Small-fibre neuropathies and skin: news and perspectives for dermatologists.

Small-fibre neuropathies (SFNs) can be defined as diseases of small nerve fibres. Because their symptoms are mainly located in the skin in the initial stages, dermatologists may frequently be confronted with these diseases. Moreover, skin biopsies and the subsequent measurement of intraepidermal nerve fibre density have become a widely accepted technique to investigate the structural integrity of small nerve fibres. The pathogenesis of injury to small nerve fibres is poorly understood. It probably depends on the cause. SCN9A-gene variants have been reported. Diabetes mellitus is one of the main causes of SFNs. Some causes of SFNs are very well-known to dermatologists: Gougerot-Sjögren syndrome, lupus, sarcoidosis and Fabry disease. We also discuss erythermalgia, prurigo nodularis, nummular eczema, burning mouth syndrome and sensitive skin as SFNs.