Understanding itch: An update on mediators and mechanisms of pruritus.

Pruritus is the most common symptom secondary to skin diseases. Advances in the fi elds of neurobiology, immunology and physiology have made it possible for us to understand and unravel the deeper pathophysiological basis of pruritus. This review aims to update our current understanding of the mechanisms and mediators of pruritus. Special attention is paid to endogenous itch mediators particularly newly identifi ed ones like endovanilloids, opioids, neurotrophins, cannabinoids, proteases and cytokines. Various theories explaining the peripheral encoding of itch are reviewed. Multiple neural pathways including the central itch pathways as well as supraspinal processing of itch and brain areas involved in pruritus are highlighted. Apart from peripheral itch mediators, spinal neural receptors are also involved in control of itch and should form part of the development of a novel antipruritic strategy. Further studies are required to fi ll the lacunae in our current understanding of the pathophysiology of pruritus.

Pruritus: still a challenge / Prurido: ainda um desafio

Pruritus is a symptom that may be associated with a wide array of diseases - skin diseases, systemic diseases or even those without a defined cause. According to its severity and evolution, it may compromise the patients' quality of life in a significant way. New therapeutic approaches, in which histamine release is not the main event, are being described for pruritus control. Therefore, taking into account the origin of the mediators of pruritus, we conducted a review of the available resources emphasizing that, although very important, anti-histamines are not the answer for every kind of pruritus.

Prurido é um sintoma que pode estar associado a uma gama ampla de patologias, sejam elas cutâneas, sistêmicas ou mesmo sem causa definida . Conforme sua intensidade e evolução pode comprometer de forma significativa a qualidade de vida dos pacientes. Novas abordagens terapêuticas estão sendo descritas para o controle do prurido, onde a liberação da histamina não é o fator principal. Assim, baseando-se na origem de seus mediadores, faz-se uma revisão desses recursos e ressalta-se que, embora de grande importância no arsenal terapêutico, os anti-histamínicos não são a panacéia para todos os tipos de prurido.

Avaliação da associação entre as alterações no metabolismo mineral e o prurido nos pacientes em hemodiálise / Evaluating the association between alterations in mineral metabolism and pruritus in hemodialysis patients

FUNDAMENTOS: prurido é o sintoma mais freqüente nos pacientes nefropatas em hemodiálise. Parâmetros laboratoriais anormais têm sido encontrados, com dados conflitantes. OBJETIVO: relacionar a prevalência de prurido com alterações no metabolismo mineral de pacientes em hemodiálise. MÉTODOS: estudo caso-controle. Avaliados 105 pacientes, sendo os pacientes com prurido os casos, preencheram o questionário do protocolo de pesquisa e a escala análoga visual, os dados laboratoriais foram coletados dos prontuários eletrônicos. RESULTADOS: a média de idade foi de 51,9 anos, 59 por cento dos pacientes eram homens e 43 por cento dos pacientes tinham prurido. Xerodermia ocorreu em 45 por cento dos pacientes. Níveis elevados de Ca foram demonstrados em 55 por cento dos pacientes e 47 por cento tinham prurido. Quanto ao fósforo 60 por cento tinham valores elevados e 43 por cento tinham prurido. A relação Ca/P foi normal em todos. O paratormônio mostrou-se elevado em 95 por cento dos pacientes, todos referindo prurido. CONCLUSÃO: houve associação estatisticamente significativa entre o grupo de pacientes com prurido e xerodermia. Os níveis séricos de Cálcio, Fósforo, relação Ca/P, PTHi e o tamanho do dialisador não apresentaram associação estatisticamente significativa com o prurido. Logo, encontramos relação importante entre xerodermia e prurido, sem relação com os parâmetros laboratoriais avaliados.

BACKGROUND: Uremic pruritus is the most frequent symptom in long-term hemodialysis patients. Abnormal laboratory parameters have been found with conflicting data. OBJECTIVE: To correlate the prevalence of pruritus with alterations in mineral metabolism in hemodialysis patients. METHODS: This was a case-control study. A hundred and five patients on maintenance hemodialysis were evaluated: a group of patients with pruritus and a control group. They answered a research protocol questionnaire; laboratory data were collected from medical records and the patients with pruritus filled out a visual analogue scale (VAS) to measure pruritus level. RESULTS: The mean age was 51.9 years; 59 percent of the patients were men and 43 percent of the patients had pruritus. Xeroderma occurred in 45 percent of the patients. High levels of calcium were demonstrated in 55 percent of the patients and 47 percent had pruritus. 60 percent of the patients had high phosphorus levels and 43 percent had pruritus. The Ca/P ratio was normal for all the patients. Parathyroid hormone was high in 95 percent of the patients, all of them referring pruritus. CONCLUSION: There was a statistically significant association between the group of patients with pruritus and xeroderma. Serum calcium and phosphorus levels, Ca/P ratio, PTHi and size of the dialyzer did not show a statistically significant association with pruritus. Therefore, we found an important relationship between xeroderma and pruritus, with no relation with the assessed laboratory parameters.