A new serum-profiling study is bringing molecular evidence to one of the most difficult diagnostic questions in connective-tissue medicine: how closely are hypermobile Ehlers–Danlos syndrome and hypermobility spectrum disorders biologically related? Using a technology known as proximity extension assay, researchers identified shared patterns of circulating proteins in people diagnosed with hypermobile Ehlers–Danlos syndrome, or hEDS, and those classified as having hypermobility spectrum disorders, or HSD. The findings suggest that the two conditions may occupy overlapping biological territory rather than representing entirely separate disorders, while also demonstrating how blood-based proteomics could help investigate diseases that are currently diagnosed mainly through clinical assessment.
Hypermobile Ehlers–Danlos syndrome is the most common form of Ehlers–Danlos syndrome, a group of inherited or suspected inherited connective-tissue conditions associated with joint hypermobility, tissue fragility, pain and a range of systemic symptoms. Unlike several other Ehlers–Danlos subtypes, hEDS does not yet have a widely accepted molecular diagnostic test. HSD is used when a person has clinically significant joint hypermobility and related symptoms but does not meet the full criteria for hEDS or another defined connective-tissue disorder. In practice, the distinction can be complicated, because symptoms such as chronic pain, fatigue, gastrointestinal dysfunction, autonomic complaints and soft-tissue injuries may occur across both groups.
The study, published in Clinical Proteomics, examined serum proteins using proximity extension assay-based profiling. Serum is the liquid portion of blood that remains after clotting and contains thousands of proteins released by immune cells, blood vessels, connective tissues and other organs. These molecules can reflect inflammation, tissue repair, vascular function, metabolism and immune regulation. Rather than measuring one protein at a time, the proximity extension assay uses pairs of antibodies linked to short DNA tags. When both antibodies bind near their target protein, the DNA tags can be joined or extended, producing a molecular signal that is amplified and quantified with highly sensitive genomic methods.
This approach allows researchers to measure panels of proteins from very small sample volumes, often with greater analytical sensitivity than conventional immunoassays. The resulting data are not simply a list of elevated or reduced proteins. They form a multidimensional molecular profile in which correlated changes may reveal biological pathways active in a disease. In the context of hEDS and HSD, such profiling is especially valuable because the disorders are clinically heterogeneous. Two patients may share generalized joint hypermobility but differ substantially in pain, fatigue, immune symptoms, gastrointestinal manifestations or autonomic dysfunction. A serum signature could therefore provide clues about shared mechanisms while also helping researchers explore biologically distinct patient subgroups.
The investigators reported that people with hEDS and HSD displayed overlapping serum protein signatures. This convergence is important because the relationship between the two diagnoses has remained a subject of clinical debate. The result does not mean that hEDS and HSD are identical, nor does it establish that every patient with one condition will have the same molecular profile. Instead, it indicates that both groups may involve common biological processes detectable in the circulation. The shared signature could reflect interconnected changes in extracellular-matrix regulation, immune signaling, vascular biology, tissue maintenance or cellular stress, although the precise interpretation depends on the individual proteins and pathways identified in the full analysis.
For patients, the promise of this research lies in the possibility of moving beyond a purely symptom-based framework. At present, clinicians diagnose hEDS by evaluating joint mobility, characteristic features, personal and family history, and the exclusion of other conditions. There is no definitive blood test for hEDS, and the absence of a biomarker can contribute to delayed diagnosis, uncertainty and inconsistent access to care. A validated protein panel would not replace clinical judgment, but it could eventually support diagnosis, improve classification and help distinguish hEDS or HSD from other causes of widespread pain and joint instability. That possibility remains prospective: the current findings represent a research signal, not a ready-to-use clinical assay.
The study also highlights both the power and the limitations of modern proteomics. High-throughput assays can identify statistically meaningful differences across groups, but a protein signature is not automatically a disease-specific fingerprint. Circulating proteins may be influenced by age, sex, body composition, medication, recent infection, exercise, sleep, diet and coexisting inflammatory or metabolic disorders. Because hEDS and HSD frequently occur alongside other chronic conditions, researchers must determine which molecular changes are directly related to hypermobility-associated biology and which reflect comorbidities or treatment. Replication in larger, independent cohorts will be essential, as will standardized clinical definitions and carefully matched control groups.
Another challenge is the difference between association and mechanism. If a protein is consistently altered in people with hEDS or HSD, that finding may indicate a biological consequence of the condition rather than its cause. For example, long-term pain, reduced physical activity or repeated tissue injury could modify immune and repair pathways in the blood. Conversely, an altered protein network might contribute to abnormal extracellular-matrix organization, impaired proprioception or vascular symptoms. Follow-up studies using cell models, tissue analysis and longitudinal sampling will be needed to determine whether the proteins are drivers, consequences or measurable companions of the disorders.
The findings may also influence how researchers think about the boundary between syndromes defined by clinical criteria. In medicine, diagnostic categories are useful when they reliably predict biology, prognosis or treatment response. If hEDS and HSD repeatedly show common molecular patterns, the conditions may be better understood as overlapping points within a broader hypermobility-related spectrum. At the same time, molecular overlap does not erase clinically meaningful differences. Future studies could reveal subgroups distinguished by inflammatory activity, connective-tissue remodeling, autonomic regulation or pain-processing pathways. Such stratification could eventually support more personalized care, matching patients with therapies according to biological features rather than diagnosis alone.
For now, the serum proteomic results provide an important step toward understanding a group of disorders that has often been investigated through anatomy and symptoms rather than molecular biology. Proximity extension assay technology gives researchers a sensitive way to survey the protein landscape and search for reproducible signals shared by hEDS and HSD. The next phase will require larger prospective studies, repeated measurements over time and comparison with healthy participants and other connective-tissue conditions. If the observed signatures withstand that testing, they could become the foundation for biomarker development, improved diagnostic confidence and a more coherent biological model of hypermobility-related disease.
Subject of Research: Shared serum protein signatures in hypermobile Ehlers–Danlos syndrome and hypermobility spectrum disorders
Article Title: Proximity extension assay-based serum proteomic profiling identifies shared protein signatures in hypermobile Ehlers–Danlos syndrome and hypermobility spectrum disorders
Article References: Published in Clinical Proteomics, Springer Nature, 2026
Image Credits: AI Generated
DOI: 10.1186/s12014-026-09588-2
Keywords: hypermobile Ehlers–Danlos syndrome, hypermobility spectrum disorders, serum proteomics, proximity extension assay, biomarkers, connective tissue, molecular profiling, clinical proteomics
