Neurophysiologie des Pruritus

Pruritus: an overview of current concepts

Pruritus is an integral part of the patient's symptoms in numerous dermatological and systemic diseases in humans and animals. Comparable to chronic pain, pruritus can have a dramatic impact on the quality of life of the patient. In recent years, pruritus has been defined as an autonomous, pain-independent sensation, and itch-specific neurons, mediators, spinal neurons and cortical areas have been identified. These observations have not only improved our understanding of the neurobiology of itch but will also lead to improved diagnosis and to the development of new and more efficient therapeutic options. This article reviews the role of itch fibres and their response to various mediators of pruritus including histamine, vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), and substance P (SP), and opioids. Substances that may be involved in the induction or modulation of itch may be termed pruritogenic mediators and examples discussed include proteases, lipid mediators, neuropeptides, opioids and various cytokines. There is no single, generally accepted clinical classification of chronic pruritus. In the past pruritus has been classified on the basis of the neuroanatomical origin and on the potential underlying disease. Therapeutic options for the management of pruritus are discussed including topical and systemic therapies, assuming that trigger factors have been eliminated where possible. Topical agents may include capsaicin, the calcineurin inhibitors tacrolimus and pimecrolimus, and cannabinoid agonists such as N-palmitoyl ethanolamine. Systemic therapies may include antihistamines, anticonvulsants, opiate receptor antagonist or agonists, antidepressants, ciclosporin, and UV light.

Antipruritic effect of cyclosporine microemulsion in prurigo nodularis: results of a case series

BACKGROUND

Prurigo nodularis shows intense itching nodules, which are often persistent and therapy refractory. Histological alterations include fibrosis of collagen fibers and presence of inflammatory infiltrate, which partly explains the clinical persistence of lesions. Inflammatory cells may directly contribute to induction and maintenance of pruritus at nerve fibers. Cyclosporine microemulsion (ME) suppresses the migration and proliferation of inflammatory cells and may thereby interfere with pathogenesis of prurigo nodularis. The aim of this investigation was to assess the antipruritic efficiency of cyclosporine ME in therapy of prurigo nodularis.

PATIENTS AND METHODS

14 patients with prurigo nodularis of diverse origin and failure to previous therapy were treated with oral cyclosporine ME (3 to 5 mg per kg daily). Blood pressure, liver enzymes, renal function and differential blood count were monitored.

RESULTS

In 13 of 14 prurigo patients (92.9 %) there was a significant response to monotherapy with cyclosporine ME. The maximal antipruritic effect occurred after 2 weeks to 12 months. Prurigo nodules also healed during therapy. Seven patients (50.0 %) described side effects. In one case the therapy was stopped.

CONCLUSIONS

Oral cyclosporine ME is an effective therapy for prurigo nodularis of diverse origin. It appears to function by inhibiting dermal inflammatory cells.

Chronischer Pruritus

Chronic pruritus (starting from 6 weeks duration) is symptom of dermatological, internal, neurological or psychiatric disease. Identification and treatment of the underlying diseases is of great importance especially in the initial phase of chronic pruritus in order to prevent peripheral and central sensitization processes and thus chronification. Application of the redefined clinical classification, newly defined clinical algorithms and inquiry of clinical characteristics of pruritus is helpful in finding the underlying disease. In chronic pruritus existing for several years, clarifying the underlying origin is difficult and therapies are often ineffective. Next to conventional therapies such as antihistamines and corticosteroids, central effective substances can be applied preventing pruritus sensation on spinal or cerebral level.