To assess the Intraepidermal nerve fiber density (IENFD) in patients diagnosed with Fibromyalgia (FM) and to evaluate the role of IgM binding to Trisulfated heparin disaccharide (TS-HDS) in these patients.

FM is a poorly understood pain disorder with several proposed pathophysiologic mechanisms. It is characterized by widespread pain, fatigue and sleep abnormalities¹.Small fiber neuropathy (SFN) has been proposed as an underlying mechanism and patients with FM have been shown to have a reduction in the IENFD^2,3.   An underlying inflammatory process which could be a result of autoimmune phenomena has also, been suggested⁴. Non-length dependent small fiber neuropathy (NLDSFN) has been shown to have a higher incidence of autoimmune disease⁵.

Twenty-two patients with established diagnosis of FM underwent skin biopsy at 2 sites; 10 cms above the lateral malleolus and 10 cms above the patella. Serum IgM binding to TS-HDS were assayed using an ELISA method.

5/22 patients had positive TS-HDS antibodies; of these, 4 had NLDSFN (p=0.0393). Comparison with a control group at Washington University showed no significant difference in presence of TS-HDS antibodies (p= 0.41). However, when compared with large database of patients with NLDSFN, there was a trend to significance (p= 0.06). 

This study further supports hypothesis that a subgroup of FM patients has SFN. We suggest a correlation between the presence of NLD-SFN and TS-HDS antibodies.