In patients with small fibre neuropathy a statistically significant increase of TRPV1 expression on epidermal keratinocytes was reported [97] The skin biopsies from patients with complex regional pain syndrome (CRPS) or postherpetic neuralgia (PHN) were analysed, and the samples exhibited Nav1.1, Nav1.2, Nav1.5, Nav1.6, and Nav1.7 and Nav1.8 immunolabeling, which was not present in normal skin [91]. This evidence concerns the gene SCN9A and complex regional pain syndrome.