Pruriplastic Itch-A Novel Pathogenic Concept in Chronic Pruritus

Psychodermatology of Chronic Pruritus: An Overview of the Link Between Itch and Distress

Chronic pruritus (CP) is defined as an unpleasant sensation causing a desire to scratch and lasting > 6 weeks. It has a multifactorial etiology but is more frequently associated with chronic inflammatory dermatoses and systemic disorders. Psychogenic pruritus and neurological disorders are other less common etiologies, while, in some patients, it is idiopathic. CP appears to be processed by non-histaminergic pathway, contributing to its complexity and therapeutic challenge. Moreover, regardless of the etiology, it is multidimensional, including cognitive, motivational and affective components. There is a close link between psychological distress and pruritus, with particular clinical expression in chronic inflammatory dermatoses, involving the activation of the hypothalamic-pituitary-adrenal axis (and its cutaneous equivalent), the sympathetic nervous system, the release of hormones and peptides, the role of immune cells (T and B cells, macrophages) and immune-related cells in the skin (mast cells, dendritic cells and keratinocytes). Moreover, there is strong evidence that psychological factors influence the experience of pruritus. CP can also cause psychiatric disorders, including but not limited to anxiety and depression, and also lead to significant quality of life (QoL) impairment. Thereby, although a psychodermatological assessment should ideally be carried out in the context of a specific psychodermatology consultation, a brief mental health assessment could be part of the general dermatological approach to these patients. Considering that mental health, QoL and pruritus are closely linked, psychotherapeutic interventions and/or psychotropic drugs should thus be considered in some patients as an adjunct to the pharmacological treatment of CP.

Classification of psychodermatological disorders: Proposal of a new international classification

INTRODUCTION

Several classifications of psychodermatology disorders have been proposed, with most of them based on two to four main disorder category groups. However, there is, to date, no classification that has resulted from a consensus established by psychodermatology experts. The DSM-5-TR (Diagnostic and statistical manual of mental disorders (5th ed.), Text Revision) and the ICD-11 (International classification of diseases (11th revision)) also do not provide a systematized approach of psychodermatology disorders. Taking into consideration that classifications are a key pillar for a comprehensive approach to the pathologies of each branch of medicine, the proposal of a classification in psychodermatology appeared as a central need for the recognition of psychodermatological disorders, in an attempt to improve their recognition and, in that sense, to find a common language for the development of this subspecialty that crosses dermatology and psychiatry.

METHODS

Previously published classifications in psychodermatology were critically reviewed and discussed by expert opinion from an international multidisciplinary panel of 16 experts in psychodermatology and a new classification system is proposed, considering classical concepts in general dermatology and psychopathology.

RESULTS

Two main categories of disorders are presented (a main group related to primary mental health disorders and another main group related to primary skin disorders), which are subsequently subdivided into subgroups considering pathophysiological and phenomenological similarities, including key aspects of dermatological examination, namely the presence of visible skin lesions (primary and secondary skin lesions) and psychopathological correlates.

CONCLUSION

This new classification aims to unify previous classifications, systematize the disorders that belong to psychodermatology and highlight their tenuous boundaries, to improve their management. It has been built and approved by the Psychodermatology Task Force of the European Academy of Dermatology and Venereology (EADV), the European Society for Dermatology and Psychiatry (ESDaP) and the Association for Psychoneurocutaneous Medicine of North America (APMNA).

Aetiology, pathogenesis and management of neuropathic itch: A narrative review with recent updates

Neuropathic itch is a relatively common yet under-reported cause of systemic pruritus. It is a debilitating condition often associated with pain, which impairs the patient's quality of life. Although much literature exists about renal and hepatic pruritus, there is a dearth of information and awareness about neuropathic itch. The pathogenesis of neuropathic itch is complex and can result from an insult at any point along the itch pathway, ranging from the peripheral receptors and nerves until the brain. There are several causes of neuropathic itch, many of which do not produce any skin lesions and are thus, often missed. A detailed history and clinical examination are necessary for the diagnosis, while laboratory and radiologic investigations may be needed in select cases. Several therapeutic strategies currently exist involving both non-pharmacological and pharmacological measures, the latter including topical, systemic, and invasive options. Further research is ongoing to clarify its pathogenesis and to design newer targeted therapies with minimal adverse effects. This narrative review highlights the current understanding of this condition, focusing on its causes, pathogenesis, diagnosis, and management, along with newer investigational drugs.

Personality Characteristics, Anxiety Sensitivity, Anxiety, and Depression Levels on Patients Diagnosed with Psychogenic Pruritus

BACKGROUND

This study aimed to investigate the personality traits, anxiety sensitivity (AS), anxiety, and depression levels in patients diagnosed with psychogenic pruritus (PP). Certain personality traits may come to the fore in psychosomatic disorders; these traits are thought to make the person vulnerable to psychosomatic diseases. This study aimed to investigate the personality traits, anxiety sensitivity (AS), anxiety, and depression levels in patients diagnosed with psychogenic pruritus (PP).

METHODS

Thirty-seven patients diagnosed with PP (patient group) and 21 healthy controls were included in the study. Sociodemographic Data Form, Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Anxiety Sensitivity Index-3 (ASI-3), and Eysenck Personality Questionnaire (EPQ) were administered to all participants.

RESULTS

Patients' EPQ scores for the extraversion, neuroticism, psychoticism, and lie subdimensions and EPQ-total scores were significantly higher than those of the control group (P = .001; P < .001; P < .001; P = .008; P < .001, respectively). The total score of ASI-3 scale and the scores of all subdimensions (physical, cognitive, and social) were significantly higher in patients than in controls (P < .001). The BAI (26.8 ± 9.3) and BDI (24.2 ± 8.6) total scores of the patients were significantly higher than those of the control group (P < .001).

CONCLUSIONS

According to EPQ, patients diagnosed with PP are extroverted, but also cold, distrustful, and aloof; show impulsive behavior; are anxious, depressed, and nervous; overly emotional; and prone to lying. Patients suffer more from anxiety, depressive symptoms, and AS in physical, cognitive, and social subdimensions than healthy people. Our findings highlight the importance of psychiatric assessment in PP patients. In this context, we believe that PP deserves to be studied in a broad spectrum with its cognitive, behavioral, and social aspects.

Regenerative medicine for neuropathic pain: physiology, ultrasound and therapies with a focus on alpha-2-macroglobulin

The currently available drugs to treat neuropathic pain do not provide adequate pain management. As such, other treatments including stem cells, platelet-rich plasma and plasma-derived molecules such as alpha-2 macroglobulin (A2M) are being explored because they show promising potential for neuropathic pain. The various mechanisms and immunomodulatory effects could be a desirable approach in targeting neuropathic pain. This review indicates that A2M can be highly efficacious due to its conformational change during activation and specificity of action on various cytokines. Its ability to reduce neuropathic pain can further the future of neuropathic intervention. However, there is a lack of robust clinical studies and thus further research is needed to verify and expand the understanding of its therapeutic effects.

Circuit Mechanisms of Itch in the Brain

Itch is an unpleasant somatic sensation with the desire to scratch, and it consists of sensory, affective, and motivational components. Acute itch serves as a critical protective mechanism because an itch-evoked scratching response will help to remove harmful substances invading the skin. Recently, exciting progress has been made in deciphering the mechanisms of itch at both the peripheral nervous system and the CNS levels. Key neuronal subtypes and circuits have been revealed for ascending transmission and the descending modulation of itch. In this review, we mainly summarize the current understanding of the central circuit mechanisms of itch in the brain.