Chronic Pruritus in the Absence of Skin Disease: Pathophysiology, Diagnosis and Treatment

[Neuropathy in pruritus medicine : Recommended diagnostics and therapy]

Chronic itch is a frequent and debilitating condition that greatly affects the quality of life of those affected. In a subset of patients, damage to the peripheral or central nervous system constitutes the cause of the itch. Small-fiber neuropathy, nerve compression syndromes, post-herpetic neuralgia, scars and burns are possible conditions affecting the peripheral nervous system potentially causing itch, whereas space-occupying lesions affecting the spinal cord and stroke are examples of conditions that may induce central itch. Neuropathic itch starts on normal appearing skin, is often accompanied by pain sensations and other dysesthesias, and usually relieved by local cold application. Its distribution depends on the affected site of the somatosensory system. A comprehensive medical history is paramount to reach the diagnosis, while complementary diagnostics with skin biopsies for the investigation of cutaneous neuromorphological alterations or medical imaging to rule out nerve impingement may be advised in selected cases. Topical agents such as capsaicin or local anesthetics as well as systemic drugs such as gabapentinoids, antidepressants and opioid receptor modulators are used in the treatment of neuropathic itch. This review article provides an overview of the clinical features, underlying causes, diagnostic workup and therapeutic approach in neuropathic itch.

Electroacupuncture for relieving itching in atopic eczema: study protocol for a multicenter, randomized, sham-controlled trial

Background

Atopic eczema (AE) is a common atopic inflammatory skin disease affecting 2.1-4.9% of the population in different countries. Pruritus, one of the most burdensome symptoms, is often underestimated for the problems it can cause, creating a vicious loop of itching, scratching, and lichenification. Therefore, further research into practical and safe treatments that relieve itchy symptoms and enhance skin protection is key to overcoming AE. Acupuncture, with or without electrical stimulation, is one of the most commonly used therapeutic measures to treat AE. This trial aimed to objectively evaluate the efficacy and safety of the electroacupuncture (EA) antipruritic technique in AE pruritus and obtain high-level clinical evidence for the popularization and application of EA for AE.

Methods and analysis

This multicenter, single-blinded, randomized controlled trial is planned to transpire from April 15, 2023, to June 30, 2025. We will recruit 132 participants with AE (44 per group). Participants will be assigned randomly to three equal-sized groups: EA, sham electroacupuncture, and sham acupuncture. Treatment will be administered three times a week during the 2-week intervention phase. The primary outcome measure is the Visual Analog Scale, with a numeric rating scale to evaluate pruritus. Secondary outcome measures include the Eczema Area and Severity Index and Dermatology Life Quality Index. Other outcome measures include physical examination, serum IgE, and safety evaluation. The number, nature, and severity of adverse events will be carefully recorded.

Trial registration

ClinicalTrials.gov, 22Y11922200. Registered 3 September 2022, https://register.clinicaltrials.gov.

Peristomal Skin Itch: An Integrative Review

Survey data from the United Stated, the United Kingdom, and the Netherlands indicate peristomal itch is prevalant among ostomy patients. Pruritus has a significant negative impact on health-related quality of life, resulting in discomfort and interrupted sleep. In ostomy patients, peristomal skin scratching also may interfere with adherence of the ostomy pouching system. This article reviews the classification and pathophysiology of itch in the peristomal skin, along with options for its management.

Mild Skin Heating Evokes Warmth Hyperknesis Selectively for Histaminergic and Serotoninergic Itch in Humans

Chronic itch can severely affect quality of life. Patients report that their chronic itch can be exacerbated by exposure to warm conditions (“warmth hyperknesis”). The aim of this mechanistic study was to investigate the effect of mild heating of the skin in humans on various experimental models of itch. A total of 18 healthy subjects were recruited to the study. Itch was provoked by histamine, serotonin, or cowhage in 3 different sessions. The provoked area was heated with an infrared lamp, and the skin temperature was either not altered, or was increased by 4°C or 7°C. Subsequent to induction of itch, the itch intensity was recorded for 10 min while the skin was heated continuously throughout the entire period of itch induction. Heating the skin resulted in a significant increase in itch intensity when provoked by histamine or serotonin. It is possible that thermoception and pruriception interact and selectively produce a higher itch intensity in histaminergic and serotoninergic itch.

Neuropathic Itch: Routes to Clinical Diagnosis

Neuropathic itch occurs due to damage of neurons of the peripheral or central nervous system. Several entities, including metabolic, neurodegenerative, orthopedic, infectious, autoimmune, malignant, and iatrogenic conditions, may affect the somatosensory system and induce neuropathic itch. Due to the complex nature of neuropathic itch, particularly concerning its clinical presentation and possible etiological factors, diagnostic work-up of this condition is challenging. A detailed medical history, especially in regard to the itch, and a comprehensive physical examination are relevant to detect characteristic signs and symptoms of neuropathic itch and to rule out other possible causes for chronic itch. Complementary diagnostic exams, especially laboratory tests, determination of the intraepidermal nerve fiber density via a skin biopsy and radiological examinations may be indicated to confirm the diagnosis of neuropathic itch and to identify underlying etiological factors. Functional assessments such as quantitative sensory testing, nerve conduction studies, evoked potentials, or microneurography may be considered in particular cases. This review article provides a comprehensive overview of the diagnostic work-up recommended for patients with neuropathic itch.

Efficacy of a Topical Product Containing Purified Omental Lipids and Three Anti-Itching Compounds in the Treatment of Chronic Pruritus/Prurigo Nodularis in Elderly Subjects: A Prospective, Assessor-Blinded, 4-Week Trial with Transepidermal Water Loss and Optical Coherence Tomography Assessments

PURPOSE

To investigate the efficacy of a cream containing purified omental lipids 10% and three anti-itching substances (polidocanol/stimutex/palmitoylethanolamine) in elderly subjects with chronic pruritus/prurigo nodularis (CP/CPN).

PATIENTS AND METHODS

Thirty-five subjects (6 men; mean age 67±4 years) with CP/CPN were enrolled in a prospective, assessor-blinded, 4-week study. The cream was applied twice daily in the most affected body area. The primary endpoints were the evolution of the 10-cm visual analogue itch severity scale (VAS) and the 4-point verbal itching rating scale (VRS) (from 0 to 3). Secondary endpoints were the evolution of optical coherence tomography (OTC) of four skin parameters (acanthosis/hyperkeratosis/scale/dermal vascular pattern), assessed in a target lesioned area, and the transepidermal water loss (TEWL). Study endpoints were evaluated at baseline and after 2 and 4 weeks by an investigator unaware of the type of treatment.

RESULTS

All the enrolled subjects concluded the trial. At baseline, the mean±SD scores for VAS and VRS were 4.9±2.2 and 1.7±0.7, respectively. The treatment was associated with a significant reduction (p=0.0001) of VAS score of 60% at week 2 and of 86% at week 4. VRS score was significantly reduced by 49% after 2 weeks and by 81% after 4 weeks, in comparison with baseline. TEWL (expressed as g/m2/h) mean values were 18±5.4 at baseline and 12.7±4.4 at week 2 and 9.8±4.7 at week 4 (P=0.0001 vs baseline). All the OCT parameters evaluated improved during active treatment; acanthosis grade was 0.22 mm at baseline, 0.19 mm at week 2 and 0.17 mm at week 4 (p=0.0005), representing a 23% reduction in comparison with baseline. The product was very well tolerated.

CONCLUSION

This purified omental lipid with three anti-itching components cream reduces significantly itch intensity in subjects with chronic pruritus/prurigo nodularis, improving the skin barrier function and skin structure.

TRIAL NUMBER

ISRCTN869561669.

Pathophysiology, diagnosis, and pharmacological treatment of prurigo nodularis

Introduction: Prurigo nodularis (PN) is a chronic inflammatory skin disease characterized by intensely pruritic, hyperkeratotic nodules distributed on the trunk and extensor surfaces of the extremities. PN has a profoundly negative impact on sleep and quality of life in patients with PN. There are currently no U.S. Food and Drug Administration-approved agents and patients are often recalcitrant to current therapies, highlighting the importance of further research into this severely debilitating condition. Areas covered: A PubMed search was conducted to find available literature on the pathophysiology and clinical management of PN. In this review article, we discuss the current understanding of the pathophysiology, recommended diagnostic approach, and treatment options available for PN. Expert opinion/commentary: PN is an extremely difficult condition to treat, because there is a lack of effective therapies available due to our limited understanding of its pathophysiology. Currently, available treatment options are often multimodal due to the intersection of neuroimmune etiologic factors in the pathogenesis of PN. Fortunately, as our knowledge of PN expands, novel treatments targeting specific molecular biomarkers of PN are emerging, providing hope to this long-suffering patient population.

Matrix stimulation in chronic pruritus: A randomized controlled study

Chronic pruritus is one of the main symptoms in dermatology. We investigated a new intervention for chronic pruritus by neurostimulation through matrix electrodes. In this randomized controlled trial, 29 patients with chronic pruritus caused by a variety of dermatological diseases were allocated to an experimental group (EG; n = 14, 4-Hz neurostimulation of the itching area through matrix electrodes) or the control group (CG; n = 15, placement of matrix electrodes without neurostimulation). Outcome measures were the itching sensation as measured by a Numerical Rating Scale immediately after the intervention and the intermediate effect measured by the average itching sensation on the day before the intervention compared with the average itching sensation on day 1, 2 and 3 after the intervention. Regarding the short-term effect on itching, the anova showed a significant interaction effect for the 5-min stimulation with a larger reduction in the EG with a large effect size of d = 1.10. The average reduction in itching intensity was 78.2% for the EG compared with 34.3% for the CG. For the intermediate effect, no significant interaction was found (F = 1.721, P = 0.199). Comparing the itching sensation at day 0 with day 3, the interaction effect showed a statistical trend toward a greater reduction in the EG (F = 3.178, P = 0.086; statistical trend, d = 0.69). This study proved that neurostimulation through matrix electrodes is effective in the short-term reduction of itching in patients with chronic pruritus caused by dermatological diseases. Additional studies are needed with larger patient pools and covering longer study periods.

Generalized chronic itch induced by small-fibre neuropathy: clinical profile and proposed diagnostic criteria

BACKGROUND

Small-fibre neuropathy (SFN) is a known cause for pain, however, it may be also associated with chronic itch. The clinical profile of chronic itch due to SFN is poorly defined and accordingly under-diagnosed in clinical care.

OBJECTIVES

To establish the clinical profile of patients with SFN and to propose diagnostic criteria for this patient population.

METHODS

Clinical data from patients diagnosed with SFN [chronic generalized itch and reduced intraepidermal nerve fibre density (IENFD)] were analysed retrospectively.

RESULTS

A total of 142 patients (60 females, median age: 62.5 years) were included. Patients reported daily, moderate to severe itch intensity scores occurring mostly in attacks (62.5%). Only 11 patients experienced exclusively itch, while the remaining patients (92%) reported pruralgia (itch along with painful sensations). Burning (50%), a sensation like needle pricks (46%) and tingling (45%) were the sensory symptoms reported by most patients. Cold or ice application led to an alleviation of the symptoms. The IENFD did not correlate with itch intensity; however, patients with a severely reduced IENFD (<30% of the normative cut-off value) reported more frequently sharp, spiky and drilling sensations compared to the remaining patients. The quality of life was moderately impaired and correlated with itch intensity, whereas anxiety and depression scores were low.

CONCLUSIONS

Onset of pruralgia on normal appearing skin, occurrence in attacks and symptomatic alleviation with cold/ice application should alert physicians for a possible neuropathic SFN-related origin of itch. A reduced IENFD can confirm the diagnosis of SFN.

The NK1 receptor antagonist serlopitant for treatment of chronic pruritus

Introduction: Pruritus is a common symptom associated with several potential underlying causes, including both dermatologic and systemic diseases; it can also occur without an identifiable cause. Current treatment options are limited and most patients experience impaired quality of life. Serlopitant is a neurokinin 1 (NK₁) receptor antagonist under development for the treatment of pruritus associated with various dermatologic conditions and chronic pruritus of unknown origin. Areas covered: This review describes the epidemiology and unmet needs of patients with chronic pruritus, focusing specifically on patients with prurigo nodularis, psoriatic itch, and chronic pruritus of unknown origin; the rationale for targeting the NK₁ receptor for treatment of chronic pruritus; and the clinical development of serlopitant, including efficacy and safety data from completed phase II studies. Expert opinion: There is an unmet need for novel, safe, and effective therapies to treat chronic pruritus. Serlopitant has shown promising efficacy, safety, and tolerability across different patient populations, including adolescents and elderly patients. In contrast to less convenient administration options, serlopitant is a once-daily oral tablet, which is expected to facilitate compliance.

Maintaining skin health in older people

Skin changes associated with age are inevitable. Ageing is associated with structural and functional changes of the skin that result in increased vulnerability. The most common functional skin changes are dryness (xerosis), which causes itching and discomfort, and skin fragility, increasing patients' vulnerability to skin damage. Dry skin and itching have a significant effect on older people, which can be further exacerbated by products used for washing and bathing. The management of dry skin and itching is fundamental to older people's care and nurses should act in their best interests to ensure that the potential for skin damage is addressed. However, many older people are often reluctant to discuss the problem, are embarrassed and will self-treat or try to hide an underlying problem such as incontinence or worries about being infectious or dirty. This can be challenging when managing their skin care because of under-reporting, self-medicating or the assumption that it is 'just old age'.

Pruritus Associated with Targeted Anticancer Therapies and Their Management

Targeted anticancer therapies have significantly increased the survival of patients with a variety of malignancies, improving tolerability and treatment duration. The increased lifespan and the expanded use of targeted agents have led to a variety of treatment-related adverse events. Pruritus, a common dermatologic adverse event with various incidences ranging from 2.2% to 47% across different categories of targeted anticancer therapies, has been overlooked. This article reviews the incidence, accompanying skin conditions, possible pathomechanism, and proposed management algorithms of pruritus associated with targeted therapies, including immunotherapies.

A systematic review of evidence-based treatments for prurigo nodularis

Prurigo nodularis is a chronic dermatologic condition involving the development of multiple cutaneous nodules in the setting of intractable pruritus. Given emerging treatment options for this difficult-to-treat condition, a current review of therapeutics is needed. A systematic review was performed for clinical studies investigating prurigo nodularis treatment published from 1990 to present including ≥5 subjects. A total of 35 articles were assigned a level of evidence according to the Oxford Center for Evidence-based Medicine. All 5 studies investigating topical agents, including corticosteroids, calcineurin inhibitors, calcipotriol, and capsaicin, conveyed some beneficial effect with level of evidence 2b or higher. Six of 8 reports investigating photo- and photochemotherapy achieved levels of evidence 2b or greater and showed good partial response rates. Thalidomide was studied by 6 reports providing evidence of good symptom response, only 2 of which were rated level 2b or greater. Cyclosporine and methotrexate have demonstrated benefit in 4 combined studies, albeit with level 4 evidence. Pregabalin, amitriptyline, paroxetine, fluvoxamine, and neurokinin-1 receptor antagonists have demonstrated promising evidence in 5 level 2b studies. Higher-powered studies and additional randomized controlled trials are needed for the evaluation of safe and efficacious systemic treatment options for prurigo nodularis.

Medical applications of nonthermal atmospheric pressure plasma in dermatology

Plasma is an ionized gas that consists of positively and negatively charged particles, neutral atoms, and photons. Recent developments in plasma sources have made it possible to generate room-temperature plasma in the "open air", thus enabling the application of plasma in vivo. Using nonthermal plasma, active agents can be efficiently delivered to target cells without creating thermal damage. Also known as cold atmospheric pressure plasma (CAP), nonthermal atmospheric pressure plasma offers innovative medical applications. In this context, it has also gained wide attention in the field of dermatology. The complex and variable mixture of active agents in plasma - predominantly reactive oxygen and nitrogen species (ROS, RNS) - can control or trigger complex biochemical reactions, achieving the desired effects in a dose-dependent manner. The objective of the present review is to present potential applications of plasma in dermatology and analyze its potential mechanisms of action.

Assessing Pruritus in Hidradenitis Suppurativa: A Cross-Sectional Study

BACKGROUND

Pruritus is still a forgotten aspect of hidradenitis suppurativa (HS) and, to date, has never been adequately studied.

OBJECTIVE

The aim of this study was to determine the prevalence, and explore the characteristics, of pruritus in a well-defined cohort of HS patients.

SETTING

An academic hospital-based cross-sectional study in The Netherlands.

METHODS

A numerical rating scale (NRS, 0-10) was used to determine the prevalence of HS-related itch (NRS score ≥3). Candidate predictors for pruritus were subsequently determined using logistic regression models, and the impact of pruritus was assessed using a modified five-dimensional (5-D) itch scale. Associated serological and histological markers of pruritus were (semi-)quantitatively investigated in a subpopulation.

RESULTS

The prevalence rate of pruritus in 211 HS patients was 57.3%, with a mean NRS score of 6.1 ± 2.0. Patients with a pruritus NRS score ≥3 had more HS-affected body sites than patients with a score <3 (p < 0.001). The occurrence of a pruritus NRS score ≥3 was associated with Hurley III disease (odds ratio [OR] 7.73; p = 0.003) and pain (OR 1.34; p < 0.001). Pruritus affected sleep and activities of daily living (ADL) in the majority of cases, with an associated modified 5-D itch score of 13.7 ± 3.6 (on a scale from 5 to 25) in 52 HS patients. Histological examination showed eosinophilic granulocytes were present in 25% (2/8) of the perilesional skin and 63% (10/16) of the lesional skin, while a perineural infiltrate was found in 25% (2/8) and 69% (11/16) of the perilesional and lesional skin, respectively.

CONCLUSION

Pruritus is a frequent but underreported symptom in patients with HS. Its moderate to severe intensity and significant impact on daily activities have great potential to impair patients' quality of life.