Although widespread pain is the identifying feature of fibromyalgia (FM), its underlying mechanism is still issue of controversy. Whereas previous studies showed central nervous system abnormalities (e.g. increased excitability of the pain matrices and dysfunction of the descending modulatory system), recent studies identified a small-fibre damage.
In this case-control study using clinical, neurophysiological and morphometric investigations we aim at identifying frequency and characteristics of small-fibre damage in patients with fibromyalgia. We will also investigate voltage-gated sodium channel genotyping, to detect possible gain-of-function mutations.
Patients will be enrolled in the Rheumatology Unit of Fibromyalgia diagnosis and therapy (Clinical Medicine Department) and in the Neuromuscular Diseases Unit (Department of Human Neuroscience) of Policlinico Umberto I, Sapienza University, Rome. Each subject will undergo rheumatological, neurological examination and clinical questionnaires, Nerve Conduction Study to assess large-fibre function, laser evoked potentials recording, quantitative sensory testing and skin biopsy to test small fibres. In the skin biopsy investigation we will use a composite panel of immunostaining including PGP9.5, GAP43, TRPV1, TRPV4. In patients with small-fibre damage, as assessed with skin biopsy. we will also collect blood sample for genotyping voltage-gated sodium channels.
Our study aims at assessing the frequency and characteristics of small-fibre damage in a large cohort of patients through a complete diagnostic workup including clinical, neurophysiological and morphometric examinations. Furthermore, for the first time, this study, using different immunostaining, will assess the role of the different small-fibres in the skin. We will also investigate the genotyping of voltage-gated sodium channels, whose alterations have been demonstrated in small-fibre neuropathies.
Therefore we believe that our findings might be useful to better understand the prevalence and the characteristics of small-fibre damage in FM and to improve our understanding on pain physiopathology in this complex condition.
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