Outcome of small fibers pathology in fibromyalgia: a real life longitudinal observational study.

OBJECTIVES: Small fibers pathology is frequently described in fibromyalgia (FM), but its evolution and its role in clinical outcome of the disease are unclear. This longitudinal observational real-life study aimed to monitor the evolution of skin nerve fiber density in FM, in view of clinical data.

METHODS: Sixty-two FM patients were controlled by means of skin biopsy and clinical assessment after 18 months of follow-up.

RESULTS: At T0 intraepidermal nerve fiber density (IENFD) was normal in 10 patients, reduced at thigh-proximal-site in 46 cases and decreased at proximal and foot-distal-site in 6 patients. At follow up-T1-the IENFD was unchanged, while Brief Pain Inventory-BPI-pain sub score, DN4 and fatigue were improved. Reduced IENFD at proximal and distal sites, together with fatigue and BPI-motor and work sub scores were predictors of more severe disability measured with Fibromyalgia Impact Questionnaire (FIQ) at T1. Reduced IENFD influenced a minor effect of drugs-antiepileptics and/or antidepressants, and physical exercise on fatigue.

CONCLUSIONS: Small fibers impairment seems stable in medium term in FM. A possible influence of small fibers dysfunction on motor performance could have a role in FM evolution. The beneficial effect of physical exercise could be limited in patients with reduced IENFD.