomes of the two unrelated affected cats and one of the affected siblings were sequenced and individually compared to 54 feline control genomes. We searched for private protein changing variants in known human EDS candidate genes and identified three independent heterozygous COL5A1 variants. COL5A1 is a well-characterized candidate gene for classical EDS. It encodes the proα1 chain of type V collagen, which is needed for correct collagen fibril formation and the integrity of the skin. The identified variants in COL5A1 are c.112_118+15del or r.spl?, c.3514A>T or p.(Lys1172*), and c.3066del or p.(Gly1023Valfs*50) for cases no. 1, 2&3, and 4, respectively. They presumably all lead to nonsense-mediated mRNA decay, which results in haploinsufficiency of COL5A1 and causes the alterations of the connective tissue. The whole genome sequencing approach used in this study enables a refinement of the diagnosis for the affected cats as classical EDS. It further illustrates the potential of such experiments as a precision medicine approach in animals with inherited diseases.