Skin biopsy for the diagnosis of peripheral neuropathy

Skin biopsy has become an accepted tool for investigating small nerve fibres, which are invisible to conventional neurophysiological tests even though they are affected early on in peripheral neuropathies of varying aetiology. Morphometric analysis of epidermal and dermal nerves has proved to be reliable, reproducible and unaffected by the severity of neuropathy, making skin biopsy useful for diagnosing small fibre neuropathy (SFN) in clinical practice. The possibility of obtaining skin biopsy specimens from different sites of the body, to repeat them within the area of the same sensory nerve, to distinguish between somatic and autonomic nerves and to investigate the expression of nerve-related proteins has widened the potential applications of this technique to clinical research. Skin biopsy performed using a minimally invasive disposable punch is a safe and painless procedure. Using specific antibodies with bright-field immunohistochemistry or immunofluorescence technique, it is possible to investigate unmyelinated fibres innervating the epidermis of hairy and glabrous skin, large myelinated fibres supplying specialized corpuscles in glabrous skin, and autonomic fibres innervating sweat glands, blood vessels and arrector pilorum muscles. This review discusses the features of skin innervation in hairy and glabrous skin, the functional properties of skin nerve fibres and their changes in peripheral neuropathies.