Fibromyalgia (FM) is characterized by chronic diffuse pain and affects 0.5 to 5% of the population, with a higher prevalence in women1. This condition is characterized by joint and muscle pain, also associated with fatigue, migraine, sleeps disorders, depression and irritable bowel syndrome2. The presentation of these various symptoms varies greatly from one patient to another, with great heterogeneity in clinical, physical, social, psychological and therapeutic responses. . A recent parliamentary inquiry report called for recognition of the disease and recommended to build a unified care path for patients; a collective expertise is led by INSERM to help in patient care. Faced with the heterogeneity of FM, several international studies have attempted to identify subgroups of patients based essentially on clinical symptoms of the disease3-8, including a recent Korean study of 313 patients9, which suggested four groups, but with methodological limitations, not taking into account the new criteria10 for evaluating FM.

Recent studies have also shown that there is a peripheral neuropathic component in the mechanisms of this pathology, demonstrated by a decrease in the density of the epidermal nerve fibers11-12, called small fiber neuropathy (SFN) neuropathy. It is an attack of small sensory and sympathetic nerve fibers, causing pain, paresthesia as well as disturbances of the autonomous system. Other studies also suggested that a significant proportion of patients diagnosed with fibromyalgia had SFN, demonstrated by cutaneous biopsy13-14 or confocal microscopy of the cornea15. A new device, the Sudoscan®, makes it possible to detect a SFN much simpler, faster and less invasive than the technique of ophthalmology or biopsy. Although this Sudoscan® test has been used extensively in conditions such as diabetes16-19, no study has been used to assess the presence of SFN in FM.

The aim of this pilot study is to identify the prevalence of SFN in FM patients, using this new non-invasive device, in order to have a better defined representation of the prevalence of small-fiber neuropathy in an FM population compared to a group of healthy volunteer matched in age, sex, BMI and by menopausal status for women.

Only one visit (2 to 3h) :

Inclusion of the patient Clinical examination ; evaluation of pain for FM patients Measurement of the electrochemical conductance of the hands and feet using Sudoscan® Evaluation of quality of life, anxiety, depression, sleep quality, fatigue, catastrophizing and social precarity End of study

Inclusion Criteria:

• - Patient over 18 years of age and under 65 years of age,
• Male or female patient,
• Patient with fibromyalgia (according to the ACR criteria of 2016),
• Cooperation and understanding sufficient to comply with the requirements of the study,
• Acceptance of written consent,
• Affiliation to the French Social Security system.

Inclusion criteria healthy subjects:

• Subject of more than 18 years,
• Woman or man,
• Healthy voluntary non-painful subjects matched by age (+/- 5 years), by sex, by BMI (+/- 10%) and by menopausal status for women,
• Cooperation and understanding sufficient to comply with the requirements of the study,
• Acceptance of written consent,
• Affiliation to the French Social Security system,
• Registration or acceptance of registration in the National Register of Volunteers participating in research.

Exclusion Criteria:

• Exclusion criteria patients:
• Patient with a physical inability to place the palms of the hands or the soles of the feet on the electrodes of Sudoscan®,
• Patient with a medical and / or surgical history judged by the investigator or his representative to be incompatible with the test (in particular a disease known to give neuropathies of small fibers: diabetes, Gougerot-Sjögren's disease, vasculitis, sarcoidosis, chronic ethylism ...),
• Pregnant or nursing woman
• Patient participating in another clinical trial, or in a period of exclusion, or having received a total amount of compensation in excess of EUR 4500 over the 12 months preceding the start of the trial,
• Patient benefiting from a measure of legal protection (curatorship, guardianship, safeguard of justice ...),
• Patient not affiliated to the French Social Security system.

Exclusion criteria healthy subjects :

• Physical inability to place the palms of the hands or the soles of the feet on the electrodes of Sudoscan®.
• Medical and / or surgical history judged by the investigator or his representative to be incompatible with the test,
• Pregnant or nursing woman
• Participating in another clinical trial, or within the exclusion period, or having received a total amount of compensation in excess of EUR 4500 over the 12 months preceding the start of the trial,
• Cooperation and an understanding that does not permit strict compliance with the conditions laid down in the Protocol,
• Benefiting from a measure of legal protection (curatorship, guardianship, safeguard of justice ...),
• Not affiliated to the French Social Security system.

No masking