Chronic pain in patients with the hypermobility type of Ehlers-Danlos syndrome: evidence for generalized hyperalgesia

Background: The Ehlers-Danlos Syndrome (EDS) is one the most prevalent heritable connective tissue disorders. Generalized severe joint hypermobility, which is frequently associated with joint dislocations, chronic joint and limb pain, and premature osteoarthritis, are the dominant clinical manifestations of the hypermobility type of EDS (EDS-HT). Chronic widespread pain is highly present in this patient group, but up to now, evidence for generalized hyperalgesia is lacking. Several studies in chronic pain disorders examined whether central hyperexcitability could be existent by using algometry. Purpose: The primary objective of the study was to investigate whether pressure pain thresholds (PPTs) at both symptomatic and asymptomatic body areas differ in EDS-HT patients compared to healthy subjects. In addition, we examined the type of chronic pain EDS-HT patients experience. Methods: Twenty-three women with EDS-HT and 23 gender- and age-matched healthy controls participated. All subjects marked on Margolis Pain Diagram where they felt pain lasting longer than 24 hours in the past 4 weeks. Then, they completed several questionnaires assessing pain cognitions (Pain Catastrophizing Scale, Pain Vigilance and Awareness Questionnaire, Hospital Anxiety and Depression Scale), fatigue (Checklist Individual Strength subscale fatigue), disability (Health Assessment Questionnaire), and general health status (Short Form Health Survey-36), in order to take the possible influence of these factors on PPTs into account. Patients also completed the Pain Detect Questionnaire regarding the severity, course, quality and nature of the pain they experienced. Thereupon, a blinded researcher assessed PPTs at 14 body locations on the trunk and extremities. The pressure was gradually increased at a rate of 1kg/s until the subject indicated that the pain level has been reached. The threshold was determined as the mean of the 2 last values out of the 3 consecutive measurements. This method has been found to be efficient and reliable in the exploration of pathophysiological mechanisms involved in pain. PPTs were compared for the 2 complete groups. In addition, PPTs of patients and controls who did not report pain in a respective zone were compared. Results: The EDS-HT patient group demonstrated significantly lower PPTs compared to the control group for all zones. The mean (SD) PPT was 2.9 (1.62) kg/cm2 in the EDS-HT patients and 5.2 (1.88) kg/cm2 in the controls (P