Itching as a systemic disease

Pruritus Severity and Serum Phosphate in CKD: A Post Hoc Analysis of Difelikefalin Studies

Key Points

No correlation was observed between pruritus severity and serum phosphate or response to placebo or difelikefalin in patients with CKD-associated pruritus undergoing hemodialysis. Difelikefalin improved itch versus placebo irrespective of baseline serum phosphate.

Background

CKD-associated pruritus (CKD-aP) has historically been associated with elevated serum phosphate (sP). Difelikefalin is a novel antipruritic agent approved for the treatment of moderate-to-severe CKD-aP in adults undergoing hemodialysis. This post hoc analysis used data from phase 3 difelikefalin studies (KALM-1, KALM-2, and open-label Study 3105) to assess the role of sP in the pathogenesis of CKD-aP and whether difelikefalin ameliorates CKD-aP in patients with and without elevated sP.

Methods

Patients with moderate-to-severe CKD-aP undergoing hemodialysis with baseline sP data were included in the analysis (KALM-1 and KALM-2, n =845; Study 3105, n =220). Assessments included correlation between 24-hour Worst Itching Intensity Numerical Rating Scale (WI-NRS) score and sP.

Results

In KALM-1 and KALM-2, baseline characteristics in the overall population were similar between patients with sP ≤5.5 and >5.5 mg/dl; no significant correlation was observed between WI-NRS and sP at baseline or in week 12. In patients receiving placebo, no correlation was observed between WI-NRS and sP at baseline or between their change from baseline to week 12 (all P < 0.05). Clinically meaningful (≥3-point) reductions from baseline to week 12 in WI-NRS scores were reported by more patients receiving placebo with baseline sP ≤5.5 mg/dl than >5.5 mg/dl (least squares mean 37.2% versus 27.4%; odds ratio [95% confidence interval], 0.63 [0.41 to 0.97]; P = 0.04). A greater proportion of patients treated with difelikefalin achieved a ≥3-point WI-NRS reduction from baseline to week 12 versus placebo and was similar between sP ≤5.5 and >5.5 mg/dl subgroups (least squares means 51.1% versus 57.6% [P = 0.20]). No significant relationships between sP and WI-NRS in patients receiving difelikefalin were identified in Study 3105 at any time point.

Conclusions

No correlation was observed between pruritus severity and sP or response to placebo or difelikefalin in patients with CKD-aP undergoing hemodialysis. Difelikefalin improved itch versus placebo irrespective of baseline sP.

The JAK1/JAK2 inhibitor ruxolitinib inhibits mediator release from human basophils and mast cells

Introduction

The Janus kinase (JAK) family includes four cytoplasmic tyrosine kinases (JAK1, JAK2, JAK3, and TYK2) constitutively bound to several cytokine receptors. JAKs phosphorylate downstream signal transducers and activators of transcription (STAT). JAK-STAT5 pathways play a critical role in basophil and mast cell activation. Previous studies have demonstrated that inhibitors of JAK-STAT pathway blocked the activation of mast cells and basophils.

Methods

In this study, we investigated the in vitro effects of ruxolitinib, a JAK1/2 inhibitor, on IgE- and IL-3-mediated release of mediators from human basophils, as well as substance P-induced mediator release from skin mast cells (HSMCs).

Results

Ruxolitinib concentration-dependently inhibited IgE-mediated release of preformed (histamine) and de novo synthesized mediators (leukotriene C4) from human basophils. Ruxolitinib also inhibited anti-IgE- and IL-3-mediated cytokine (IL-4 and IL-13) release from basophils, as well as the secretion of preformed mediators (histamine, tryptase, and chymase) from substance P-activated HSMCs.

Discussion

These results indicate that ruxolitinib, inhibiting the release of several mediators from human basophils and mast cells, is a potential candidate for the treatment of inflammatory disorders.

Characterization of cells and mediators associated with pruritus in primary cutaneous T-cell lymphomas

Patients with primary cutaneous T-cell lymphoma (CTCL) often experience severe and difficult-to-treat pruritus that negatively affects their quality of life (QoL). However, the mechanisms of pruritus in CTCL, including mycosis fungoides (MF), remain largely unknown, and detailed characteristics of CTCL-associated pruritus is not fully elucidated. To characterize pruritus in CTCL, cutaneous B-cell lymphoma (CBCL), and large plaque parapsoriasis (LPP), and to identify potential itch mediators involved in the pathogenesis of pruritus in CTCL patients. Clinical data and blood samples were collected from 129 healthy subjects and 142 patients. Itch intensity, QoL impairment, psychological distress, and sleep quality were assessed using validated questionnaires and instruments. Blood levels of BDNF, CCL24, GRP, IL-31, IL-33, sST2, substance P, TSLP, tryptase and total IgE were measured using ELISA or ImmunoCAP. Pruritus was prevalent in CTCL, LPP and CBCL patients, with higher prevalence and severity observed in CTCL. In CTCL, pruritus correlated with significant impairment in QoL, sleep, psychological distress. Compared to healthy controls, elevated levels of IL-31, IL-33, substance P, total IgE, tryptase, and TSLP were found in MF patients. A comparison of MF patients with and without pruritus revealed higher levels of IL-31, substance P, GRP, and CCL24 in the former. Itch intensity positively correlated with IL-31, GRP, CCL24, and tryptase levels. Pruritus significantly burdens CTCL patients, necessitating appropriate therapeutic management. Our findings suggest that various non-histaminergic mediators such as tryptase and IL-31 could be explored as novel therapeutic targets for managing pruritus in MF patients.

Beyond the classic players: Mas-related G protein-coupled receptor member X2 role in pruritus and skin diseases

Chronic spontaneous urticaria (CSU), atopic dermatitis (AD), psoriasis and rosacea are highly prevalent inflammatory skin conditions which impose a significant burden on patients' quality of life. Their pathophysiology is likely multifactorial, involving genetic, immune and environmental factors. Recent advancements in the field have demonstrated the key role of mast cells (MC) in the pathophysiology of these conditions. The Mas-related G protein-coupled receptor X2 (MRGPRX2) has emerged as a promising non-IgE-mediated MC activation receptor. MRGPRX2 is predominately expressed on MC and activated by endogenous and exogenous ligands, leading to MC degranulation and release of various pro-inflammatory mediators. Mounting evidence on the presence of endogenous MRGPRX2 agonists (substance P, cortistatin-14, LL37, PAMP-12 and VIP) and its high expression among patients with CSU, AD, rosacea, psoriasis and chronic pruritus emphasizes the pathogenic role of MRGPRX2 in these conditions. Despite the currently available treatments, there remains a pressing need for novel drug targets and treatment options for these chronic inflammatory skin conditions. Here, we reviewed the pathogenic role of MRGPRX2 and its potential as a novel therapeutic target and provided an update on future research directions.

Managing Pruritus in Advanced Chronic Disease

Even though pruritus affects a significant number of people with chronic disease, it is rarely adequately treated. Drug therapies often rely on antihistamines, which have not shown to be beneficial in systemic pruritus. Hydroxyzine is frequently used to treat pruritus associated with kidney failure. Since Canada's sole manufacturer of hydroxyzine is no longer making this product, this is an ideal time to review the mechanisms of itch in advanced organ failure and the specific therapies that give relief. Although there is literature describing itch in patients with cancer, this article is limited to pathogenesis and treatment of systemic itch secondary to chronic, noncancer diseases. We summarize recent systematic reviews, although the studies included in these reviews are often small, and mostly cohort studies.

Intravenous difelikefalin for the treatment of hemodialysis pruritus

INTRODUCTION

Patients with chronic kidney disease (CKD) undergoing hemodialysis often experience significant itch secondary to their condition and a subsequent reduction in their overall quality of life. Current treatments are underwhelming, necessitating the search for new, effective therapeutic options to combat itch in this population.

AREAS COVERED

The purpose of this review is to explore the available data for the use of intravenous difelikefalin in patients with CKD undergoing hemodialysis. The pathophysiology of CKD-associated itch is multifactorial, with one proposed mechanism involving an imbalance in the endogenous opioid system, favoring upregulation of itch-activating μ-opioid receptors (MORs) and downregulation of itch-inhibiting κ-opioid receptors (KORs). Dysregulation of the immune system is also involved. Difelikefalin is a recent FDA approved treatment that functions as peripherally acting KOR agonist, targeting this imbalance in the endogenous opioid system seen in CKD patients with itch and having an anti-inflammatory effect on immune cells. Clinical data on intravenous difelikefalin is promising regarding its ability to reduce itch in CKD patients on hemodialysis and improve patient quality of life, with few, mild adverse side effects.

EXPERT OPINION

As intravenous difelikefalin becomes more widely used in the clinical setting, further studies assessing long-term efficacy and safety will be needed.

Immune Homeostasis: A Novel Example of Teamwork

All living organisms must maintain homeostasis to survive, reproduce, and pass their traits on to the next generation. If homeostasis is not maintained, it can result in various diseases and ultimately lead to death. Physiologists have coined the term "homeostasis" to describe this process. With the emergence of immunology as a separate branch of medicine, the concept of immune homeostasis has been introduced. Maintaining immune homeostasis is crucial to support overall homeostasis through different immunological and non-immunological routes. Any changes in the immune system can lead to chronic inflammatory or autoimmune diseases, immunodeficiency diseases, frequent infections, and cancers. Ongoing scientific advances are exploring new avenues in immunology and immune homeostasis maintenance. This chapter introduces the concept of immune homeostasis and its maintenance through different mechanisms.

Chronic Kidney Disease-Associated Pruritus, Still a Vexing Problem

Chronic kidney disease-associated pruritus (CKD-aP), formerly termed uremic pruritus, is a severely distressing condition that is common (60% of patients on dialysis) and frequently underdiagnosed and untreated.1,2 The pruritus can be severe enough to diminish sleep and is associated with worse mortality rates, as demonstrated in several large studies.1,2 It can also occur in nondialysis patients with stage 3 to 5 CKD, with an increasing prevalence in patients with worsening kidney function, age, and medical comorbidities. The pathophysiology likely involves many factors and molecules.3.

Itch: from the skin to the brain - peripheral and central neural sensitization in chronic itch

Similar to chronic pain, chronic itch is frequently linked to neural sensitization, a phenomenon wherein the nervous system becomes hypersensitive to stimuli. This process of neural sensitization of chronic itch is orchestrated by various signaling pathways and mediators in both the peripheral and central nervous systems. At the level of the peripheral nervous system, inflammation and neuroimmune interactions induce plastic changes to peripheral nerve fibers, thereby amplifying the transmission of itch signaling. Neural sensitization in the central nervous system occurs at both the spinal cord and brain levels. At the level of the spinal cord, it involves hyperactivity of itch-activating spinal pathways, dysfunction of spinal inhibitory circuits, and attenuation of descending supraspinal inhibitory pathways. In the brain, neural sensitization manifests as structural and functional changes to itch-associated brain areas and networks. Currently, we have a diverse array of neuroimmune-modulating therapies targeting itch neural sensitization mechanisms to help with providing relief to patients with chronic itch. Itch research is a dynamic and continually evolving field, and as we grow in our understanding of chronic itch mechanisms, so will our therapeutic toolbox. Further studies exploring the peripheral and central neural sensitization mechanisms in the context of chronic itch are needed.

Pruritus in keloid scars: mechanisms and treatments

Keloids occur after cutaneous injury and can cause distress due to physical appearance and associated symptoms such as pain and pruritus. Keloid-associated pruritus is a common manifestation and has negative impacts on quality of life. The mechanism underlying this type of pruritus is multifactorial and thought to involve small nerve fiber damage, neurogenic inflammation, and a Th2-predominant inflammatory response. Various agents have been shown to reduce keloid pruritus, including intralesional corticosteroids, botulinum toxin A, 5-fluorouracil, and bleomycin. Other treatment modalities such as cryotherapy and hyperbaric oxygen therapy are also effective. Future treatments targeting the mechanisms involved in keloid-associated itch could provide improvements in pruritus and quality of life in these patients, but further studies on the efficacy of these agents are needed.

Chronic kidney disease-associated pruritus (CKD-aP) is associated with worse quality of life and increased healthcare utilization among dialysis patients

PURPOSE

Chronic pruritus significantly impairs hemodialysis patients' health status and quality of life (QOL) and it is associated with higher mortality rate, more frequent hospitalizations, poorer dialysis and medication adherence, and deteriorated mental status. However, pruritus is still underestimated, underdiagnosed, and undertreated in the real-life clinical scenario. We investigated prevalence, clinical characteristics, clinical correlates, severity as well as physical and psychological burden of chronic pruritus among adult hemodialysis patients in a large international real-world cohort.

METHODS

We conducted a retrospective cross-sectional study of patients registered in 152 Fresenius Medical Care (FMC) NephroCare clinics located in Italy, France, Ireland, United Kingdom, and Spain. Demographic and medical data were retrieved from the EuCliD® (European Clinical) database, while information on pruritus and QoL were abstracted from KDQOL™-36 and 5-D Itch questionnaire scores.

RESULTS

A total of 6221 patients were included, of which 1238 were from France, 163 Ireland, 1469 Italy, 2633 Spain, and 718 UK. The prevalence of mild-to-severe pruritus was 47.9% (n = 2977 patients). Increased pruritus severity was associated with increased use of antidepressants, antihistamines, and gabapentin. Patients with severe pruritus more likely suffered from diabetes, more frequently missed dialysis sessions, and underwent more hospitalizations due to infections. Both mental and physical QOL scores were progressively lower as the severity of pruritus increased; this association was robust to adjustment for potential confounders.

CONCLUSION

This international real-world analysis confirms that chronic pruritus is a highly prevalent condition among dialysis patients and highlights its considerable burden on several dimensions of patients' life.

Angelica Yinzi Alleviates Pruritus-Related Atopic Dermatitis through Skin Repair, Antioxidation, and Balancing Peripheral μ- and κ-opioid Receptors

Background

Angelica Yinzi (AYZ) is a Chinese traditional herbal formula reported to attenuate itches and inflammation caused by atopic dermatitis (AD). However, the underlying mechanism of AYZ in the attenuation of itchiness and inflammation remains unknown.

Objective

This study investigated the mechanism of AYZ in reducing itchiness in mice with 1-chloro-2,4-dinitrobenzene- (DNCB-)-induced atopic dermatitis.

Methods

Hematoxylin and eosin (H&E) and toluidine blue staining were used to evaluate pathological changes in skin tissue, while an enzyme-linked immunosorbent assay (ELISA) was used to assess the cytokine levels in the skin. After that, qRT-PCR was performed to determine the mRNA levels of cytokines in the skin. Immunofluorescence and western blotting analysis were further used to assess µ-opioid receptor (MOR) expression and immunohistochemistry to assess the p-ERK, p-AKT, and κ-opioid receptor (KOR).

Results

The AYZ treatment alleviated the AD clinical symptoms, including decreasing the scratching frequency, the ear thickness, and the infiltration of mast cells, lymphocytes, inflammatory cells, and mononuclear cells. In addition, AYZ inhibited the expression of interleukin (IL)-13, thymic stromal lymphopoietin (TSLP), and reduced neuraminidase (NA), corticotropin-releasing factor (CRF), and reactive oxygen species (ROS) expression. Markers involved in itches, such as p-ERK and p-AKT, were significantly downregulated following AYZ treatment. Besides, AYZ significantly increased MOR expression and downregulated KOR in the epidermis and spinal cord.

Conclusion

Our findings imply that AYZ ameliorates pruritus-related AD through skin repair, antioxidation, and balancing peripheral MOR and KOR. The findings in this study lay a theoretical foundation for the control mechanism of peripheral itch.

Atopic dermatitis and chronic kidney disease: a bidirectional Mendelian randomization study

Background

A bidirectional association between atopic dermatitis and chronic kidney disease (CKD) has been revealed in observational studies, whereas the causality of this association was unclear. We conducted a Mendelian randomization study to determine the bidirectional causal association between atopic dermatitis and CKD.

Methods

Independent genetic instruments associated with atopic dermatitis and CKD at the genome-wide significance level were chosen from corresponding meta-analyses of genome-wide association studies. Summary-level data for atopic dermatitis were obtained from the EAGLE Eczema consortium (30,047 cases and 40,835 controls) and FinnGen consortium (7,024 cases and 198,740 controls). Summary-level data for CKD were derived from CKDGen consortium (64,164 cases and 625,219 controls) and FinnGen consortium (3,902 cases and 212,841 controls). The inverse-variance weighted method was used in the main analysis and supplemented with three sensitivity analyses.

Results

Genetic predisposition to atopic dermatitis was associated with an increased risk of CKD. For a one-unit increase in the prevalence of atopic dermatitis, the odds ratio of CKD was 1.07 (95% confidence interval: 1.01-1.12). In the reverse Mendelian randomization analysis, the odds ratio of atopic dermatitis was 1.14 (95% confidence interval: 1.03-1.26) for a one-unit increase in the prevalence of CKD. The associations persisted in sensitivity analyses and no pleiotropy was detected.

Conclusion

This Mendelian randomization study suggests a bidirectional positive association between atopic dermatitis and CKD.

miRNA-203b-3p Induces Acute and Chronic Pruritus through 5-HTR2B and TRPV4

Growing evidence indicates that transient receptor potential (TRP) channels contribute to different forms of pruritus. However, the endogenous mediators that cause itch through transient receptor potential channels signaling are poorly understood. In this study, we show that genetic deletion or pharmacological antagonism of TRPV4 attenuated itch in a mouse model of psoriasis induced by topical application of imiquimod. Human psoriatic lesions showed increased expression of several microRNAs, including the miR-203b-3p, which induced a calcium ion response in rodent dorsal root ganglion neurons and scratching behavior in mice through 5-HTR2B activation and the protein kinase C‒dependent phosphorylation of TRPV4. Computer simulation revealed that the miR-203b-3p core sequence (GUUAAGAA) that causes 5-HTR2B/TRPV4-dependent itch targets the extracellular side of 5-HTR2B by interacting with a portion of the receptor pocket consistent with its activation. Overall, we reveal the unconventional pathophysiological role of an extracellular microRNA that can behave as an itch promoter through 5-HTR2B and TRPV4.

Role of kappa-opioid and mu-opioid receptors in pruritus: Peripheral and central itch circuits

Modern genetic approaches in animal models have unveiled novel itch-specific neural pathways, emboldening a paradigm in which drugs can be developed to selectively and potently target itch in a variety of chronic pruritic conditions. In recent years, kappa-opioid receptors (KORs) and mu-opioid receptors (MORs) have been implicated in both the suppression and promotion of itch, respectively, by acting on both the peripheral and central nervous systems. The precise mechanisms by which agents that modulate these pathways alleviate itch remains an active area of investigation. Notwithstanding this, a number of agents have demonstrated efficacy in clinical trials that influence both KOR and MOR signalling. Herein, we summarize a number of opioid receptor modulators in development and their promising efficacy across a number of chronic pruritic conditions, such as atopic dermatitis, uremic pruritus and beyond.

How Does Botulinum Toxin Inhibit Itch?

Two decades after reports of the anti-pruritic effects of botulinum neurotoxins (BoNTs), there is still no approved product for the anti-itch indication of BoNTs, and most clinical case reports still focus on the off-label use of BoNTs for various itchy conditions. Few randomized clinical trials have been conducted with controversial results, and the beneficial effects of BoNTs against itch are mainly based on case studies and case series. These studies are valuable in presenting the potential application of BoNTs in chronic pruritic conditions, but due to the nature of these studies, they are categorized as providing lower levels of evidence or lower grades of recommendation. To obtain approval for the anti-pruritic indication of BoNTs, higher levels of evidence are required, which can be achieved through conducting large-scale and well-designed studies with proper control groups and established careful and reliable primary and secondary outcomes. In addition to clinical evidence, presenting the mechanism-based antipruritic action of BoNTs can potentially strengthen, accelerate, and facilitate the current efforts towards further investments in accelerating the field towards the potential approval of BoNTs for itchy conditions. This review, therefore, aimed to provide the state-of-the-art mechanisms underlying the anti-itch effect of BoNTs from basic studies that resemble various clinical conditions with itch as a hallmark. Evidence of the neuronal, glial, and immune modulatory actions of BoNTs in reducing the transmission of itch are presented, and future potential directions are outlined.

Difelikefalin in the Treatment of Chronic Kidney Disease-Associated Pruritus: A Systematic Review

Chronic kidney disease-associated pruritus (CKD-aP) is a chronic condition that significantly reduces the quality of life of patients with end-stage renal disease. The etiology is not fully understood, but imbalance in the activity of the opioid pathways, including downregulation of the kappa-opioid receptor, may contribute to itching sensation. Difelikefalin is a selective, peripherally acting kappa-opioid receptor (KOR) agonist. Recently, difelikefalin has been approved as a first drug for the treatment of pruritus associated with chronic kidney disease (CKD) in adult hemodialysis patients. A systematic review of currently available clinical trials was performed to assess the efficacy and safety of difelikefalin in patients with uremic pruritus. A literature review was conducted in May 2022 based on the PRISMA 2020 guidelines. The analyzed clinical trials showed that difelikefalin was effective in reducing pruritus in patients as assessed by the Worst Itching Intensity Numerical Rating Scale. Improvement in quality of life assessed on the basis of the Skindex score and the 5-D itch scale was also noticed. The most commonly reported side effects were mild and included nausea, vomiting, dizziness, and diarrhea. Due to its proven efficacy and good safety profile, difelikefalin is a promising drug for the treatment of pruritus in patients with chronic kidney disease.

Cholestatic Itch: Our Current Understanding of Pathophysiology and Treatments

Hepatic pruritus is common in liver conditions, including cholestasis and nonalcoholic fatty liver disease. The pruritus can be severe enough to diminish sleep and decrease quality of life. The pathophysiology likely involves many molecules and receptors, including bile acids, bilirubin, lysophosphatidic acid (LPA), endogenous opioids, and serotonin. Recent advances suggest a significant role of Mas-related G protein-coupled receptor X4 (MRGPRX4) and autotaxin/LPA as key players in cholestatic pruritus. Further research is needed to develop increasingly targeted therapies with greater efficacy, especially given that many patients report itch refractory to various treatments. Cholestyramine was the only US FDA-approved drug for cholestatic pruritus until recent approval of ileal bile acid transporter (IBAT) inhibitors for use in the pediatric cholestatic conditions, progressive familial intrahepatic cholestasis and Alagille syndrome. Both medications decrease the bile acid pool. IBAT inhibitors are under investigation for broader use, and targeting LPA receptors and MRGPR4 are additional attractive options.

Functional roles of neuromedin B and gastrin-releasing peptide in regulating itch and pain in the spinal cord of non-human primates

Despite accumulating evidence in rodents, the functional role of neuromedin B (NMB) in regulating somatosensory systems in primate spinal cord is unknown. We aimed to compare the expression patterns of NMB and its receptor (NMBR) and the behavioral effects of intrathecal (i.t.) NMB with gastrin-releasing peptide (GRP) on itch or pain in non-human primates (NHPs). We used six adult rhesus monkeys. The mRNA or protein expressions of NMB, GRP, and their receptors were evaluated by quantitative reverse transcription polymerase chain reaction, immunohistochemistry, or in situ hybridization. We determined the behavioral effects of NMB or GRP via acute thermal nociception, capsaicin-induced thermal allodynia, and itch scratching response assays. NMB expression levels were greater than those of GRP in the dorsal root ganglia and spinal dorsal horn. Conversely, NMBR expression was significantly lower than GRP receptor (GRPR). I.t. NMB elicited only mild scratching responses, whereas GRP caused robust scratching responses. GRP- and NMB-elicited scratching responses were attenuated by GRPR (RC-3095) and NMBR (PD168368) antagonists, respectively. Moreover, i.t. NMB and GRP did not induce thermal hypersensitivity and GRPR and NMBR antagonists did not affect peripherally elicited thermal allodynia. Consistently, NMBR expression was low in both itch- and pain-responsive neurons in the spinal dorsal horn. Spinal NMB-NMBR system plays a minimal functional role in the neurotransmission of itch and pain in primates. Unlike the functional significance of the GRP-GRPR system in itch, drugs targeting the spinal NMB-NMBR system may not effectively alleviate non-NMBR-mediated itch.

Prevalence and potential risk factors of chronic pruritus among community middle-aged and older population in Beijing, China

BACKGROUND

Chronic pruritus is a common problem among older adults, with a significant impact on their quality of life. However, it is under-studied epidemiologically, especially among Chinese older adults.

OBJECTIVE

To identify the prevalence and explore the risk factors of chronic pruritus among the middle-aged and older adults in Beijing, China.

METHODS

A total of 929 participants aged ≥35 years from six communities in Beijing, China, were interviewed. The survey collected the demographic characteristics, the experience of chronic pruritus (>6 weeks), chronic disease history, the level of physical activities, and sleep quality. A population-based case-control study was conducted, including 178 chronic pruritus cases and 697 controls. A multivariate logistic regression model was performed to explore the risk factors of chronic pruritus. Additionally, a random forest algorithm was used to rank the importance of potential risk factors and analyze the overall interpretation of risk factors.

RESULTS

The prevalence of chronic pruritus was 19.48% (181/929) among the Beijing middle-aged and elderly population. The findings indicated that older adults aged 65 years old or above, male, with college or higher degree, alcohol drinking, hypertension, hyperlipidemia, chronic lung disease, cardiovascular disease, digestive system disease and osteoarthritis/rheumatism, middle or low sleep quality were associated with the increased risk of chronic pruritus, respectively. Physical activity level (≥3000 Met) was associated with a decreased risk of chronic pruritus. The rank according to the most contribution of chronic pruritus risk was sleep quality, education, physical activity level, osteoarthritis/rheumatism, age, and gender.

CONCLUSION

Prevalence of chronic pruritus was high among the Chinese middle-aged and elderly population. Age, gender, high education, alcohol drinking, hypertension, hyperlipidemia, chronic lung disease, cardiovascular disease, digestive system disease, osteoarthritis /rheumatism, poor sleep quality may serve as risk factors of chronic pruritus. Moderate and high physical activity levels may serve as protective factors of chronic pruritus risk.

Clinical management of chronic kidney disease-associated pruritus: current treatment options and future approaches

Chronic kidney disease (CKD)-associated pruritus (CKD-aP) is an underdiagnosed yet severely distressing condition that impacts 60% of patients on dialysis and many nondialysis patients with Stages 3–5 CKD. However, despite its high prevalence, there are currently limited treatment options available for these patients and a lack of treatment guidelines for clinicians. In this manuscript, we reviewed the available literature in order to evaluate the current management and treatment options for CKD-aP, including dialysis management, topical treatments, gabapentinoids, opioids and alternative medicine. We also review the available data on CKD-aP treatments in development and propose new guidelines for managing patients with CKD-aP.

Advances in Atopic Dermatitis in 2019-2020: Endotypes from skin barrier, ethnicity, properties of antigen, cytokine profiles, microbiome, and engagement of immune cells

Key research advances in atopic dermatitis (AD) suggest the complexity of its endotypes. A comprehensive serum biomarker panel revealed at least four types of AD. Some represent classic TH2-dominant AD with filaggrin mutations commonly reported in Europeans, a simultaneously activated multipolar axes of cytokines often reported in Asians, and an intrinsic type characterized by TH2-inferiority. Innate lymphoid cells, including NK cells, NKT cells, and fibroblasts, play a role in AD development and heterogeneity. Here, we discuss the endotypes of AD from the perspective of antigen types (hapten vs. protein antigens), barrier function, and a novel set of immune cells. Endotypic stratification of AD may lead to the development of customized therapeutic strategies in the future.

Systemic causes of non-dermatologic chronic pruritus in the pediatric population and their management: An unexplored area

Chronic pruritus associated with systemic diseases in the pediatric population has been infrequently addressed in the literature. This review focuses on chronic pruritus presenting without cutaneous manifestations. Common systemic etiologies include diseases with hepatic, renal, and hematologic origins. This encompasses several congenital liver disorders, end-stage renal disease (ESRD), and lymphoproliferative disorders such as Hodgkin's lymphoma. In this paper, an expert panel describes the clinical characteristics, pathophysiology, and therapeutic treatment ladders for chronic pruritus associated with the aforementioned systemic etiologies. Novel therapies are also reviewed. Our aim is to shed light on this unexplored area of pediatric dermatology and instigate further research.

Approach to the Patient with Chronic Pruritus

Chronic pruritus (itch lasting ≥6 weeks) is a bothersome chief complaint that may present in a broad variety of diseases. Most itch-causing diagnoses fit into 1 of 5 categories (inflammatory, secondary to systemic disease, neuropathic, chronic pruritus of undetermined origin, and psychogenic itch) and this broad differential can be narrowed using key findings in the history and physical. In this article, we discuss which key findings are most pertinent for narrowing this differential and guiding further workup and treatment, as well as how to treat many itchy conditions.

The pruritogenic role of the type 2 immune response in diseases associated with chronic itch

While there is a vast array of aetiologies that may lead to chronic pruritus, recent data suggests that many of these conditions share similar interactions between keratinocytes, nerves, and the immune system. Specifically, the type 2 immune response, including Th2 T Cells and their related cytokines, has been noted to play a major role in the development of pruritus in a variety of itchy conditions. To date, atopic dermatitis is the most striking example of this pathogenesis. However, the body of literature supporting its role in many other itchy conditions, including other inflammatory, bullous, as well as systemic diseases, continues to grow. In addition, new treatments targeting this type 2 immune system continue to be developed and investigated. In the current review, we present the current body of literature supporting the role of the type 2 immune response in itchy conditions beyond atopic dermatitis as well as potential therapeutic options that target this pathway for chronic itch.

Periostin, an Emerging Player in Itch Sensation

Periostin, an extracellular matrix and matricellular protein, binds to several types of integrins that transduce its signals. Its function in allergic inflammation is the establishment of sustained chronic inflammation through an amplification of T helper type 2‒immune responses. In addition, recent studies have shown a significant role of periostin in itch sensation through direct integrin-mediated stimulation of nerve fibers and interaction with immune and nonimmune cells (e.g., macrophages, eosinophils, basophils, and keratinocytes). The objective of this review is to describe the role of periostin in itch induction in human and animal models and its expression in human pruritic conditions.

Use of Butorphanol as Treatment for Cholestatic Itch

BACKGROUND

Pruritus is a debilitating symptom of cholestatic diseases such as primary biliary cholangitis and primary sclerosing cholangitis and often results in major reduction in quality of life for afflicted patients. Classic treatment options for the treatment of cholestatic pruritus include antihistamines, bile acid resins, serotonin reuptake inhibitors, and mu-opioid antagonists. Unfortunately, these drugs are not always successful in treating pruritus of cholestasis and may be associated with adverse effects. Recent advances in our understanding of itch pathophysiology have led to the use of butorphanol, a kappa-opioid agonist and mu-opioid antagonist, for the treatment of various forms of pruritus. Reports of butorphanol to treat cholestatic itch specifically are rare.

AIMS

To better understand the role of butorphanol in the treatment of cholestatic pruritus, including characterization of its side effect profile.

METHODS

We present a case series of eight adult patients with cholestatic disease who were treated with butorphanol in hopes of alleviating intractable pruritus. Patients were identified through a clinical data request form serviced by University of Miami Information Technology.

RESULTS

Five out of eight patients (62.5%) reported successful reductions in itch severity after treatment with butorphanol, two patients reported no (or transient) change in itch severity, and one patient reported a paradoxical increase in itching. Side effects included somnolence, sedation, nausea, vomiting, and dizziness.

CONCLUSIONS

Butorphanol was safe and leads to clinically significant symptomatic improvement. Clinicians should be aware of butorphanol as an off-label treatment option for pruritus of cholestasis. Further studies are needed to better characterize the effect of butorphanol on cholestatic itch.

Safety considerations for the management of cholestatic itch

Introduction: Pruritus is adisabling symptom common to cholestatic liver disorders. Its pathophysiology has not been completely elucidated and although multiple mediators have been identified, only lysophosphatidic acid (LPA) and its synthetizing enzyme autotaxin (ATX) appear to consistently correlate with symptom intensity. This review aims to summarize the most relevant safety and efficacy data regarding both standard and new medications utilized to treat pruritus in cholestatic liver disease.Areas covered: International societies like the AASLD and EASL recommend astepwise approach for the management of cholestatic itch. However, therapeutic response is variable. Cholestyramine is considered first-line, followed by rifampicin, naltrexone and sertraline. When used appropriately, these medications have afavorable adverse events profile with most side effects related to drug class and not to the underlying etiology of liver disease.Expert opinion: Although conventional therapies seem to be effective in aproportion of patients, asizable number of cases remain refractory and require the utilization of experimental treatments. Multiple potential targets, especially in the ATX-LPA axis have yet to be pharmacologically explored, with ongoing translational and clinical research. Novel drugs are currently being developed for the management of cholestatic itching with promising results and afavorable safety profile.

Pediatric diabetes and skin disease (PeDiSkin): A cross-sectional study in 369 children, adolescents and young adults with type 1 diabetes

BACKGROUND

The spectrum of skin disorders in children with type 1 diabetes (T1D) and their impact on affected persons are still incompletely understood. This study assessed the prevalence of skin diseases, cutaneous complications associated with T1D treatment and skin-related quality of life (QoL) in young T1D persons.

METHODS

Participation in this interdisciplinary, single-center, cross-sectional, observational study was offered to all persons with T1D ≤20 years. Participants were characterized by a detailed medical history, routine laboratory workup, thorough clinical examinations and an established QoL questionnaire.

RESULTS

Three hundred and sixty-nine persons were recruited (55% male; age 12.3 ± 4.4 years; HbA1c 7.4 ± 1.0%; mean ± SD). Continuous subcutaneous insulin infusion (CSII) was used by 72.4%, multiple daily injections (MDI) by 27.6% and continuous glucose monitoring (CGM) by 76%. Skin affections occurred in 91.8% of the study population. Device-associated lesions were most prevalent, including lipohypertrophy in 42.2% of MDI and 46.8% of CGM users and contact eczema associated with CSII or CGM in 14.2% and 18.3%, respectively. Diabetes-associated skin disorders and skin infections were rare or absent. Skin-related QoL impairment was low or absent in 95% of patients.

CONCLUSIONS

Skin diseases have a high prevalence and a broad spectrum in young persons with T1D. Eczematous reactions to CSII and CGM devices represent the most frequent skin complications. This highlights the need for regular skin checkups as an integral part of pediatric diabetes consultations and interdisciplinary cooperation for classification and treatment options.

Emerging drugs for the treatment of chronic pruritic diseases

INTRODUCTION

Chronic pruritus is non-histaminergic and mediated through a complex interplay of peripheral and central immune and neural pathways. Significant developments in the understanding of chronic pruritus have emerged and paved the way for new, emerging therapies.

AREAS COVERED

This review details the emerging drug landscape for chronic pruritus treatment, focusing on monoclonal antibody agents that target key cytokines and their receptors as well as small molecule agents that inhibit mediators of the immune and neural pathways. The article provides background regarding the currently available therapies and the rationale for the development of new agents based on the current market and recent scientific developments.

EXPERT OPINION

Identification of new targets along neuroimmune itch pathways has allowed for the development of targeted drugs which can be utilized for effective therapy. As we enter a new era of chronic itch treatments, we face exciting prospects and challenges.

Interleukin-31 and Chronic Pruritus of Unknown Origin

Chronic pruritus of unknown origin (CPUO) is a refractory condition. The expression of Interleukin-31 (IL-31), a major pruritogenic cytokine, in CPUO patients has not been investigated. This study aimed to investigate the potential association of IL-31 with CPUO. This was a cross-sectional, analytical study. Patients diagnosed with CPUO and healthy subjects were included at a ratio of 1:2. Serum IL-31 levels were measured in both groups and compared. There were 10 CPUO and 20 healthy subjects who participated in this study. The median IL-31 level in the CPUO group was significantly higher than in the healthy group (127.3 vs 34.4 pg/mL; P < .001). The presence of CPUO was independently associated with IL-31 levels with a coefficient of 89.678 (P < .001). The serum IL-31 cutoff point for CPUO was 56.8 pg/mL, with an area under the receiver operating characteristic curve (ROC) of 100%. Chronic pruritus of unknown origin was significantly and independently associated with higher IL-31 levels. Further clinical trials of IL-31-related treatment may be justified in CPUO patients.

Outside-in hypothesis revisited: The role of microbial, epithelial, and immune interactions

OBJECTIVE

Our understanding of the origin of allergic diseases has increased in recent years, highlighting the importance of microbial dysbiosis and epithelial barrier dysfunction in affected tissues. Exploring the microbial-epithelial-immune crosstalk underlying the mechanisms of allergic diseases will allow the development of novel prevention and treatment strategies for allergic diseases.

DATA SOURCES

This review summarizes the recent advances in microbial, epithelial, and immune interactions in atopic dermatitis, allergic rhinitis, chronic rhinosinusitis, and asthma.

STUDY SELECTIONS

We performed a literature search, identifying relevant recent primary articles and review articles.

RESULTS

Dynamic crosstalk between the environmental factors and microbial, epithelial, and immune cells in the development of atopic dermatitis, allergic rhinitis, chronic rhinosinusitis, and asthma underlies the pathogenesis of these diseases. There is substantial evidence in the literature suggesting that environmental factors directly affect barrier function of the epithelium. In addition, T-helper 2 (T_H2) cells, type 2 innate lymphoid cells, and their cytokine interleukin 13 (IL-13) damage skin and lung barriers. The effects of environmental factors may at least in part be mediated by epigenetic mechanisms. Histone deacetylase activation by type 2 immune response has a major effect on leaky barriers and blocking of histone deacetylase activity corrects the defective barrier in human air-liquid interface cultures and mouse models of allergic asthma with rhinitis. We also present and discuss a novel device to detect and monitor skin barrier dysfunction, which provides an opportunity to rapidly and robustly assess disease severity.

CONCLUSION

A complex interplay between environmental factors, epithelium, and the immune system is involved in the development of systemic allergic diseases.

The Skin Microbiota and Itch: Is There a Link?

Itch is an unpleasant sensation that emanates primarily from the skin. The chemical mediators that drive neuronal activity originate from a complex interaction between keratinocytes, inflammatory cells, nerve endings and the skin microbiota, relaying itch signals to the brain. Stress also exacerbates itch via the skin–brain axis. Recently, the microbiota has surfaced as a major player to regulate this axis, notably during stress settings aroused by actual or perceived homeostatic challenge. The routes of communication between the microbiota and brain are slowly being unraveled and involve neurochemicals (i.e., acetylcholine, histamine, catecholamines, corticotropin) that originate from the microbiota itself. By focusing on itch biology and by referring to the more established field of pain research, this review examines the possible means by which the skin microbiota contributes to itch.

Safety considerations when using drugs to treat pruritus

Introduction: Treatment for chronic pruritus ranges from use of topical formulations to newer biologic agents. Targeting treatment to the underlying etiology is key in reducing the burden of disease while avoiding systemic or adverse effects.Areas covered: This review details the effective medical treatments used in various etiologies of chronic itch with a focus on the potential adverse effects and safety data available for each.Expert opinion: New drug developments in the areas of neural signaling and immune targeting show great promise for the future of chronic itch treatment. These new therapies broaden the available treatment options but also pose new considerations for safety and adverse effects.

Antipruritic Effects of Kappa Opioid Receptor Agonists: Evidence from Rodents to Humans

Centrally administered bombesin induces scratching and grooming in rats. These behaviors were blocked by early benzomorphan kappa opioid receptor (KOR) agonists as reported by Gmerek and Cowan in 1984. This was the first evidence that KORs may be involved in the sensation of itch-like behaviors. Subsequent development of additional animal models for acute and chronic itch has led to important discoveries since then. For example, it was found that (a) gastrin-releasing peptide (GRP), natriuretic polypeptide b and their cognate receptors are keys for the transmission of itch sensation at the spinal cord level, (b) dynorphins (Dyns), the endogenous KOR agonists, work as inhibitory neuromodulators of itch at the spinal cord level, (c) in a mouse model for acute itch, certain KOR antagonists elicit scratching, (d) in mouse models of acute or chronic itch, KOR agonists (e.g., U50,488, nalfurafine, CR 845, nalbuphine) suppress scratching induced by different pruritogens, and (e) nalfurafine, CR 845, and nalbuphine are in the clinic or in clinical trials for pruritus associated with chronic kidney disease and chronic liver disease, as well as pruritus in chronic skin diseases.

Management of Itch in the Elderly: A Review

Chronic itch is common in the elderly patient and may be caused by a variety of known dermatologic and non-dermatologic conditions and can have a significant effect on quality of life. Age-related changes in barrier function, immunosenescence, and neuronal changes and neuropathies are common predisposing factors to chronic itch in this age group. Certain primary dermatologic conditions are more common in the elderly and can cause chronic itch. Also, co-morbid diseases particularly of the renal, hepatobiliary, or hematologic systems, psychologic conditions, or medications may contribute to chronic itch in this population. Thus, medical workup for an elderly patient with chronic itch requires special attention to the patient's medical history, current health status, and medications. Topical treatments and emollients may be recommended for elderly patients, with consideration of specific adverse effects and alternatives. Systemic medications pose a higher risk of adverse effects and many are contraindicated in the elderly for this reason. In addition, management in the elderly may be complicated by differential pharmacokinetics of medications, the presence of co-morbid health conditions, cognitive disorders, physical limitations, and polypharmacy. New and emerging treatment modalities hold promise for use in the elderly due to these special considerations.