Measurement of intra epidermal nerve fibre density (IENFD) is a relatively simple assay which can be performed in relatively innocuous 3mm punch biopsies of skin, a routine dermatological investigation. Its utility in the assessment of small fibre function in peripheral neuropathies is clear. Peripheral neuropathies of diverse aetiologies are associated with reduced epidermal innervation density. The investigators have extensive experience in this technique which has minimal morbidity and would like to establish in painful channelopathies whether the anatomy of C-fibres innervating the skin is normal. Patients can opt out of this and still be included in the study. Fibroblasts can be cultured from 4mm skin biopsy (obtained as described above). These represent a useful tool in the future as a source of cells the phenotype of which can be modulated for instance to generate induced pluripotent stem cells followed by induction of neural crest differentiation in order to understand the molecular basis of altered pain perception. A further approach is to isolate neural crest stem cells directly from hair follicles a technique pioneered by Prof Sieber-Blum at Newcastle University. The investigators subsequently aim to generate sensory neurons from these cells and compare the behaviour of sensory neurons from control subjects to those generated from patients with heritable pain syndromes.