Small‐fibre damage is associated with distinct sensory phenotypes in patients with fibromyalgia and small‐fibre neuropathy

Abstract

Background: In this clinical and psychophysical study, we aimed to verify whether patients with fibromyalgia with and without small‐fibre pathology and patients with pure small‐fibre neuropathy share common sensory phenotypes. Methods: Using an algorithm based on quantitative sensory testing variables, we grouped 64 consecutive patients with fibromyalgia (20 with small‐fibre pathology, 44 without) and 30 patients with pure small‐fibre neuropathy into different sensory phenotypes: sensory loss, thermal hyperalgesia, mechanical hyperalgesia and healthy phenotypes. Results: We found that the frequency of the different sensory phenotypes differed markedly between patients with fibromyalgia and patients with small‐fibre neuropathy. In patients with fibromyalgia, with and without small‐fibre pathology, healthy and hyperalgesia phenotypes (both thermal and mechanical) were similarly represented, whilst sensory loss and mechanical hyperalgesia phenotypes were the most frequent phenotypes in patients with small‐fibre neuropathy. Conclusions: Our findings indicate that small‐fibre damage is associated with distinct sensory phenotypes in patients with fibromyalgia and in patients with small‐fibre neuropathy. The lack of phenotype differences between patients with fibromyalgia with and without small‐fibre pathology and the relatively high frequency of the healthy phenotype in these patients highlight a complex relationship between small‐fibre pathology and pain in patients with fibromyalgia.