Prurigo nodularis: Epidemiology and clinical features

Systemic Medication for the Treatment of Prurigo Nodularis-A Systematic Review

IMPORTANCE

Prurigo nodularis (PN) is a debilitating inflammatory skin disease characterized by red to violaceous pruritic lesions. The goal of therapy is to break the scratch-itch cycle. Treatment varies and often requires a multimodal approach to target both immune and neural mediated aspects of disease.

OBJECTIVES

To review the efficacy of systemic treatment used to treat PN.

EVIDENCE REVIEW

A systematic search of keywords and Medical Subject Headings was performed in Ovid MEDLINE, Embase, Scopus, and ClinicalTrials.gov. The first 200 results of an abbreviated search in Google Scholar were also included. PRISMA guidelines were followed and the review was registered on PROSPERO (CRD42023412012). GRADE criteria were used to assess articles for quality of evidence.

FINDINGS

The search resulted in 1153 articles; 382 were duplicates, 643 were irrelevant, 19 were not retrieved, 21 were abstract only, and 88 are included in this review. There were 24 studies on dupilumab, 16 on thalidomide, 8 on cyclosporin, 7 on methotrexate, 3 each on lenalidomide and aprepitant, 2 each on alitretinoin, apremilast, baricitinib, gabapentin, intravenous (IV) immunoglobulins, pregabalin, tofacitinib, and 1 each on amitriptyline, azathioprine, butorphanol, isoquercitin, IV dexamethasone-cyclophosphamide/ oral cyclophosphamide, ketotifen, metronidazole, montelukast, nalbuphine, nemolizumab, serolopitant, tacrolimus, and herose derma zima capsule.

CONCLUSIONS AND RELEVANCE

Dupilumab reduces pruritus and appearance of lesions and is associated with the fewest number of side effects. Thalidomide and pregabalin are also effective, but their long-term use is limited by muscle and nerve pain. Janus Kinase inhibitors may be beneficial, but large population studies are lacking.

Phase 3 Trial of Nemolizumab in Patients with Prurigo Nodularis

BACKGROUND

Prurigo nodularis is a chronic, debilitating, and severely pruritic neuroimmunologic skin disease. Nemolizumab, an interleukin-31 receptor alpha antagonist, down-regulates key pathways in the pathogenesis of prurigo nodularis.

METHODS

In this phase 3, double-blind, multicenter, randomized trial, we assigned adults with moderate-to-severe prurigo nodularis to receive an initial 60-mg dose of nemolizumab followed by subcutaneous injections of 30 mg or 60 mg (depending on baseline weight) every 4 weeks for 16 weeks or matching placebo. The primary end points were an itch response (a reduction of ≥4 points on the Peak Pruritus Numerical Rating Scale [PP-NRS; scores range from 0 to 10, with higher scores indicating more severe itch]) and an Investigator's Global Assessment (IGA) response (a score of 0 [clear] or 1 [almost clear] on the IGA [scores range from 0 to 4] and a reduction from baseline to week 16 of ≥2 points). There were five key secondary end points.

RESULTS

A total of 274 patients underwent randomization; 183 were assigned to the nemolizumab group, and 91 to the placebo group. Treatment efficacy was shown with respect to both primary end points at week 16; a greater percentage of patients in the nemolizumab group than in the placebo group had an itch response (56.3% vs. 20.9%; strata-adjusted difference, 37.4 percentage points; 95% confidence interval [CI], 26.3 to 48.5), and a greater percentage in the nemolizumab group had an IGA response (37.7% vs. 11.0%; strata-adjusted difference, 28.5 percentage points; 95% CI, 18.8 to 38.2) (P<0.001 for both comparisons). Benefits were observed for the five key secondary end points: itch response at week 4 (41.0% vs. 7.7%), PP-NRS score of less than 2 at week 4 (19.7% vs. 2.2%) and week 16 (35.0% vs. 7.7%), and an improvement of 4 or more points on the sleep disturbance numerical rating scale (range, 0 [no sleep loss] to 10 [unable to sleep at all]) at week 4 (37.2% vs. 9.9%) and week 16 (51.9% vs. 20.9%) (P<0.001 for all comparisons). The most common individual adverse events were headache (6.6% vs. 4.4%) and atopic dermatitis (5.5% vs. 0%).

CONCLUSIONS

Nemolizumab monotherapy significantly reduced the signs and symptoms of prurigo nodularis. (Funded by Galderma; ClinicalTrials.gov number, NCT04501679; EudraCT number, 2019-004789-17.).

Validation of the Peak Pruritus Numerical Rating Scale as a Patient-Reported Outcome Measure in Prurigo Nodularis

INTRODUCTION

Validated patient report tools for quantifying patient experiences of itch in prurigo nodularis (PN) are limited. This study aimed to evaluate the validity of the 11-point peak pruritus numerical rating scale (PP NRS) as a single-item patient-reported outcome (PRO) measure for assessing itch severity in PN.

METHODS

Content validity of the PP NRS was evaluated through qualitative interviews with adults with PN. The PP NRS was then psychometrically evaluated using data from a placebo-controlled trial of nemolizumab in adults with PN, during which patients completed the PP NRS daily. Meaningful within-patient change was estimated from the qualitative interviews and by anchor- and distribution-based analyses of trial data.

RESULTS

The interview participants (N = 21) all understood the PP NRS and reported itch as their worst symptom overall. The PP NRS showed good test-retest reliability and demonstrated convergent validity and known-groups validity. PP NRS scores improved more in patients classified as "improved" on other clinical outcome measures than in those classified as "worsened/unchanged". Triangulation of the different estimates identified a 2- to 5-point decrease in PP NRS score as a meaningful within-patient change threshold.

CONCLUSION

The PP NRS is a content-valid and reliable PRO measure for quantifying itch severity in adults with PN in clinical trials.

TRIAL REGISTRATION NUMBER

NCT03181503.

Somatic mutations reveal hyperactive Notch signaling and racial disparities in prurigo nodularis

Prurigo nodularis (PN) is a chronic inflammatory skin disease that disproportionately affects African Americans and is characterized by pruritic skin nodules of unknown etiology. Little is known about genetic alterations in PN pathogenesis, especially relating to somatic events which are often implicated in inflammatory conditions. We thus performed whole-exome sequencing on 54 lesional and nonlesional skin biopsies from 17 PN patients and 10 atopic dermatitis (AD) patients for comparison. Somatic mutational analysis revealed that PN lesional skin harbors pervasive somatic mutations in fibrotic, neurotropic, and cancer-associated genes. Nonsynonymous mutations were most frequent in NOTCH1 and the Notch signaling pathway, a regulator of cellular proliferation and tissue fibrosis, and NOTCH1 mutations were absent in AD. Somatic copy-number analysis, combined with expression data, showed that recurrently deleted and downregulated genes in PN lesional skin are associated with axonal guidance and extension. Follow-up immunofluorescence validation demonstrated increased NOTCH1 expression in PN lesional skin fibroblasts and increased Notch signaling in PN lesional dermis. Finally, multi-center data revealed a significantly increased risk of NOTCH1-associated diseases in PN patients. In characterizing the somatic landscape of PN, we uncover novel insights into its pathophysiology and identify a role for dysregulated Notch signaling in PN.

Atopic Dermatitis Across Shades of Skin

Atopic dermatitis (AD) is a chronic, heterogeneous inflammatory skin disease that is associated with immense patient burden globally. There is increasing appreciation of disparities among patients identified as having skin of color (SOC), which often refers to patients of non-White race or non-European ancestry, but can broadly include individuals from a number of different racial, ethnic, ancestral, and skin pigmentation groups based on definition. In this narrative review, we discuss key terminology as it relates to AD across shades of skin, including modern definitions of 'race', 'ethnicity', and 'SOC'. We then synthesize the current literature describing disparities in AD prevalence, disease recognition, and burden alongside current data regarding genetic and immunologic findings across SOC populations. In the context of these findings, we highlight key concomitant social determinants of health, including environmental factors, socioeconomic status, and access to care, for which race often serves as a proxy for true biological and genetic differences. Finally, we discuss future efforts to shift to a more inclusive understanding of AD to encompass all shades of skin, to ensure equitable representation of diverse populations in high impact research, and intensify efforts to address the critical upstream factors driving observed disparities.

Modulation of Neuroimmune and Epithelial Dysregulation in Patients With Moderate to Severe Prurigo Nodularis Treated With Nemolizumab

Importance

Prurigo nodularis (PN) is a debilitating skin disease characterized by intense pruritus and hyperkeratotic skin nodules. Nemolizumab, a monoclonal antibody targeting interleukin 31 receptor α, is a promising novel therapy for the treatment of moderate to severe PN. The biological mechanisms by which nemolizumab promotes improvement of itch and skin lesions in PN are unknown.

Objective

To characterize changes in plasma protein biomarkers associated with clinical response to nemolizumab in patients with PN.

Design, Setting, and Participants

This multicenter cohort study included patients recruited from Austria, France, Germany, Poland, and the US from a phase 2 clinical trial. Adults diagnosed with moderate to severe PN with severe pruritus for at least 6 months were included in the original trial. Patients in the nemolizumab group were included in the present study if they achieved at least a 4-point decrease in the Peak Pruritus Numerical Rating Scale (PP-NRS) from baseline to week 12 during nemolizumab treatment. Placebo controls did not experience a 4-point decrease in PP-NRS. Mass spectrometry with tandem mass tags to enrich skin-specific protein detection was used to characterize changes in plasma protein expression in nemolizumab and placebo groups. Data were collected from November 2, 2017, to September 26, 2018, and analyzed from December 6, 2019, to April 8, 2022.

Intervention

As part of the clinical trial, patients were treated with 3 doses of nemolizumab or placebo at 0, 4, and 8 weeks.

Main Outcomes and Measures

Changes in plasma and epidermal protein expression in nemolizumab-treated patients compared with the placebo group at 0, 4, and 12 weeks.

Results

Among the 38 patients included in the analysis (22 women and 16 men; mean [SD] age, 55.8 [15.8] years), enrichment analysis of canonical pathways, biological functions, and upstream regulators showed downregulation of terms involving inflammation (IL-6, acute-phase response, signal transducer and activator of transcription 3, and interferon γ), neural processes (synaptogenesis signaling and neuritogenesis), tissue remodeling and fibrosis (transforming growth factor β1 and endothelin-1), and epidermal differentiation (epithelial mesenchymal transition) in the plasma of nemolizumab group.

Conclusions and Relevance

In this cohort study, differences between nemolizumab and placebo groups included modulation of inflammatory signaling, neural development, and epithelial differentiation, suggesting a promising potential approach for clinical management of PN.

Single-cell RNA sequencing defines disease-specific differences between chronic nodular prurigo and atopic dermatitis

BACKGROUND

Chronic nodular prurigo (CNPG) is an inflammatory skin disease that is maintained by a chronic itch-scratch cycle likely rooted in neuroimmunological dysregulation. This condition may be associated with atopy in some patients, and there are now promising therapeutic results from blocking type 2 cytokines such as IL-4, IL-13, and IL-31.

OBJECTIVES

This study aimed to improve the understanding of pathomechanisms underlying CNPG as well as molecular relationships between CNPG and atopic dermatitis (AD).

METHODS

We profiled skin lesions from patients with CNPG in comparison with AD and healthy control individuals using single-cell RNA sequencing combined with T-cell receptor sequencing.

RESULTS

We found type 2 immune skewing in both CNPG and AD, as evidenced by CD4+ helper T cells expressing IL13. However, only AD harbored an additional, oligoclonally expanded CD8A+IL9R+IL13+ cytotoxic T-cell population, and immune activation pathways were highly upregulated in AD, but less so in CNPG. Conversely, CNPG showed signatures of extracellular matrix organization, collagen synthesis, and fibrosis, including a unique population of CXCL14-IL24+ secretory papillary fibroblasts. Besides known itch mediators such as IL31 and oncostatin M, we also detected increased levels of neuromedin B in fibroblasts of CNPG lesions compared with AD and HC, with neuromedin B receptors detectable on some nerve endings.

CONCLUSIONS

These data show that CNPG does not harbor the strong disease-specific immune activation pathways that are typically found in AD but is rather characterized by upregulated stromal remodeling mechanisms that might have a direct impact on itch fibers.

The Sleep Disturbance Numerical Rating Scale: Content Validity, Psychometric Validation, and Meaningful Within-Patient Change in Prurigo Nodularis

INTRODUCTION

Sleep is often disturbed in patients with prurigo nodularis (PN). To address the lack of validated patient-reported outcome (PRO) measures for quantifying sleep disturbance in PN, we evaluated the Sleep Disturbance Numerical Rating Scale (SD NRS) as a single-item PRO measure for quantifying sleep disturbance in PN.

METHODS

Adults with PN participated in qualitative interviews, which included concept elicitation and cognitive debriefing of the SD NRS. The SD NRS was evaluated psychometrically using data from a phase 2 randomized trial in adults with PN (NCT03181503). Other PRO assessments included the Average Pruritus (AP) NRS, AP Verbal Rating Scale (VRS), peak pruritus (PP) NRS, PP VRS, and Dermatology Life Quality Index (DLQI). Reliability, validity, and responsiveness of the SD NRS were evaluated, and meaningful within-patient change was estimated from qualitative interview responses and quantitative trial data.

RESULTS

All interview participants (N = 21) experienced sleep disturbance and most (95%) understood the SD NRS as intended. The SD NRS demonstrated test-retest reliability based on intra-class correlation coefficients for itch-stable participants of 0.87 for the AP VRS and 0.76 for the PP VRS. At baseline, Spearman's rank-order correlation coefficients were moderate to strong (0.3-0.8) between the SD NRS and the AP NRS, AP VRS, PP NRS, PP VRS, and DLQI. Known-groups validity was demonstrated by higher (worse) SD NRS scores in participants with worse scores on the AP NRS, AP VRS, PP VRS, and DLQI. Improvements in SD NRS scores were greater in participants classified as "improved" versus "worsened/unchanged" on the anchor PROs. A 2- to 4-point decrease on the 11-point SD NRS scale was identified as a meaningful within-patient change.

CONCLUSION

The SD NRS is a well-defined, reliable, and valid PRO measure that can be used in daily practice and clinical trials to capture sleep disturbance in adults with PN.

Dupilumab in patients with prurigo nodularis: two randomized, double-blind, placebo-controlled phase 3 trials

Prurigo nodularis (PN) is a chronic inflammatory skin disease with intensely pruritic nodules. The LIBERTY-PN PRIME and PRIME2 phase 3 trials enrolled adults with PN with ≥20 nodules and severe itch uncontrolled with topical therapies. Dupilumab, a fully human monoclonal antibody, blocks the shared receptor component for interleukin (IL)-4 and IL-13. Patients were randomized 1:1 to 300 mg dupilumab or placebo subcutaneously every 2 weeks for 24 weeks. The primary endpoint was pruritus improvement, measured by proportion of patients with a ≥4-point reduction in Worst Itch Numeric Rating Scale (WI-NRS) from baseline at week 24 (PRIME) or week 12 (PRIME2). Key secondary endpoints included nodule number reduction to ≤5 at week 24. PRIME and PRIME2 enrolled 151 and 160 patients, respectively. Both trials met all the pre-specified primary and key secondary endpoints. A ≥4-point WI-NRS reduction at week 24 in the dupilumab and placebo arms was achieved by 60.0% and 18.4% of patients, respectively, in PRIME (95% confidence interval (CI), 27.8-57.7 for the difference, P < 0.001) and at week 12 by 37.2% and 22.0% of patients, respectively, in PRIME2 (95% CI, 2.3-31.2; P = 0.022). Dupilumab demonstrated clinically meaningful and statistically significant improvements in itch and skin lesions versus placebo in PN. Safety was consistent with the known dupilumab safety profile.ClinicalTrials.gov identifiers: NCT04183335 and NCT04202679 .

The blood proteomic signature of prurigo nodularis reveals distinct inflammatory and neuropathic endotypes: A cluster analysis

BACKGROUND

Prurigo nodularis (PN) is an extremely pruritic, chronic inflammatory skin disease. Little is known about systemic inflammation in PN.

OBJECTIVE

To characterize plasma inflammatory biomarkers in patients with PN and investigate the presence of disease endotypes.

METHODS

In this cross-sectional study, Olink proteomic analysis was performed on plasma samples from patients with PN (n = 29) and healthy controls (n = 18).

RESULTS

Patients with PN had increased levels of 8 circulating biomarkers compared to controls, including tumor necrosis factor, C-X-C Motif Chemokine Ligand 9, interleukin-12B, and tumor necrosis factor receptor superfamily member 9 (P < .05). Two PN clusters were identified in cluster 1 (n = 13) and cluster 2 (n = 16). Cluster 2 had higher levels of 25 inflammatory markers than cluster 1. Cluster 1 had a greater percentage of patients with a history of myelopathy and spinal disc disease compared with cluster 2 (69% vs 25%, P = .03). Patients in cluster 2 were more likely to have a history of atopy (38% in cluster 2 vs 8% in cluster 1, P = .09).

LIMITATIONS

Small sample size precludes robust subgroup analyses.

CONCLUSION

This study provides evidence of neuroimmune-biased endotypes in PN and can aid clinicians in managing patients with PN that are nonresponsive to traditional therapies.

Skin Microbiome in Prurigo Nodularis

Prurigo nodularis (PN) is a chronic condition characterized by the presence of nodular lesions accompanied by intense pruritus. The disease has been linked to several infectious factors, but data on the direct presence of microorganisms in the lesions of PN are scarce. The aim of this study was to evaluate the diversity and composition of the bacterial microbiome in PN lesions by targeting the region V3-V4 of 16S rRNA. Skin swabs were obtained from active nodules in 24 patients with PN, inflammatory patches of 14 patients with atopic dermatitis (AD) and corresponding skin areas of 9 healthy volunteers (HV). After DNA extraction, the V3-V4 region of the bacterial 16S rRNA gene was amplified. Sequencing was performed using the Illumina platform on the MiSeq instrument. Operational taxonomic units (OTU) were identified. The identification of taxa was carried out using the Silva v.138 database. There was no statistically significant difference in the alpha-diversity (intra-sample diversity) between the PN, AD and HV groups. The beta-diversity (inter-sample diversity) showed statistically significant differences between the three groups on a global level and in paired analyses. Staphylococcus was significantly more abundant in samples from PN and AD patients than in controls. The difference was maintained across all taxonomic levels. The PN microbiome is highly similar to that of AD. It remains unclear whether the disturbed composition of the microbiome and the domination of Staphylococcus in PN lesions may be the trigger factor of pruritus and lead to the development of cutaneous changes or is a secondary phenomenon. Our preliminary results support the theory that the composition of the skin microbiome in PN is altered and justify further research on the role of the microbiome in this debilitating condition.

Dupilumab Therapy of Prurigo Nodularis: A Single-Center, Real-Life Observational Study

Prurigo nodularis (PN) is a chronic inflammatory skin disease characterized by severe itching accompanied by multiple nodules throughout the body. There is currently no effective drug-targeted treatment for PN. Dupilumab is a fully human monoclonal antibody which can suppress the Th2 inflammatory reaction. We aimed to assess the efficacy and safety of dupilumab in PN. There were 29 PN patients who received dupilumab treatment for four months. Serum total immunoglobulin E (Ig E), eosinophil counts, dermatology life quality index (DLQI), and numeric rating scale (NRS) were assessed on patients before and after treatment. We count the vaccination of novel coronavirus pneumonia (COVID-19) in patients and the impact on PN and treatment measures after vaccination. Plotting was performed using GraphPad Prism8, and the statistical analysis was performed using PASW Statistics18. The eosinophil counts in patients higher decreased to normal, and the Ig E levels gradually decreased and tended to normal levels after receiving dupilumab injection. The average DLQI score at the baseline was 23.93 ± 0.66 and decreased to 11.66 ± 0.55 ( $P<0.01$ ) and 1.83 ± 0.22 ( $P<0.01$ ) at 1-month and 6-monthfollow-up of treatment, respectively. The average NRS score at the baseline was 9.79 ± 0.08 and decreased to 3.52 ± 0.23 ( $P<0.01$ ) and 0.31 ± 0.15 ( $P<0.01$ ) at the 1-month and 6-monthfollow-up of treatment, respectively. Our study shows that dupilumab has achieved good efficacy in PN with few adverse reactions and high safety. We can recommend that patients follow the advice of specialists to be vaccinated and under the condition of stable disease, separated from dupilumab treatment for one week.

A real-world observational study of dupilumab treatment in adult patients with prurigo nodularis

BACKGROUND

Prurigo nodularis (PN) is a chronic inflammatory skin condition that has a significant unmet needs for effective treatment options.

OBJECTIVE

To assess the efficacy and safety of dupilumab in adult patients with PN refractory to traditional therapies.

METHODS

This ongoing, real-life study examined dupilumab treatment in 8 adult patients diagnosed with PN for at least 6 months. The included patients were prescribed 300 mg dupilumab biweekly for at least 16 weeks. Efficacy was the primary outcome by means of multiple standardized scale measurements while safety was also reported.

RESULTS

PN patients treated with dupilumab showed notable clinical improvement. After 16 weeks of dupilumab treatment, the mean Investigator Global Assessment (IGA) score reduced from 3.75 to 1.50. Patients mean Numerical Rating Scale Itch Intensity (NRSI), Dermatology Life Quality Index (DLQI), and Hospital Anxiety and Depression Scale (HADS) ratings reduced from 8.625, 15.13, and 14.50 to 1.563, 4.625, and 1.000 respectively. The majority of the patients (87.5%) reported dupilumab as effective while no adverse events have been reported.

STUDY LIMITATIONS

This study was limited to a small cohort of adult PN patients and a short-time observation period.

CONCLUSIONS

Dupilumab is effective and tolerable in adult PN patients with significant improvement in skin lesions, itching, and quality of life.

Evaluation of risk in chronic cutaneous inflammatory conditions for malignant transformation

Skin carcinomas are the most common form of cancer, and every year thousands of people die from skin cancer-related malignancies. Chronic inflammation is linked to the development and progression of cancer in multiple organ systems - about 20% of all human cancers are a result of chronic inflammation - skin included. While acute inflammation under normal circumstances is a mechanism for host defence and tissue regeneration following insult by trauma or infection by pathogens, over the long term it can drive oncogenic transformation of epithelial cells and promote cancer development, growth and metastasis. Therefore, inflammatory conditions may put individuals at a higher risk to developing skin malignancies. Many skin conditions are characterized by chronic inflammatory processes. These conditions may be particularly susceptible to malignant transformation and predispose patients to develop skin malignancies. As more pathophysiology of chronic inflammatory skin conditions is unveiled, we find that many of these conditions are characterized by immune dysregulation and signalling that result in chronic activation and upregulation of pro-inflammatory chemokines and cytokines, leading to downstream processes that further exacerbate inflammatory processes and cause abnormal cell growth and apoptosis. Here, we review the major chronic cutaneous inflammatory diseases that may have an increased risk of skin malignancies, including atopic dermatitis, psoriasis, discoid lupus erythematosus, lichen planus, hidradenitis suppurativa, prurigo nodularis, lichen sclerosus, systemic sclerosis and morphea, chronic leg ulcers, seborrheic keratoses and basal cell carcinoma. We evaluate the evidence for increased incidence and prevalence, the risk factors associated, the populations at heightened risk and the best management practices.

Generalized prurigo nodularis with dramatic response to dupilumab treatment: A case report

BACKGROUND

Prurigo nodularis (PN) is a chronic condition characterized by a papulonodular pruriginous eruption of unknown aetiology. Currently, there are no medications for PN that the United States Food and Drug Administration has approved, which leads to very variable practices in the prescription of off-label treatments. Treatment of PN is based on clinical experience rather than controlled trials. We present our case of generalized PN, in which we had a dramatic response with dupilumab.

CASE SUMMARY

A 58-year-old female patient was admitted to our clinic with severe itchy, erythematous nodular lesions that were widespread all over her body, especially on the legs and back. It was learned that the patient's complaints started 4 years ago, and there was a significant increase in the lesions in the last period. Dermatological examination revealed diffuse firm erythematous excoriated nodular lesions all over the body. In the blood tests of the patient, serum Immunoglobulin E (IgE) was measured at 9330 IU/mL. The patient was diagnosed with generalized prurigo nodularis together with clinical and histopathological findings. Due to severe clinical findings and the presence of comorbidities, dupilumab treatment was planned for the patient. In the follow-up 4 mo later, it was observed that all nodular lesions healed with postinflammatory hypopigmentation. The IgE value decreased to 1500 IU/mL after 4 mo of dupilumab treatment.

CONCLUSION

Dupilumab treatment stands out as an effective and safe systemic treatment agent among existing systemic treatments.

RNA sequencing reveals the transcriptome profile of the atopic prurigo nodularis with severe itching

Prurigo nodularis (PN), characterized by inevitable chronicity and severe pruritus, is most frequently associated with atopy compared with other origins. However, the skin transcriptomic profiling of PN arising from atopic dermatitis (AD), so-called atopic PN (APN), remains unclear. We sought to explore the cutaneous transcriptome of APN with severe pruritus and compare it with classic AD. RNA sequencing was performed on the lesional skin from 13 APN to 11 AD patients with severe pruritus (itch numerical rating scale score ≥ 7) and normal skin from 11 healthy subjects. Quantitative real-time polymerase chain reaction and immunochemistry were used for validation. We detected 1085 and 1984 differentially expressed genes (DEGs) in lesional APN skin and lesional AD skin versus normal skin, respectively. In total, 142 itch/inflammation-related DEGs were identified. Itch/inflammation-related DEGs, such as IL-6, IL-10, IL-13, oncostatin M, and IL-4 receptor, had elevated gene transcript levels in both diseases. The itch/inflammation-related DEGs that increased only in APN were mainly neuroactive molecules, while many inflammatory mediators such as T helper 22-related genes were found to be increased only in AD. Both disorders showed mixed Th1/Th2/Th17 polarisation and impaired skin barrier. In contrast to AD, M1/M2 macrophage activation, tumor necrosis factor production, fibrosis, revascularization and neural dysregulation are unique features of APN. The study findings broaden our understanding of the pathogenesis underlying APN, which provides insights into novel pathogenesis with potential therapeutic implications.

[Translated article] Chronic Nodular Prurigo: A Retrospective Study of 74 Cases

BACKGROUND AND OBJECTIVE

Chronic nodular prurigo (CNPG) is a recently defined and currently underdiagnosed disease with a variety of causes. It is associated with multiple comorbidities, and its management and treatment have improved with a better understanding of its pathogenesis. The aim of this study was to describe our experience with a series of patients with CNPG.

MATERIAL AND METHODS

Single-center, observational, retrospective study of the sociodemographic and clinical characteristics of patients with CNPG seen at the dermatology department of a tertiary care hospital between 2009 and 2021.

RESULTS

We included 74 patients, mostly women (63.5%), with a mean age of 57 years. Overall, 39.2% of patients had a concomitant skin condition, mainly atopic dermatitis (62%). Other comorbidities included endocrine disorders (54.1%), cardiovascular disease (44.4%), and psychiatric disorders (36.5%). Skin biopsy helped confirm the clinical diagnosis in 70% of cases. The mean immunoglobulin E level was higher than normal (516IU/mL), regardless of atopic predisposition. On average, patients received three treatments, the most common choices being methotrexate, antihistamines, and topical and oral corticosteroids. Methotrexate was among the most effective options.

CONCLUSIONS

CNPG is a complex disease associated with multiple comorbidities. It requires a multidisciplinary approach, with the dermatologist at the center. Classical treatment approaches are probably insufficient.

Impact of Chronic Kidney Disease Severity on the Risk of Prurigo Nodularis: A Population-Based Cohort Study

While dialysis is linked with prurigo nodularis, little is known about the impact of non-dialysis chronic kidney disease on prurigo nodularis. The influence of chronic kidney disease on development of prurigo nodularis was measured using the Korean National Health Insurance and National Health Screening Program data, identifying 17,295,576 individuals without prior prurigo nodularis. Chronic kidney disease severity was determined by the estimated glomerular filtration rate (in ml/min/1.73 m²) calculated from serum creatinine, and proteinuria detected with urine dipstick. Prurigo nodularis incidence during follow-up was determined. Over a median follow-up period of 9.72 years, 58,599 individuals developed prurigo nodularis, with an incidence rate of 3.59 per 10,000 person-years. Among different variables, estimated glomerular filtration rate was the strongest risk factor for prurigo nodularis. Compared with estimated glomerular filtration rate ≥ 90, estimated glomerular filtration rate 15–29 (hazard ratio 1.31, 95% confidence interval 1.05–1.62) and end-stage renal disease (hazard ratio 1.46, 95% confidence interval 1.25–1.69) were associated with higher risks. The presence of proteinuria independently increased the risk of prurigo nodularis, increased risks associated with estimated glomerular filtration rate 15–29 and endstage renal disease, and caused risk associated with estimated glomerular filtration rate 30–59 to become significant. With differential impact of chronic kidney disease severity on the risk of prurigo nodularis, preservation of renal function would potentially translate into lower risk of prurigo nodularis.

Efficacy of dupilumab in chronic prurigo and chronic idiopathic pruritus: A systematic review of current evidence and analysis of response predictors

Dupilumab has demonstrated a great reduction on chronic pruritus that is the hallmark of atopic dermatitis (AD). Underscoring relevant pathogenesis similarities emerging from AD, chronic idiopathic pruritus (CIP) and chronic prurigo (CP), several authors suggested the beneficial role of dupilumab in these conditions. The evidence on this subject is limited with no precise data available. In this study, we carried out a systematic literature review in order to evaluate the efficacy of dupilumab on both pruritus and skin manifestations in the two largest retrospective cohorts of patients with CP and CIP and tried to identify potential response predictors. Electronic searches were conducted on 4 databases. Our primary outcome was the improvement in pruritus measured by a reduction in patient's reported numerical rating scale of itch (NRSI) by > 4. Secondary outcomes included: proportion of patients with complete response at the end of treatment, reduction in the number of lesions by the Investigator Global Assessment (IGA), improvement in numerical rating scale of sleep (NRSS), improvement in quality of life measured by the Dermatology Life Quality Index (DLQI), time until patient perceived any improvement (Time-First) and time until patient reported absence of pruritus (Time-Final). Descriptive statistics were calculated for each demographic and clinical variable. Univariate logistic regression analyses were conducted to explore association between response to dupilumab and potential predictive factors. We included 25 articles in the analysis, counting a total of 153 patients. Based on CP patients' cohort (n=132), the mean NRSI at baseline was 8.79 ±0.86 and the NRSI final was 2.32 ±1.27. The mean time to first improvement was 5.18 ±3.13 weeks, while the time to complete improvement of pruritus (Time-final) was 13.6 ±12.0 weeks. Ninety patients out of 109 (83%) noticed improvement in pruritus before 4 weeks of dupilumab therapy. At the end of treatment, 18 patients out of 126 (14%) had a complete remission of pruritus and 110 patients out of 123 (89%) had a reduction of NRSI > 4. The reduction in NRSI was significantly greater in patients improving before 4 weeks of treatment (6.57 ±1.71) compared to patients improving in more than 4 weeks (5.49 ±1.39, p<0.001). Patients with history of AD and those who have been previously treated with cyclosporine or methotrexate had a significantly lower reduction in NRSI (e.g. 6.05 ±1.34 vs 7.08 ±1.90 p<0.01 for non-associated AD patients). Based on CIP patient's cohort (n=21), the mean NRSI at baseline was 8.33 ±0.80 and the NRSI final was 0.95 ±0.59. The mean time to first improvement was 2 ±0 weeks, while the time to complete improvement (Time-final) was 14.6 ±10 weeks. At the end of treatment, 3 patients out of 21 (14%) had a complete remission of pruritus and 100% of patients had a reduction of NRSI > 4. No serious treatment-emergent adverse events were reported. The most common adverse event was mild conjunctivitis (13 cases). We highlight the importance of one early sign of improvement as predictor of the future response to dupilumab: the improvement before 4 weeks of treatment that leads significantly to a greater final reduction in NRSI. Furthermore, patients with the presence or history of atopy appear to be less responsive to dupilumab than non-atopic patients and develop more side effects, in particular conjunctivitis.

Immunotargets and Therapy for Prurigo Nodularis

Prurigo nodularis is a chronic inflammatory skin disease consisting of severely pruritic nodules that can be very debilitating for patients. The basis of this skin condition is immunological dysregulation and neural amplification, driven by T-lymphocytes, mast cells, eosinophilic granulocytes, macrophages, and cytokines mediating itchy processes. Further complicating this already taxing diagnosis is the lack of approved treatment and consensus on management; although there are off-label treatments utilized as therapy. Immunomodulators are the cornerstone of treatment for PN, and additional novel therapies targeting key players in the immunological cascade are currently undergoing investigation. In this review, we will highlight targets of the immune cascade and explore current immunomodulating treatments as well as immunotherapies on the horizon for the management of prurigo nodularis.

Epidemiology, Comorbidities, and Prescription Patterns of Korean Prurigo Nodularis Patients: A Multi-Institution Study

Prurigo nodularis (PN) is a chronic dermatosis typified by extraordinarily itchy nodules. However, little is known of the nature and extent of PN in Asian people. This study aimed to describe the epidemiology, comorbidities, and prescription pattern of PN in Koreans based on a large dermatology outpatient cohort. Patients with PN were identified from the Catholic Medical Center (CMC) clinical data warehouse. Anonymized data on age, sex, diagnostic codes, prescriptions, visitation dates, and other relevant parameters were collected. Pearson correlation analysis was used to calculate the correlation between PN prevalence and patient age. Conditional logistic regression modeling was adopted to measure the comorbidity risk of PN. A total of 3591 patients with PN were identified at the Catholic Medical Center Health System dermatology outpatient clinic in the period 2007–2020. A comparison of the study patients with age- and sex-matched controls (dermatology outpatients without PN) indicated that PN was associated with various comorbidities including chronic kidney disease (adjusted odds ratio (aOR), 1.48; 95% confidence interval (CI), 1.29–1.70), dyslipidemia (aOR, 1.88; 95% CI, 1.56–2.27), type 2 diabetes mellitus (aOR, 1.37; 95% CI, 1.22–1.54), arterial hypertension (aOR, 1.50; 95% CI, 1.30–1.73), autoimmune thyroiditis (aOR, 2.43; 95% CI, 1.42–4.16), non-Hodgkin’s lymphoma (aOR, 1.95; 95% CI, 1.23–3.07), and atopic dermatitis (aOR, 2.16, 95% CI, 1.91–2.45). Regarding prescription patterns, topical steroids were most favored, followed by topical calcineurin inhibitors; oral antihistamines were the most preferred systemic agent for PN. PN is a relatively rare but significant disease among Korean dermatology outpatients with a high comorbidity burden compared to dermatology outpatients without PN. There is great need for breakthroughs in PN treatment.

A Case of Prurigo Nodularis Treating by Acupuncture

Aim

Male, 68 years old, suffering from prurigo nodularis for 7 months, and did not show any significant improvement after oral and topical medications. After 4 months of acupuncture treatment, the NRS for itch scores decreased from 9 to 1; the NRS for sleep scores increased from 5 to 9; HADS decreased from 14 to 2; DLQI decreased from 9 to 5; IGA decreased from 4 to 3. After a 2-month follow-up, the patient was stable in all aspects without new rash.

Conclusion

Acupuncture is a feasible method for the treatment of prurigo nodularis.

Prurigo excoriée treated with low dose naltrexone

A 53-year-old woman presented with a 25-year history of acne excoriée and prurigo excoriée. Her symptoms began in 1988 coinciding with her husband's death from a brain tumour when she was 27. The pruritus affected her quality of life and disturbed her sleep. She had scarring on her face and body resulting from persistent scratching. The pruritus proved refractory to treatment despite a multi-modal treatment approach including multiple topicals, phototherapy and systemic agents such as isotretinoin, antibiotics, anxiolytic agents and neuromodulators. She was extremely frustrated that various treatments had been ineffective at controlling the itch-scratch cycle. She was commenced on low dose naltrexone (LDN), 3 mg nocte, and she became itch free within a few weeks. She reports that the LDN has had a beneficial impact on her quality of life.

Transcriptomic characterization of prurigo nodularis and the therapeutic response to nemolizumab

BACKGROUND

Prurigo nodularis (PN) is a debilitating, difficult-to-treat, intensely pruritic, chronic inflammatory skin disease characterized by hyperkeratotic skin nodules. The pathogenesis of PN is not well understood but is believed to involve cross talk between sensory nerve fibers, immune cells, and the epidermis. It is centered around the neuroimmune cytokine IL-31, driving an intractable itch-scratch cycle.

OBJECTIVE

We sought to provide a comprehensive view of the transcriptomic changes in PN skin and characterize the mechanism of action of the anti-IL-31 receptor inhibitor nemolizumab.

METHOD

RNA sequencing of biopsy samples obtained from a cohort of patients treated with the anti-IL-31 receptor inhibitor nemolizumab and taken at baseline and week 12. Generation and integration of patient data with RNA-Seq data generated from reconstructed human epidermis stimulated with IL-31 and other proinflammatory cytokines.

RESULTS

Our results demonstrate that nemolizumab effectively decreases IL-31 responses in PN skin, leading to effective suppression of downstream inflammatory responses including T_H2/IL-13 and T_H17/IL-17 responses. This is accompanied by decreased keratinocyte proliferation and normalization of epidermal differentiation and function. Furthermore, our results demonstrate how transcriptomic changes associated with nemolizumab treatment correlate with improvement in lesions, pruritus, stabilization of extracellular matrix remodeling, and processes associated with cutaneous nerve function.

CONCLUSION

These data demonstrate a broad response to IL-31 receptor inhibition with nemolizumab and confirm the critical upstream role of IL-31 in PN pathogenesis.

Cluster analysis of circulating plasma biomarkers in prurigo nodularis reveals a distinct systemic inflammatory signature in African Americans

Patients with prurigo nodularis (PN) suffer from intractable itch and dramatic reduction in quality of life. While there is significant clinical heterogeneity in the presentation of PN, disease endotypes remain unknown. We assayed circulating plasma cytokine concentrations in PN patients (n=20) along with matched healthy controls and utilized an unsupervised machine learning algorithm to identify disease endotypes. We found two distinct clusters of PN patients with non-inflammatory (Cluster 1) and inflammatory (Cluster 2) plasma profiles. Cluster 2 had more African-Americans (82%, n=9 vs. 33%, n=3; P=0.028), higher worst-itch numeric rating scale scores (9.5±0.9 vs. 8.3±1.2; P=0.036), and lower quality of life as reflected by higher Dermatology Life Quality Index scores (21.9±6.4 vs. 13.0±4.1; P=0.015). In addition, Cluster 1 had a higher rate of myelopathy (67%, n=6 vs. 18%, n=2; P=0.028). Compared to Cluster 1, Cluster 2 had higher levels of IL-1α, IL-4, IL-5, IL-6, IL-10, IL-17A, IL-22, IL-25, and IFN-α. With population-level analysis, African-American PN patients had higher erythrocyte sedimentation rate, C-reactive protein, ferritin, eosinophils, and lower transferrin than Caucasian PN patients. These findings indicate discrete clusters of PN patients with plasma biomarker profiles corresponding to distinct demographic and clinical characteristics, potentially allowing for precision medicine approaches to treat PN.

Prurigo Nodularis Is Characterized by Systemic and Cutaneous T Helper 22 Immune Polarization

Prurigo nodularis (PN) is an understudied, chronic inflammatory skin disease that disproportionately affects African Americans and presents with intensely pruritic nodules of unknown etiology. To better characterize the immune dysregulation in PN, PBMCs and skin biopsies were obtained from patients with PN and healthy subjects (majority African American) matched by age, race, and sex. Flow cytometric analysis of functional T-cell response comparing patients with PN with healthy subjects identified increased γδT cells (CD3+CD4-CD8-γδTCR+) and Vδ2+ γδT enrichment. Activated T cells demonstrated uniquely increased IL-22 cytokine expression in patients with PN compared with healthy controls. CD4+ and CD8+ T cells were identified as the source of increased circulating IL-22. Consistent with these findings, RNA sequencing of lesional PN skin compared with nonlesional PN skin and biopsy site‒matched control skin demonstrated robust upregulation of T helper (Th) 22‒related genes and signaling networks implicated in impaired epidermal differentiation. Th22‒related cytokine upregulation remained significant, with stratifications by race and biopsy site. Importantly, the expression of the IL-22 receptors IL22RA1 and IL22RA2 was significantly elevated in lesional PN skin. These results indicate that both systemic and cutaneous immune responses in patients with PN are skewed toward a Th22/IL-22 profile. PN may benefit from immunomodulatory therapies directed at Th22‒mediated inflammation.

Therapeutic potential of biologics in prurigo nodularis

INTRODUCTION

Prurigo nodularis (PN) or chronic prurigo of nodular type (CNPG) is a subtype of chronic prurigo with severe pruritus and neuroimmune underlying pathophysiology occurring in a plethora of dermatological, systemic, neurologic, and psychiatric conditions.

AREAS COVERED 

We review the increasing repertoire of biologics in the treatment of CNPG focusing on those targeting interleukins 4, 13, 31, oncostatin M and IgE. Presented information is based on a database research on current clinical trials (clinicaltrials.gov, European Clinical Trials Database (EudraCT), US clinical trial registry ICH-GCP) and a PubMed search for latest publications conducted with the combinations of the terms 'chronic prurigo,' 'prurigo nodularis,' 'pathophysiology,' 'treatment,' 'therapy', and 'biologics.'

EXPERT OPINION

CNPG gets more and more attention as new therapeutic targets have been revealed in recent years, thus allowing the use of targeted approaches. The off-label advent of dupilumab offered advanced insight into the pathogenesis of CNPG and showed an impressive relief of pruritus in the vast majority of patients. New therapies including biologics (e.g. nemolizumab, tralokinumab, lebrikizumab), small molecules (e.g. neurokinin-1 receptor antagonists, janus kinase inhibitors) as well as mu-opioid receptor antagonists and nalbuphine, a μ-antagonist/κ-agonist, are in the pipeline and offer new hope for an improved future patient care.

Cognitive Impairment in Inpatients with Prurigo Nodularis and Psychiatric Comorbidities

BACKGROUND

Prurigo nodularis (PN) is a chronic refractory itchy dermatosis. Although psychiatric comorbidity is known, research in cognitive impairment is lacking. We evaluated the occurrence and types of cognitive impairment in a series of inpatients with PN.

METHODS

This was a retrospective chart review of all the patients with PN admitted to a referral neurological institute from September 2018 to March 2021. Any neurological and psychiatric disorder, along with neuroactive drugs taken, were concomitantly assessed.

RESULTS

A total of 16 patients with PN (median age: 70 years, two males) were selected from a total of 1806 hospital admissions. Most of them had a neurodegenerative cognitive disorder, from mild cognitive impairment (8) to Alzheimer's disease (1), followed by mixed disorder (degenerative and vascular) in six and vascular dementia in one. Comorbid psychiatric diseases (anxiety and depression) were more common than either individual condition, followed by bipolar disorder, whereas two patients did not show psychiatric manifestations. Most patients were on combined treatment with benzodiazepines and antidepressants.

CONCLUSION

Cognitive impairment can be observed in PN. In addition to screening for psychiatric comorbidity and initiating appropriate treatment or referral, clinicians may also consider the presence of cognitive impairment in PN of both degenerative and vascular origin.

Cognitive Impairment in Inpatients with Prurigo Nodularis and Psychiatric Comorbidities

BACKGROUND

Prurigo nodularis (PN) is a chronic refractory itchy dermatosis. Although psychiatric comorbidity is known, research in cognitive impairment is lacking. We evaluated the occurrence and types of cognitive impairment in a series of inpatients with PN.

METHODS

This was a retrospective chart review of all the patients with PN admitted to a referral neurological institute from September 2018 to March 2021. Any neurological and psychiatric disorder, along with neuroactive drugs taken, were concomitantly assessed.

RESULTS

A total of 16 patients with PN (median age: 70 years, two males) were selected from a total of 1806 hospital admissions. Most of them had a neurodegenerative cognitive disorder, from mild cognitive impairment (8) to Alzheimer's disease (1), followed by mixed disorder (degenerative and vascular) in six and vascular dementia in one. Comorbid psychiatric diseases (anxiety and depression) were more common than either individual condition, followed by bipolar disorder, whereas two patients did not show psychiatric manifestations. Most patients were on combined treatment with benzodiazepines and antidepressants.

CONCLUSION

Cognitive impairment can be observed in PN. In addition to screening for psychiatric comorbidity and initiating appropriate treatment or referral, clinicians may also consider the presence of cognitive impairment in PN of both degenerative and vascular origin.

Health-related quality of life and economic burden of prurigo nodularis

BACKGROUND

Prurigo nodularis (PN) is an understudied, pruritic inflammatory skin disease. Little is known about the effect of PN on quality of life and its associated economic burden.

OBJECTIVE

To quantify the impact of PN on quality of life and its economic implications.

METHODS

A cohort study of PN patients (n = 36) was conducted using the Health Utilities Index Mark 3 questionnaire. Control data from US adults (n = 4187) were obtained from the 2002-2003 Joint Canada/United States Survey of Health. Quality-adjusted life year loss and economic costs were estimated by comparing the Health Utilities Index Mark 3 scores of the PN patients with those of the controls.

RESULTS

The PN patients had lower overall health performance compared to the controls, (mean ± SE, 0.52 ± 0.06 vs 0.86 ± 0.003, respectively, P < .001). In multivariable regression, PN was found to be associated with worse health performance (coefficient -0.34, 95% CI [-0.46 to -0.23]), most prominent in the pain subdomain (coefficient -0.24, 95% CI [-0.35 to -0.13]). This correlated to an average of 6.5 lifetime quality-adjusted life years lost per patient, translating to an individual lifetime economic burden of $323,292 and a societal burden of $38.8 billion.

CONCLUSION

These results demonstrate that PN is associated with significant quality-of-life impairment, similar to the level of other chronic systemic conditions. PN is also associated with a substantial individual economic burden, emphasizing the necessity of research on effective treatment options.

Clinical characteristics and disease burden in prurigo nodularis

BACKGROUND

Prurigo nodularis (PN) is a chronic inflammatory skin disease characterized by intense pruritus, but information on patient experience and impact on quality of life (QoL) remains understudied.

AIM

To characterize disease characteristics and QoL in a global sample of patients with PN.

METHODS

An anonymous survey was distributed via patient support groups for PN.

RESULTS

In total, 231 members responded to the survey. The majority of respondents reported itch localized both to nodules and to intervening skin (67.0%). Associated symptoms included prickling, pain, stinging and burning. The extensor lower legs (69% right, 67.3% left) and flexor forearms (66.1% right, 62% left) were the most common sites of itch. Participants reported frequent healthcare utilization, with 36.3% visiting a doctor ≥ 10 times in the past year. Physician-diagnosed anxiety (45.4%), depression (16.4%) and the atopic triad (18.7%) were commonly reported. Patients with PN had mean scores of 16.4, 11.6 and 16.8 on the Dermatology Life Quality Index, Pittsburgh Sleep Quality Index and 5-Dimensions Itch, respectively.

CONCLUSIONS

Severe pruritus with accompanying pain, stinging and burning is characteristic of PN, with the majority of patients experiencing itch in both nodular and interlesional skin. Patients further report decreased QoL scores and impaired sleep. Patient experiences should guide future management of PN.

Association of prurigo nodularis and infectious disease hospitalizations: a national cross-sectional study

BACKGROUND

Prurigo nodularis (PN) is associated with a variety of systemic comorbidities, including infectious diseases such as HIV and viral hepatitis. There are limited data on other infectious disease comorbidities in patients with PN.

AIM

To characterize infectious disease hospitalizations among patients with PN and the associated cost burden.

METHODS

We searched the 2016-2017 National Inpatient Sample, a cross-sectional sample of 20% of all US hospitalizations, for infectious disease hospitalizations among patients with PN. Associations of PN with infections and related costs were determined using multivariable logistic and linear regression, adjusting for age, race, sex and insurance type.

RESULTS

PN was associated with any infection overall (OR = 2.98, 95% CI 2.49-3.56), and with HIV, cutaneous, hepatobiliary, central nervous system, bacterial, viral and fungal/parasitic infections and for sepsis. Patients with PN had a higher mean cost of care (US$11 667 vs. US$8893, P < 0.001) and length of stay (5.5 vs. 4.2 days, P < 0.001) for any infection overall and for 7 of 13 other infections. Adjusting for age, race, sex and insurance coverage, PN was associated with higher cost (+30%, 95% CI +17 to +44%) and higher length of stay (+30%, 95% CI +18 to +44%) for any infection overall, and for several specific infections. These associations remained with alternate regression models adjusting for severity of illness.

CONCLUSION

There is a high infectious disease burden among patients with PN, corresponding to higher healthcare utilization and spending. Clinicians must be aware of these associations when treating these patients with immunomodulatory drugs.

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.