Characterization of small fiber neuropathy in hypermobile Ehlers Danlos Syndrome

Abstract

Hypermobile Ehlers Danlos Syndrome (hEDS)/hypermobility spectrum disorders (HSD) are incapacitating and painful syndromes involving a generalized connective tissue disorder with joint hypermobility and musculoskeletal complications. A neuropathic component is clinically likely given frequent burning sensations, hypoesthesia, or allodynia. Small fiber neuropathy (SFN) refers to the dysfunction or damage of A-δ and C-fibers, which relay thermal and nociceptive information as well as mediating autonomic function. SFN has been suggested by prior studies in hEDS but these early findings (case series N≤20) with sole reliance on intraepidermal nerve fiber density (IENFD) called for a larger sample combined with functional testing.In this retrospective chart extraction from 79 hEDS/HSD patients referred to a pain center due to neuropathic pain or dysautonomia, both functional (Quantitative Sensory Testing (QST), N=79) and structural (IENFD, N=69) evaluations of small nerve fibers were analyzed in combination with clinical data and standardized questionnaires.All the patients reported moderate to severe pain interfering with daily life. A decreased thermal detection (QST) was shown in 55/79 patients (70%) and a decreased IENFD in 54/69 patients (78%). Hence a small fiber neuropathy (both abnormal IENFD and QST) was definite in 40/69 patients (58%), possible in 23/69 patients (33%) and excluded in only 6/69 patients (9%).These results add strong evidence for a peripheral neuropathic contribution to pain symptoms in hEDS/HSD, in addition to the known nociceptive and central sensitization components. Such neuropathic contribution could raise the hypothesis of a neurological cause of hEDS, the only EDS syndrome still without a known genetic cause. Hence, our data is leading the way to a better stratification of this very heterogeneous population, which could improve symptom management and expand pathophysiological research.