Fibromyalgia and Small Fiber Neuropathy

Inclusion Criteria: * patients over 18 years of age with no age limit - * having given their signed consent to take part in the study * affiliated to the French social security system * able to be followed for the entire duration of the study * reading and understanding French * accepting the principle of the study and able to comply with its conditions * suffering from chronic pain for at least six months of at least moderate intensity (≥ 4/10) * fibromyalgia detected by the FiRST questionnare and defined by the revised diagnostic criteria of the WHO or chronic nociceptive or nociplastic pain without associated fibromyalgia. * chronic pain for at least 6 months of at least moderate intensity (≥ 4/10) * untreated or with stable analgesic treatment for at least 2 weeks prior to inclusion- normal neurological examination at inclusion Exclusion Criteria: * litigation or compensation-seeking * cancer for less than 2 years * known cause of small-fiber neuropathy such as diabetes, systemic disease, hypothyroidism, alcohol, renal failure, genetic disease * clinical or EMG neuropathy * peripheral or central nervous system pathology with or without associated neuropathic pain * uncontrolled chronic pathology such as : morbid obesity, sleep apnea, uncontrolled hypertension, etc. - psychosis, previous suicide attempt * drug or psychoactive substance abuse * cognitive or psychological disorders incompatible with compliance with and/or understanding of the protocol * participation in another biomedical research protocol.