Pain
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We aimed to investigate whether small-fibre pathology, a common skin biopsy finding in patients with fibromyalgia, implies clinically important abnormalities of somatosensory system function and verify whether it is associated with voltage-gated sodium channel variants. In 57 consecutively enrolled patients with fibromyalgia, we used skin biopsy to distinguish patients with and without small-fibre pathology. In all patients, we assessed somatosensory system function using quantitative sensory testing (QST) and laser-evoked potentials and investigated voltage-gated sodium channel genotyping. ⋯ The SCN9A variant, found in a patient with small-fibre pathology, was an already profiled gain-of-function mutation, previously reported in small-fibre neuropathy. Our findings suggest that small-fibre pathology has a negligible impact on somatosensory system function in fibromyalgia. The genetic analysis suggests that patients with rare small-fibre neuropathy due to voltage-gated sodium channel variants may be misdiagnosed as patients with fibromyalgia.