Functional and histological improvements of small nerve neuropathy after high-concentration capsaicin patch application: A case study

Introduction:Small fiber neuropathy has been found to occur in a large variety of pathological onditions, and the gold standard for diagnosis of small fiber neuropathy is skin biopsy. Sudorimetry is now considered an accurate technique to evaluate small fiber function with a good sensitivity and specificity for the diagnosis of small fiber neuropathy. Capsaicin high-concentration patch is approved for the treatment of peripheral neuropathic pain in adults either alone or in combination with other medicinal products for pain.Methods:We describe the case of a 50-year-old woman diagnosed with small fiber neuropathy. After 2 previous treatment failures, she was proposed a treatment with high-dose capsaicin patches on the sole of her foot. The patient experienced an important diminution of her neuropathic pain. There was a 50% decrease in the pain numeric scale. Electrochemical skin conductance and skin biopsy were repeated 3 months after patch application.Results:At 3 months, the patient then experienced an important diminution of her neuropathic pain, electrochemical skin conductance had normalized both in the hands and feet and intraepidermal nerve fiber density at distal leg increased almost reaching normal range.Conclusion:This case report shows the correlation between clinical improvement, electrochemical skin conductance normalization, and intraepidermal nerve fiber density improvement after a high-dose capsaicin patch in a patient with small fiber neuropathy.