LAUSR

Editor, The suffix -dynia derived from Ancient Greek οdύmg (“sorrow, grief, anguish”) forms medical terms relating to pain. The general term of allodynia defined a condition where the discomfort sensation is stimulated that does not normally elicit pain. This sensation has been never described on nails. In this report, we described a case series of five female patients with painful sensation on the digits and nails after an aesthetic treatment of removal and application of semi-permanent nail polish exacerbated by mechanical and thermic trauma. All patients are Caucasian female, with a mean age of 47 years (range 35–51). They complained of pain and feeling of warmth at the fingernails during the aesthetic treatment caused by the excessive mechanical trauma. In two patients, the mechanical trauma was so excessive as to induce a complete destruction of the distal part of the nail, on the 3rd finger of the right hand and on the 5th finger of the left, respectively, with subsequent erosion of the nail bed. Clinically, at the first examination, the patients showed a red-purple discoloration of the nail bed and the disappearance of the lunula (Fig. 1a). Onychoscopy showed a marked dilatation of the capillaries in the distal half of the nail with visible superficial glomus bodies (Fig. 1b). All patients reported a pain sensation on the fingernails, defined such as paresthesia or hyperesthesia, intense and resistant to treatment. The term paresthesia is considered a variant of “neuropathic pain” characterized by the appearance of an annoying or painful sensation following various stimuli that usually do not cause pain. Symptoms of neuropathic pain, including hyperesthesia, develop secondary to a disease or injury of the central or peripheral nervous system that results in abnormal functioning of the somatosensory system. Peripheral sensitization most often occurs after inflammation of a peripheral nerve and results in a reduced threshold for activation and hyperexcitability of primary afferent neurons. This occurs due to post-translational changes and expression of the transient receptor potential subfamily V (TRPV1) that occurs after nerve damage. After these changes, peripheral nerves are more sensitive to mechanical and thermal stimuli. Mechanical trauma is known as a possible cause of hyperesthesia from peripheral neurologic injury. The occurrence of paresthesia/hyperesthesia of the fingernails following the application of semi-permanent nail polish has been known for years. 5 In case of allergic contact dermatitis to methylene-methacrylate, hyperesthesia results from a direct neurological damage by this resin; in case of hyperesthesia, without the development of contact allergy, the cause is attributable to mechanical damage to peripheral nerve fibres induced by a too aggressive manicure. Thanks to onychoscopy, a non-invasive method, is possible to observe at high magnification the aspect of the capillaries of nail bed. The observation of dilated capillaries with the presence of glomus bodies is a sign of damage to the underline vessels and together with the history of a trauma and the symptom reported by patient could be diagnostic of a paresthesia on nails. Surely, further study on a higher number of patients with this painful sensation after manicure and a confront versus patients without any symptoms after the manicure is needed to confirm this hypothesis. In conclusion, we proposed to use the term of onychodynia to identify this painful sensation on the nails after a mechanical trauma.