Evaluation of the Role of Serum Tenascin-X Levels in the Diagnosis of Hypermobile Ehlers-Danlos Syndrome

Thirteen types of EDS have been described based on their clinical manifestations and genetic backgrounds. Their diagnosis relies on personal and family medical history, together with established clinical criteria. A definitive diagnosis can then be confirmed through genetic testing. However, definitive diagnosis of hypermobile Ehlers-Danlos syndrome (hEDS), the most common EDS subtype (\>80% of cases), remains impossible because its molecular basis is still unknown. The diagnosis of hEDS is based on a set of clinical criteria, some of which are subject to examiner interpretation. These criteria have limitations at the extremes of age and in mild or incomplete forms, potentially preventing a formal diagnosis. Patients may consequently experience a diagnostic odyssey and psychological distress, without recognition of their condition or access to appropriate management. The diagnosis of hEDS is further complicated by the overlap between its clinical manifestations and those of Hypermobility Spectrum Disorders (HSD), which are relatively common in the general population (1-3%). HSD are also characterized by joint hypermobility, which may be complicated by joint instability and pain, but unlike hEDS, they are not associated with tissue fragility. There is therefore an urgent need to identify a reliable, simple, reproducible, and widely accessible diagnostic criterion to establish a diagnosis of hEDS in the large population of hypermobile patients. Tenascin-X (TN-X) is a glycoprotein involved in the assembly of the ECM. One study showed that TN-X levels were reduced by 35% in 52% of hypermobile patients (9/17) compared with healthy controls. This finding suggests a possible association between serum TN-X levels and hEDS. However, no correlation has yet been investigated. We hypothesize that serum TN-X levels could serve as a biological diagnostic criterion for hEDS.