Efficacy and safety of nemolizumab and topical corticosteroids for prurigo nodularis: Results from a randomised, double-blind, placebo-controlled, phase II/III clinical study in patients aged ≥13 years.

BACKGROUND: Prurigo nodularis, a chronic inflammatory skin condition, adversely affects the quality of life of affected individuals. Current treatment options for prurigo nodularis in Japan are limited. OBJECTIVES: To evaluate the optimal dose, efficacy, and safety of long-term treatment with nemolizumab in patients with prurigo nodularis in Japan. METHODS: In a 16-week, double-blind, phase II/III study, patients aged ≥13 years with prurigo nodularis were randomly assigned (1:1:1) to nemolizumab 30 mg, 60 mg, or placebo groups, with concomitant topical corticosteroids, every 4 weeks. The primary efficacy end point was the percentage change in the weekly mean Peak Pruritus Numerical Rating Scale (PP-NRS) score (range, 0 to 10, with higher scores indicating worse itching) from baseline to week 16. Secondary efficacy end points assessed the impact of treatment on pruritus, prurigo nodularis severity, sleep, and quality of life. RESULTS: At week 16, the least-squares mean percentage change from baseline in the PP-NRS score was -61·1% in the nemolizumab 30 mg group (n = 77), -56·0% in the 60 mg group (n = 76), and -18·6% in the placebo group (n = 76). Differences between both nemolizumab groups and placebo were significant; the difference between the 30 mg and placebo groups was -42·5% (95% confidence interval [CI], -51·9 to -33·1; P<0·0001), and between the 60 mg and placebo groups was -37·4% (95% CI, -46·7 to -28·1; P<0·0001). Nemolizumab-treated patients also had greater improvements in the number and severity of prurigo nodules, and in sleep and quality of life compared with the placebo group. Both nemolizumab doses were well tolerated. CONCLUSIONS: Improvements in prurigo nodularis were greater following nemolizumab treatment, despite continuation of topical corticosteroids in both groups. (Funded by Maruho; jRCT number, 2011200017.).

Activated Akt expression is associated with the recurrence of primary melanomas and further refines the prognostic and predictive values for relapse in acral melanomas.

A PTEN deficiency leads to the activation of phospho-Akt at serine 473 (p-Akt) and promotes the tumorigenesis of melanomas by coupling with NUAK2 amplification. We tested the prognostic impact of p-Akt and/or NUAK2 expression on the relapse-free survival (RFS) and overall survival (OS) of melanoma patients. Primary tumors from patients with acral melanomas (112), Low-cumulative sun damage (CSD) melanomas (38), and High-CSD melanomas (18) were examined using immunohistochemistry and their prognostic significance was analyzed statistically. The expression of p-Akt was found in 32.1%, 68.4%, and 55.6% of acral, Low-CSD, and High-CSD melanomas, while NUAK2 expression was found in 46.4%, 76.3%, and 50.0%, respectively. Either p-Akt or NUAK2 expression was inversely correlated with the RFS of primary melanoma patients and acral melanoma patients (p-Akt: p < .0001, p < .0001; NUAK2; p = .0005, p < .0001, respectively). Strikingly, multivariate analyses revealed that p-Akt had a significant impact on RFS (Hazard ratio = 4.454; p < .0001), while NUAK2 did not. Further subset analyses revealed that p-Akt expression had an inferior RFS of patients with acral melanomas (Hazard ratio = 4.036; p = .0005). We conclude that the expression of p-Akt has a significant impact on RFS of patients with primary melanomas and can predict the relapse of patients with acral melanomas.

Cutaneous basophil infiltration in atopic dermatitis is associated with abundant epidermal infiltration of helper T cells: A preliminary retrospective study.

Atopic dermatitis (AD) is a heterogenous inflammatory skin disorder. Our previous study revealed that basophil infiltration in skin is observed in approximately 60% of AD cases. However, the clinical and histological characteristics of AD associated with basophil infiltration remain unclear. We examined basophil infiltration by immunohistochemical staining of 38 specimens from 34 patients who underwent skin biopsies to diagnose AD from April 2016 to September 2021 at Tokyo Medical and Dental University Hospital. The patients/specimens were divided into two groups, 17 patients/21 specimens associated with little or no basophil infiltration (basophil-low group) and 17 patients/17 specimens associated with marked basophil infiltration (basophil-high group). The clinical characteristics of the patients (age, sex, complications, blood biomarkers, skin symptoms, and treatment) and histological features of the specimens were compared between the groups. Basophil-high patients were significantly younger than basophil-low patients. Blood basophil counts were higher in basophil-high patients than in basophil-low patients. CD4+ T-cell infiltration was more marked in basophil-high specimens than in basophil-low specimens. CD4+ T cells infiltrated into the dermis as well as into the epidermis only in the basophil-high specimens. Thus, basophil-high AD can be characterized by skin lesions associated with abundant helper T-cell infiltration in younger patients.

Long-term evaluation of the safety and efficacy of a novel 20% oxybutynin hydrochloride lotion for primary palmar hyperhidrosis: An open-label extension study.

The long-term safety and efficacy of 52-week application of oxybutynin hydrochloride 20% lotion (20% OL) for the treatment of primary palmar hyperhidrosis (PPHH) in Japanese patients aged ≥12 years were evaluated in an open-label extension (OLE) of a 4-week, randomized, double-blind (DB) study. The OLE included 114 patients who completed the DB study and wished to continue treatment and 12 new patients. In the safety analysis population (125 patients), the incidence of adverse events (AEs) and adverse drug reactions (ADRs) was 79.2% and 36.0%, respectively. Serious AEs were observed in two patients but were considered unrelated to the investigational drug. The incidence of AEs that led to study discontinuation was 1.6%. The incidence of application site AEs and ADRs was 35.2% and 26.4%, respectively. The severity of most events was mild. The incidence of anticholinergic AEs related to dry mouth was 3.2% for thirst and 0.8% for dry throat. The long-term efficacy of 20% OL was confirmed by a long-lasting reduction in sweat volume and improvement in the Hyperhidrosis Disease Severity Scale and Dermatology Life Quality Index. This study has several limitations: First the results may include some bias because most of the participants were from the prior DB study; second, the results may not be generalizable because only a few participants were in the age group most susceptible to PPHH (i.e., < 15 years old); and third, the study did not obtain safety information from treatment for more than 52 weeks, so this information must be collected in clinical practice in the future. No reduced therapeutic effect was observed in patients with PPHH in this study after 52-week application of 20% OL. Also, few patients experienced serious AEs or AEs that led to study treatment discontinuation.

A novel lotion formulation of 20% oxybutynin hydrochloride for the treatment of primary palmar hyperhidrosis: A randomized, placebo-controlled, double-blind, phase III study.

BACKGROUND: No previous controlled studies have been specifically designed or adequately powered to show the efficacy of topical oxybutynin for palmar hyperhidrosis by using quantitative measures. OBJECTIVE: To evaluate efficacy of 20% oxybutynin hydrochloride lotion (20% OL) in reducing palmar sweat volume in patients with primary palmar hyperhidrosis (PPHH). METHODS: In a randomized controlled trial, Japanese patients with PPHH aged 12 years and older received either 20% OL (n = 144) or placebo (n = 140) on both palms once daily for 4 weeks. Palmar sweat volume was measured by the ventilated capsule method. For the primary outcome, response was defined as a reduction of sweat volume of at least 50% from baseline. RESULTS: At week 4, the responder rate for sweat volume was significantly higher in the 20% OL arm than in the placebo arm (52.8% vs 24.3%, respectively; treatment difference, 28.5% [95% CI, 17.7% to 39.3%]; P < .001). No serious adverse events occurred, and no adverse events led to treatment discontinuation. LIMITATIONS: The treatment period was only 4 weeks. CONCLUSIONS: In patients with PPHH, 20% OL is superior to placebo in reducing palmar sweat volume.

Efficacy and safety of omalizumab in adult patients with wheat-dependent exercise-induced anaphylaxis: Reduction of in vitro basophil activation and allergic reaction to wheat.

BACKGROUND: In patients with wheat-dependent exercise-induced anaphylaxis (WDEIA), anaphylactic shock occurs frequently, therefore avoidance of wheat products is recommended. We aimed to evaluate efficacy and safety of long-term omalizumab treatment for adult patients with WDEIA. METHODS: In this phase 2, multicentre single-arm trial, 20 adult patients with WDEIA were enrolled (UMIN 000019250). All patients were administered 150-600 mg of omalizumab subcutaneously and evaluations (basophil activation and blood examination) were performed at regular intervals during administration period (0-48 weeks) and observation period (48-68 weeks). Primary endpoint was proportion of the patients who achieved a basophil activation rate below 10% with fractionated wheat preparations, and secondary endpoint was proportion of the patients with no allergic reactions after wheat products ingestion. RESULTS: During the omalizumab treatment, more than 80% of the patients achieved the basophil activation rate less than 10% against all fractionated wheat preparations, and 68.8% of the patients who achieved the primary endpoint experienced no allergic reaction. During the observation period, the proportion of the patients who achieved a basophil activation rate below 10% decreased gradually, and the proportion of patients with positive allergic reactions increased gradually thereafter and reached maximum of 46.7%. Severe adverse events were not observed during the study. CONCLUSIONS: Long-term omalizumab treatment is safe and effective for adult patients with WDEIA when assessed by basophil activation rate with wheat allergens as well as allergic reactions after lifting of restrictions on wheat intake. However, this is not enough to achieve desensitization.

IL-31-generating network in atopic dermatitis comprising macrophages, basophils, thymic stromal lymphopoietin, and periostin.

BACKGROUND: IL-31 is a type 2 cytokine involved in the itch sensation in atopic dermatitis (AD). The cellular origins of IL-31 are generally considered to be TH2 cells. Macrophages have also been implicated as cellular sources of IL-31. OBJECTIVE: We sought to determine the expression of IL-31 by macrophages and to elucidate the productive mechanisms and contributions to itch in AD skin lesions. METHODS: Expression of IL-31 by macrophages, expressions of thymic stromal lymphopoietin (TSLP) and periostin, and presence of infiltrating basophils in human AD lesions were examined through immunofluorescent staining, and correlations were assessed. Furthermore, mechanisms of inducing IL-31-expressing macrophages were analyzed in an MC903-induced murine model for AD in vivo and in mouse peritoneal macrophages ex vivo. RESULTS: A significant population of IL-31+ cells in human AD lesions was that of CD68+ cells expressing CD163, an M2 macrophage marker. The number of IL-31+/CD68+ cells correlated with epidermal TSLP, dermal periostin, and the number of dermal-infiltrating basophils. In the MC903-induced murine AD model, significant scratching behaviors with enhanced expressions of TSLP and periostin were observed, accompanied by massive infiltration of basophils and IL-31+/MOMA-2+/Arg-1+ cells. Blockade of IL-31 signaling with anti-IL-31RA antibody or direct depletion of macrophages by clodronate resulted in attenuation of scratching behaviors. To effectively reduce lesional IL-31+ macrophages and itch, basophil depletion was essential in combination with TSLP- and periostin-signal blocking. Murine peritoneal macrophages produced IL-31 when stimulated with TSLP, periostin, and basophils. CONCLUSIONS: A network comprising IL-31-expressing macrophages, TSLP, periostin, and basophils plays a significant role in AD itch.

Cohort study of subclinical sensitization against galactose-α-1,3-galactose in Japan: Prevalence and regional variations.

Sensitization to galactose-α-1,3-galactose (α-Gal) leads to the development of α-Gal syndrome, which includes red meat allergy and cetuximab-induced anaphylaxis. Since tick bites represent the main cause of α-Gal sensitization, it was speculated that sensitization to α-Gal occurs throughout Japan. However, few cohort studies have investigated α-Gal sensitization in Japan. Therefore, we aimed to elucidate the subclinical sensitization rate to α-Gal in Japan. Sera were obtained from 300 participants without food or cetuximab allergy at Shimane University Hospital (Shimane prefecture), Tokyo Medical and Dental University Hospital (Tokyo metropolis), and Tohoku University Hospital (Miyagi prefecture). ImmunoCAP-bovine thyroglobulin (BTG), ImmunoCAP-beef, and IgE immunoblotting with cetuximab were performed to detect α-Gal-specific IgE. Clinical information was collected from participants using a questionnaire. The overall positivity rate of ImmunoCAP-BTG was 4.0% without significant inter-institute differences, whereas that for ImmunoCAP-beef was 9.7% with a significant inter-institute difference. Tokyo Medical and Dental University Hospital (19.0%) had the highest positivity rate. The positivity rate based on cetuximab IgE immunoblotting was 2.7%, without any significant inter-institute differences. The overall positivity rate for both ImmunoCAP-BTG and cetuximab immunoblotting was 2.0%, with a significant inter-institute difference; 5.0% of Shimane University Hospital was the highest. Two cases showed sensitization against the non-α-Gal epitope of cetuximab. The overall positivity rate for both ImmunoCAP-beef and cetuximab immunoblotting was 1.3%, without significant inter-institute differences. Male sex was associated with positive beef-specific IgE. The prevalence of subclinical sensitization to α-Gal is estimated at 2.0%-4.0% in Japan and may be higher in rural areas, supporting an association between tick bites and α-Gal sensitization. In contrast, the prevalence of subclinical sensitization to beef is 9.7% in Japan and is highest in Tokyo Metropolis, suggesting the presence of another IgE-binding epitope apart from α-Gal and another sensitization route in the sensitization to beef IgE.

An epidemiological survey of anhidrotic/hypohidrotic ectodermal dysplasia in Japan: High prevalence of allergic diseases.

Anhidrotic/hypohidrotic ectodermal dysplasia (A/HED) is a congenital disorder characterized by anhidrosis/hypohidrosis and inadequate hair and dental dysplasia. Large-scale case studies of patients with A/HED have already been conducted overseas, while there has been no large-scale study, but only a few case reports in Japan. Furthermore, an epidemiological study of this disease has not been conducted in Japan to date. The purpose of this study was to investigate the clinical characteristics of A/HED patients, the status of genetic aberrations and complications of A/HED in Japan. Initially, we conducted a physician-initiated questionnaire survey of A/HED patients who visited medical institutions across Japan to investigate their backgrounds, clinical symptoms, genotypes, diagnostic methods and complications of A/HED. We also investigated the presence or absence of various allergic diseases (atopic dermatitis-like skin manifestations, bronchial asthma and food allergies). Questionnaires were also obtained from 26 patients with ectodermal dysplasia (ED) who visited four medical institutions. We compared the incidence of allergic diseases in healthy controls in a similar study to that of patients. Twenty-four of those patients were considered to have A/HED, of which 18 had a confirmed genetic diagnosis and were genotyped. All patients had anhidrosis or hypohidrosis, hair and dental dysplasia, and unique facial appearance; 23 patients had several cutaneous manifestations and seven patients had periorbital pigmentation. In addition, there was a significantly higher incidence of atopic dermatitis-like cutaneous manifestations, bronchial asthma and food allergies in the A/HED patients than in healthy controls. We report the results from a questionnaire survey of 24 patients with A/HED. This is the first report of a large number of A/HED patients in Japan. This study clarifies the status of clinical diagnosis and genetic testing of A/HED patients in Japan, as well as the characteristics of their skin symptoms and allergic complications.

Topical glycopyrronium tosylate in Japanese patients with primary axillary hyperhidrosis: A randomized, double-blind, vehicle-controlled study.

Glycopyrronium tosylate cloth, an anticholinergic drug, has been approved for the topical treatment of primary axillary hyperhidrosis in the USA, but its effects in Japanese patients have not been previously investigated. This 4-week, randomized, double-blind, vehicle-controlled, multicenter study was conducted to evaluate the efficacy and safety of glycopyrronium tosylate cloth for primary axillary hyperhidrosis patients in Japan. Eligible patients, who were ≥9 years of age and had primary axillary hyperhidrosis ≥6 months, with gravimetrically-measured sweat production ≥50 mg/5 min, and Hyperhidrosis Disease Severity Scale ≥3 (moderate) were randomized 1:1:1 to once daily topical glycopyrronium tosylate 3.75%, 2.5%, or vehicle. Overall, 497 patients (163 in the glycopyrronium tosylate 3.75% group, 168 in the glycopyrronium tosylate 2.5% group, and 166 in the vehicle group, hereinafter in this order) were randomized. Statistically higher proportions of patients in the glycopyrronium tosylate groups achieved ≥2-point improvement in Hyperhidrosis Disease Severity Scale and ≥50% reduction in sweat production from baseline versus vehicle at week 4 (51.6%, 41.1%, and 16.4%, respectively; p < 0.001 in both cases). Higher responder rates in the glycopyrronium tosylate groups compared with the vehicle group occurred as early as week 1. The most common treatment-emergent adverse events in patients treated with glycopyrronium tosylate were photophobia, mydriasis, thirst, and dysuria. Most treatment-emergent adverse events were mild as determined by the investigators. The incidence of treatment-emergent adverse events leading to treatment modification was low in the three groups. The 4-week use of topical glycopyrronium tosylate improved the patient-reported outcome measure Hyperhidrosis Disease Severity Scale and objectively-evaluated sweat production with a favorable benefit/risk profile.

Epicutaneous challenge with protease allergen requires its protease activity to recall TH2 and TH17/TH22 responses in mice pre-sensitized via distant skin.

Epicutaneous exposure to allergenic proteins is an important sensitization route for skin diseases like protein contact dermatitis, immunologic contact urticaria, and atopic dermatitis. Environmental allergen sources such as house dust mites contain proteases, which are frequent allergens themselves. Here, the dependency of T-helper (TH) cell recall responses on allergen protease activity in the elicitation phase in mice pre-sensitized via distant skin was investigated. Repeated epicutaneous administration of a model protease allergen, i.e. papain, to the back skin of hairless mice induced skin inflammation, serum papain-specific IgE and TH2 and TH17 cytokine responses in the sensitization sites, and antigen-restimulated draining lymph node cells. In the papain-sensitized but not vehicle-treated mice, subsequent single challenge on the ear skin with papain, but not with protease inhibitor-treated papain, up-regulated the gene expression of TH2 and TH17/TH22 cytokines along with cytokines promoting these TH cytokine responses (TSLP, IL-33, IL-17C, and IL-23p19). Up-regulation of IL-17A gene expression and cells expressing RORγt occurred in the ear skin of the presensitized mice even before the challenge. In a reconstructed epidermal model with a three-dimensional culture of human keratinocytes, papain but not protease inhibitor-treated papain exhibited increasing transdermal permeability and stimulating the gene expression of TSLP, IL-17C, and IL-23p19. This study demonstrated that allergen protease activity contributed to the onset of cutaneous TH2 and TH17/TH22 recall responses on allergen re-encounter at sites distant from the original epicutaneous sensitization exposures. This finding suggested the contribution of protease-dependent barrier disruption and induction of keratinocyte-derived cytokines to the recall responses.

Stem cell spreading dynamics intrinsically differentiate acral melanomas from nevi.

Early differential diagnosis between malignant and benign tumors and their underlying intrinsic differences are the most critical issues for life-threatening cancers. To study whether human acral melanomas, deadly cancers that occur on non-hair-bearing skin, have distinct origins that underlie their invasive capability, we develop fate-tracing technologies of melanocyte stem cells in sweat glands (glandular McSCs) and in melanoma models in mice and compare the cellular dynamics with human melanoma. Herein, we report that glandular McSCs self-renew to expand their migratory progeny in response to genotoxic stress and trauma to generate invasive melanomas in mice that mimic human acral melanomas. The analysis of melanocytic lesions in human volar skin reveals that genetically unstable McSCs expand in sweat glands and in the surrounding epidermis in melanomas but not in nevi. The detection of such cell spreading dynamics provides an innovative method for an early differential diagnosis of acral melanomas from nevi.

Cost-of-illness study for axillary hyperhidrosis in Japan.

The prevalence of primary axillary hyperhidrosis in Japan is 5.75% (males, 6.60%; females, 4.72%) in the population aged 5-64 years. No study on comprehensively evaluated direct medical costs, hygiene product costs, and productivity loss in axillary hyperhidrosis patients has been published in Japan. The aim of this study was to estimate the cost of illness for axillary hyperhidrosis in Japan by conducting a nationwide insurance claims database analysis and a cross-sectional Web-based survey. Among patients diagnosed with primary axillary hyperhidrosis at least once between November 2012 and October 2019, health insurance receipt data of 1447 patients were analyzed. A cross-sectional Web-based survey was conducted on 321 patients aged 16-59 years with axillary hyperhidrosis to calculate hygiene product costs and productivity loss using a Work Productivity and Activity Impairment questionnaire. Furthermore, nationwide estimation was performed for the hygiene product costs and productivity loss based on the number of patients estimated from the prevalence. The annual direct medical costs per axillary hyperhidrosis patient were ¥91 491 in 2016, ¥93 155 in 2017, and ¥75 036 in 2018. In all of these years, botulinum toxin type A injection accounted for approximately 90% of the total costs. The annual total cost of hygiene products per axillary hyperhidrosis patient was ¥9325. The overall work impairment (%) of working patients with axillary hyperhidrosis was 30.52%, and its monthly productivity loss was ¥120 593/patient. The activity impairment (%) of full-time housewives with axillary hyperhidrosis was 49.05% and its monthly productivity loss was ¥176 368/patient. The annual hygiene product cost based on the nationwide estimation was ¥24.5 billion and the monthly productivity loss was ¥312 billion. The significant cost associated with axillary hyperhidrosis was clarified. If out-of-pocket expenses for treatments not covered by health insurance are included in the estimation, the cost will further increase.

Genome-wide association study reveals an association between the HLA-DPB1∗02:01:02 allele and wheat-dependent exercise-induced anaphylaxis.

Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a life-threatening food allergy triggered by wheat in combination with the second factor such as exercise. The identification of potential genetic risk factors for this allergy might help high-risk individuals before consuming wheat-containing food. We aimed to identify genetic variants associated with WDEIA. A genome-wide association study was conducted in a discovery set of 77 individuals with WDEIA and 924 control subjects via three genetic models. The associations were confirmed in a replication set of 91 affected individuals and 435 control individuals. Summary statistics from the combined set were analyzed by meta-analysis with a random-effect model. In the discovery set, a locus on chromosome 6, rs9277630, was associated with WDEIA in the dominant model (OR = 3.95 [95% CI, 2.31-6.73], p = 7.87 × 10-8). The HLA-DPB1∗02:01:02 allele displayed the most significant association with WDEIA (OR = 4.51 [95% CI, 2.66-7.63], p = 2.28 × 10-9), as determined via HLA imputation following targeted sequencing. The association of the allele with WDEIA was confirmed in replication samples (OR = 3.82 [95% CI, 2.33-6.26], p = 3.03 × 10-8). A meta-analysis performed in the combined set revealed that the HLA-DPB1∗02:01:02 allele was significantly associated with an increased risk of WDEIA (OR = 4.13 [95% CI, 2.89-5.93], p = 1.06 × 10-14). Individuals carrying the HLA-DPB1∗02:01:02 allele have a significantly increased risk of WDEIA. Further validation of these findings in independent multiethnic cohorts is needed.

Recurrent Auricular Pseudocyst: Successful Treatment Using a Dental Silicon Cast.

Auricular pseudocysts (APs) are benign intercartilaginous cysts at the auricle. Various therapeutic options have been used to treat APs, but they frequently recur in usual clinical practice. Here, we report a case of AP successfully treated using a silicon cast. A 65-year-old male presented with a cyst on his right auricle. Although a local injection of steroid was administered, the cyst had recurred. A dental silicon cast was applied after removal of the contents of the cyst by suction. There was no recurrence of the cyst 6 years after that treatment. Dental silicon casts are a novel technique for an appropriate fixation over auricles in the treatment of APs and had an effective therapeutic result in our case.

Supraclavicular Scrofuloderma: A Diagnostic Challenge without Apparent Clinical Manifestations of Tuberculosis.

Scrofuloderma is one of the cutaneous manifestations of tuberculosis and usually occurs when underlying tuberculosis such as lymphadenitis directly involves the skin. However, the diagnosis of scrofuloderma without other apparent clinical manifestations of tuberculosis is sometimes challenging. A 27-year-old male from Bangladesh presented with a dome-shaped tumor on his right clavicle. MRI showed a high-density area that expanded from the lymph nodes between the internal jugular vein and the common carotid artery into the tumor on his right clavicle. Bacterial examinations of cultures from the tumor detected Mycobacterium tuberculosis. Further examinations for pulmonary tuberculosis including chest X-ray and computed tomography did not detect any lesions suggestive of pulmonary tuberculosis. From those examinations, the diagnosis of scrofuloderma was made. We emphasize the importance of recognizing a variety of clinical manifestations of tuberculosis including scrofuloderma due to the recent increase of immigrants from developing countries.

2020 guidelines for the diagnosis and treatment of prurigo.

Prurigo is a treatment-resistant skin disease characterized by multiple isolated papules/nodules that cause severe itch. Prurigo papules/nodules occur either as primary lesions or as secondary lesions due to persistent scratching. The fundamental concepts and classifications of prurigo have not been sufficiently established, and considerable confusion remains regarding this topic. Clinical guidelines for chronic prurigo in Japan were published in 2012 in an attempt to reduce confusion regarding the concepts of prurigo and to standardize laboratory tests and treatments. However, the diagnostic terms for prurigo and associated concepts have changed over time, and new forms of treatment are under development. We have, thus, updated and revised the guidelines to classify prurigo based on clinical forms and causes, and disease name classifications based on the clinical form have been further simplified, such as prurigo nodularis, prurigo chronica multiformis, and prurigo (not otherwise specified). Expressions for acute, subacute, and chronic forms are not used. These guidelines outline the current concepts and specify treatments for prurigo.