IL36RN mutations define a severe autoinflammatory phenotype of generalized pustular psoriasis

International Consensus Definition and Diagnostic Criteria for Generalized Pustular Psoriasis From the International Psoriasis Council

Importance

Generalized pustular psoriasis (GPP) lacks internationally accepted definitions and diagnostic criteria, impeding timely diagnosis and treatment and hindering cross-regional clinical and epidemiological study comparisons.

Objective

To develop an international consensus definition and diagnostic criteria for GPP using the modified Delphi method.

Evidence Review

The rarity of GPP presents a challenge in acquiring comprehensive published clinical data necessary for developing standardized definition and criteria. Instead of relying on a literature search, 43 statements that comprehensively addressed the fundamental aspects of the definitions and diagnostic criteria for GPP were formulated based on expert reviews of 64 challenging GPP cases. These statements were presented to a panel of 33 global GPP experts for voting, discussion, and refinements in 2 virtual consensus meetings. Consensus during voting was defined as at least 80% agreement; the definition and diagnostic criteria were accepted by all panelists after voting and in-depth discussion.

Findings

In the first and second modified Delphi round, 30 (91%) and 25 (76%) experts participated. In the initial Delphi round, consensus was achieved for 53% of the statements, leading to the approval of 23 statements that were utilized to develop the proposed definitions and diagnostic criteria for GPP. During the second Delphi round, the final definition established was, "Generalized Pustular Psoriasis is a systemic inflammatory disease characterized by cutaneous erythema and macroscopically visible sterile pustules." It can occur with or without systemic symptoms, other psoriasis types, and laboratory abnormalities. GPP may manifest as an acute form with widespread pustules or a subacute variant with an annular phenotype. The identified essential criterion was, "Macroscopically visible sterile pustules on erythematous base and not restricted to the acral region or within psoriatic plaques."

Conclusions and Relevance

The achievement of international consensus on the definition and diagnostic criteria for GPP underscores the importance of collaboration, innovative methodology, and expert engagement to address rare diseases. Although further validation is needed, these criteria can serve as a reference point for clinicians, researchers, and patients, which may contribute to more accurate diagnosis and improved management of GPP.

A genome-wide meta-analysis of palmoplantar pustulosis implicates TH2 responses and cigarette smoking in disease pathogenesis

BACKGROUND

Palmoplantar pustulosis (PPP) is an inflammatory skin disorder that mostly affects smokers and manifests with painful pustular eruptions on the palms and soles. Although the disease can present with concurrent plaque psoriasis, TNF and IL-17/IL-23 inhibitors show limited efficacy. There is therefore a pressing need to uncover PPP disease drivers and therapeutic targets.

OBJECTIVES

We sought to identify genetic determinants of PPP and investigate whether cigarette smoking contributes to disease pathogenesis.

METHODS

We performed a genome-wide association meta-analysis of 3 North-European cohorts (n = 1,456 PPP cases and 402,050 controls). We then used the scGWAS program to investigate the cell-type specificity of the association signals. We also undertook genetic correlation analyses to examine the similarities between PPP and other immune-mediated diseases. Finally, we applied Mendelian randomization to analyze the causal relationship between cigarette smoking and PPP.

RESULTS

We found that PPP is not associated with the main genetic determinants of plaque psoriasis. Conversely, we identified genome-wide significant associations with the FCGR3A/FCGR3B and CCHCR1 loci. We also observed 13 suggestive (P < 5 × 10-6) susceptibility regions, including the IL4/IL13 interval. Accordingly, we demonstrated a significant genetic correlation between PPP and TH2-mediated diseases such as atopic dermatitis and ulcerative colitis. We also found that genes mapping to PPP-associated intervals were preferentially expressed in dendritic cells and often implicated in T-cell activation pathways. Finally, we undertook a Mendelian randomization analysis, which supported a causal role of cigarette smoking in PPP.

CONCLUSIONS

The first genome-wide association study of PPP points to a pathogenic role for deregulated TH2 responses and cigarette smoking.

The role of interleukin-36 in health and disease states

The interleukin (IL)-1 superfamily upregulates immune responses and maintains homeostasis between the innate and adaptive immune systems. Within the IL-1 superfamily, IL-36 plays a pivotal role in both innate and adaptive immune responses. Of the four IL-36 isoforms, three have agonist activity (IL-36α, IL-36β, IL-36γ) and the fourth has antagonist activity (IL-36 receptor antagonist [IL-36Ra]). All IL-36 isoforms bind to the IL-36 receptor (IL-36R). Binding of IL-36α/β/γ to the IL-36R recruits the IL-1 receptor accessory protein (IL-1RAcP) and activates downstream signalling pathways mediated by nuclear transcription factor kappa B and mitogen-activated protein kinase signalling pathways. Antagonist binding of IL-36Ra to IL-36R inhibits recruitment of IL-1RAcP, blocking downstream signalling pathways. Changes in the balance within the IL-36 cytokine family can lead to uncontrolled inflammatory responses throughout the body. As such, IL-36 has been implicated in numerous inflammatory diseases, notably a type of pustular psoriasis called generalized pustular psoriasis (GPP), a chronic, rare, potentially life-threatening, multisystemic skin disease characterised by recurrent fever and extensive sterile pustules. In GPP, IL-36 is central to disease pathogenesis, and the prevention of IL-36-mediated signalling can improve clinical outcomes. In this review, we summarize the literature describing the biological functions of the IL-36 pathway. We also consider the evidence for uncontrolled activation of the IL-36 pathway in a wide range of skin (e.g., plaque psoriasis, pustular psoriasis, hidradenitis suppurativa, acne, Netherton syndrome, atopic dermatitis and pyoderma gangrenosum), lung (e.g., idiopathic pulmonary fibrosis), gut (e.g., intestinal fibrosis, inflammatory bowel disease and Hirschsprung's disease), kidney (e.g., renal tubulointerstitial lesions) and infectious diseases caused by a variety of pathogens (e.g., COVID-19; Mycobacterium tuberculosis, Pseudomonas aeruginosa, Streptococcus pneumoniae infections), as well as in cancer. We also consider how targeting the IL-36 signalling pathway could be used in treating inflammatory disease states.

Comparison of metabolic and neurological comorbidities in Asian patients with psoriasis and atopic dermatitis

Although various comorbidities have been noted to be associated with atopic dermatitis (AD) and psoriasis, few studies have compared comorbidities between the two diseases, and little is known about whether these comorbidities vary by the subtypes of psoriasis. In this study of 1:1 age- and sex-matched pair analysis between patients diagnosed with either psoriasis or AD at Asan Medical Center between 1991 and 2020, comorbidities, as determined by the International Classification of Diseases-10 codes, and likelihood ratios of metabolic and neurologic comorbidities in psoriasis compared with AD were studied using a logistic regression model. Among a total of 14,128 patients, the psoriasis group had higher odds of obesity (odds ratio [95% confidence interval]: 1.49 [1.34-1.66]), hypertension (1.14 [1.03-1.26]), diabetes mellitus (1.46 [1.29-1.66]), chronic kidney disease (1.59 [1.22-2.08]), and Parkinson's disease (2.1 [1.15-3.83]) than the AD group. Subgroup analysis revealed that patients with plaque psoriasis had higher odds of obesity (1.18 [1.05-1.33]), hypertension (1.18 [1.06-1.32]), diabetes mellitus (1.53 [1.34-1.75]), chronic kidney disease (1.66 [1.26-2.17]), and Parkinson's disease (2.12 [1.16-3.88]) compared with AD. Meanwhile, guttate psoriasis was associated with higher odds of dementia (3.63 [1.06-12.40]) and patients with generalized pustular psoriasis showed higher odds of diabetes mellitus (5.42 [1.56-18.83]) compared with AD. In conclusion, Asian patients with all types of psoriasis should be closely monitored for the development of metabolic and neurologic diseases, especially men and those aged ≥ 40 years.

Clinical and Disease Burden of Patients with Generalized Pustular Psoriasis: A Review of Real-World Evidence

Generalized pustular psoriasis (GPP) is a chronic, rare, and potentially life-threatening disease. There is limited understanding of patient characteristics in GPP and their correlation with disease progression or healthcare resource utilization. Our review aims to examine real-world evidence on these characteristics and the associated disease burden as related to economic and quality of life factors. Results showed that most patients with GPP experienced flares once a year, lasting from 2 weeks to 3 months, with > 80% of patients having residual disease post-flare, with/without treatment, indicating the long-term nature of GPP. The impact of GPP on patients' daily activities was significant, even in the absence of a flare. GPP adversely affected mental health, and anxiety and depression were reported regularly. Patients with GPP had more comorbidities, were prescribed more medication, and had more inpatient and outpatient visits than in matched plaque psoriasis or general population cohorts. Improving the education of healthcare providers in diagnosing GPP, defining disease flares, and managing the disease, as well as making globally accepted clinical guidelines for GPP treatment available, could help to reduce the burden on patients with GPP. Effective therapies that control and prevent GPP flares and manage chronic disease are needed.

Pustular psoriasis: A distinct aetiopathogenic and clinical entity

Pustular psoriasis is a distinct subset of psoriasis that presents with involvement of the skin in the form of sterile pustules along with systemic manifestations. Though it has been conventionally grouped under the umbrella of psoriasis, recent research has shed light on its pathogenetic mechanisms associated with the IL-36 pathway, which is distinct from conventional psoriasis. Pustular psoriasis in itself is a heterogeneous entity consisting of various subtypes, including generalised, localised, acute, and chronic forms. There is confusion regarding its current classification as entities like deficiency of IL-36 antagonist (DITRA) which are closely related to pustular psoriasis both in their pathogenetic mechanism and its clinical manifestations, are not included under pustular psoriasis. Entities like palmoplantar pustulosis, which presents with similar clinical features but is pathogenetically distinct from other forms of pustular psoriasis, are included under this condition. Management of pustular psoriasis depends upon its severity; while some of the localised variants can be managed with topical therapy alone, the generalised variants like Von Zumbusch disease and impetigo herpetiformis may need intensive care unit admission and tailor-made treatment protocols. The advent of newer biologics and better insight into the pathogenesis of pustular psoriasis has opened the way for newer therapies, including tumour necrosis factor-alpha inhibitors, interleukin-1 inhibitors, interleukin-17 inhibitors, and granulocyte monocyte apheresis. It continues to be an enigma whether pustular psoriasis is actually a variant of psoriasis or an entirely different disease entity, though we feel that it is an entirely different disease process.

The role of the interleukin-36 axis in generalized pustular psoriasis: a review of the mechanism of action of spesolimab

Generalized pustular psoriasis (GPP) is a rare, chronic, inflammatory skin disorder characterized by recurrent flares associated with skin erythema, desquamation, and widespread superficial sterile pustules, which may be severe ("lakes of pus"). Systemic symptoms are often present, including malaise, fever, and skin pain. In GPP, innate immune responses are driven by abnormal activation of the interleukin (IL)-36-chemokine-neutrophil axis and excessive neutrophil infiltration. This review highlights the IL-36 pathway in the context of the IL-1 superfamily and describes how unopposed IL-36 signaling can lead to the development of GPP. Targeted inhibition of the IL-36 receptor (IL-36R) is an attractive therapeutic strategy in the treatment of GPP, including flare prevention and sustained disease control. Spesolimab is a first-in-class, humanized, monoclonal antibody that binds specifically to the IL-36R and antagonizes IL-36 signaling. Spesolimab was approved by the US Food and Drug Administration in September 2022 to treat GPP flares in adults and was subsequently approved for GPP flare treatment in other countries across the world. Anti-IL-36R therapy, such as spesolimab, can mitigate flares and address flare prevention in GPP, presumably through rebalancing IL-36 signaling and modulating the pro-inflammatory response of the downstream effectors.

Efficacy and safety of subcutaneous spesolimab for the prevention of generalised pustular psoriasis flares (Effisayil 2): an international, multicentre, randomised, placebo-controlled trial

BACKGROUND

Spesolimab is an anti-interleukin-36 receptor monoclonal antibody approved to treat generalised pustular psoriasis (GPP) flares. We aimed to assess the efficacy and safety of spesolimab for GPP flare prevention.

METHODS

This multicentre, randomised, placebo-controlled, phase 2b trial was done at 60 hospitals and clinics in 20 countries. Eligible study participants were aged between 12 and 75 years with a documented history of GPP as per the European Rare and Severe Psoriasis Expert Network criteria, with a history of at least two past GPP flares, and a GPP Physician Global Assessment (GPPGA) score of 0 or 1 at screening and random assignment. Patients were randomly assigned (1:1:1:1) to receive subcutaneous placebo, subcutaneous low-dose spesolimab (300 mg loading dose followed by 150 mg every 12 weeks), subcutaneous medium-dose spesolimab (600 mg loading dose followed by 300 mg every 12 weeks), or subcutaneous high-dose spesolimab (600 mg loading dose followed by 300 mg every 4 weeks) over 48 weeks. The primary objective was to demonstrate a non-flat dose-response curve on the primary endpoint, time to first GPP flare.

FINDINGS

From June 8, 2020, to Nov 23, 2022, 157 patients were screened, of whom 123 were randomly assigned. 92 were assigned to receive spesolimab (30 high dose, 31 medium dose, and 31 low dose) and 31 to placebo. All patients were either Asian (79 [64%] of 123) or White (44 [36%]). Patient groups were similar in sex distribution (76 [62%] female and 47 [38%] male), age (mean 40·4 years, SD 15·8), and GPP Physician Global Assessment score. A non-flat dose-response relationship was established on the primary endpoint. By week 48, 35 patients had GPP flares; seven (23%) of 31 patients in the low-dose spesolimab group, nine (29%) of 31 patients in the medium-dose spesolimab group, three (10%) of 30 patients in the high-dose spesolimab group, and 16 (52%) of 31 patients in the placebo group. High-dose spesolimab was significantly superior versus placebo on the primary outcome of time to GPP flare (hazard ratio [HR]=0·16, 95% CI 0·05-0·54; p=0·0005) endpoint. HRs were 0·35 (95% CI 0·14-0·86, nominal p=0·0057) in the low-dose spesolimab group and 0·47 (0·21-1·06, p=0·027) in the medium-dose spesolimab group. We established a non-flat dose-response relationship for spesolimab compared with placebo, with statistically significant p values for each predefined model (linear p=0·0022, emax1 p=0·0024, emax2 p=0·0023, and exponential p=0·0034). Infection rates were similar across treatment arms; there were no deaths and no hypersensitivity reactions leading to discontinuation.

INTERPRETATION

High-dose spesolimab was superior to placebo in GPP flare prevention, significantly reducing the risk of a GPP flare and flare occurrence over 48 weeks. Given the chronic nature of GPP, a treatment for flare prevention is a significant shift in the clinical approach, and could ultimately lead to improvements in patient morbidity and quality of life.

FUNDING

Boehringer Ingelheim.

Challenges and Future Trends in the Treatment of Psoriasis

Psoriasis is a chronic inflammatory skin disorder, and current treatments include topical therapies, phototherapy, systemic immune modulators, and biologics, aiming to alleviate symptoms and improve quality of life. However, challenges persist, such as adverse effects, treatment resistance, high costs, and variability in response among individuals. The future of psoriasis treatment shows promising emerging trends. New biologic agents targeting novel pathways, such as interleukin 23 inhibitors like mirikizumab, offer enhanced efficacy. Small molecule inhibitors like RORγt inhibitors and ROCK2 inhibitors provide additional treatment options. Combination therapies, including biologics with methotrexate, may improve treatment response. Advancements in topical treatments utilizing microneedles and nanoparticle-based carriers can enhance drug delivery and improve therapeutic outcomes. Biomarkers and multi-omics technologies hold potential for personalized treatment approaches, thus aiding in diagnosis, predicting treatment response, and guiding therapeutic decisions. Collaboration among researchers, clinicians, and industry stakeholders is crucial to translating these scientific breakthroughs into clinical practice. By addressing current challenges and exploring these promising trends, we can optimize psoriasis management and improve the lives of those affected by this chronic condition.

Acrodermatitis continua of Hallopeau and generalised pustular psoriasis: Should they be the same or different entities?

Pustular psoriasis is characterised by eruptions of neutrophilic sterile pustules. The European Rare and Severe Psoriasis Expert Network consensus defines pustular psoriasis into three subtypes; generalised pustular psoriasis (GPP), palmoplantar pustulosis and acrodermatitis continua of Hallopeau (ACH). Mixed forms are categorised according to their predominant features. However, the Japanese Dermatological Association includes ACH under the diagnosis of GPP. This article aims to review the similarities and differences between ACH and GPP. Based on our review, interleukin (IL)-36RN mutations, the most frequent genetic findings in pustular psoriasis are found most commonly in GPP, followed by ACH. Genotypes of IL-36RN mutations among GPP patients and ACH patients are different between European and Asian ethnicities. IL-36 signalling pathway is the main mechanism. Metabolic diseases are common comorbidities and joint involvement can occur in 20.5%-36.4% of both conditions. Associated plaque psoriasis is more common in GPP than in ACH. Generally, ACH, even the generalised type, does not have systemic inflammation whereas GPP can occur with or without systemic inflammation. ACH can occur before, simultaneously, or after the development of GPP. However, response to treatment for GPP and ACH even in the same patients appear to be different. ACH seemed to be more recalcitrant to treatment than GPP but severe flare of GPP can lead to morbidity and mortality. Although GPP and ACH share genotypes and pathogenesis, we believe that ACH should be classified separately from GPP, and not under diagnosis of GPP. Future research is warranted to satisfactorily distinguish the two conditions.

A viewpoint on the genetic determinants of generalised pustular psoriasis

Generalised pustular psoriasis (GPP) is a rare and severe neutrophilic skin disorder, manifesting with acute episodes of pustulation and systemic upset. The discovery of recessive IL36RN mutations associated with GPP has transformed our understanding of disease drivers, paving the way for the development of targeted anti-IL36 therapeutics. In the light of these remarkable successes, this viewpoint reviews the significance of IL36RN mutations in GPP, their functional impact and their correlation with clinical phenotypes. It then covers the discovery of further genetic determinants (recessive MPO mutations) and risk factors (AP1S3 and CARD14 low-frequency variants) for the disease. It discusses the growing evidence for genetic complexity in GPP and concludes by outlining collaborative strategies that may be adopted to overcome the challenges ahead.

Diversity in the clinical presentation of generalized pustular psoriasis (GPP): A series of case vignettes from around the world

A key principle of clinical studies and case reports is that they should reflect the demographics and epidemiology of the patient population concerned. Here, we have compiled a diverse group of clinical cases of generalized pustular psoriasis (GPP) to showcase the differences in GPP presentation in patients worldwide. We attempt to capture the broad spectrum of clinical presentations of GPP and showcase the diversity of the patient population. The patients included in this series are diverse in age, genetic background, skin phototype and medical history. Moreover, they present with a variety of clinical courses of GPP and different degrees of systemic involvement, and experience flares triggered by different inciting factors. The key learnings from this case series may support physicians in identifying and managing patients with this rare and multifaceted disease that can affect patients both physically and psychologically.

Pathophysiology of generalized pustular psoriasis

Psoriasis is a chronic, immune-mediated skin disease that affects over 3% of adults in the United States. Psoriasis can present in several clinical forms. Of these, generalized pustular psoriasis is an acute, severe form, associated with increased morbidity and mortality. Unlike the more common plaque psoriasis, which is thought to feature dysregulation of the adaptive immune system, generalized pustular psoriasis reflects heightened autoinflammatory responses. Recent advances in genetic and immunological studies highlight a key role of the IL-36 immune axis in the pathogenesis of generalized pustular psoriasis. In this article, we review the psoriatic subtypes and discuss diagnostic criteria of generalized pustular psoriasis, discuss several newly identified genetic variants associated with pustular disease in the skin, and discuss how these mutations shed light on pustular disease mechanisms. Furthermore, we gather insights from recent transcriptomic studies that similarly implicate a pathogenic role of the IL-36 immune axis in generalized pustular psoriasis.

Clinical profile of patients with acute generalized pustular psoriasis with and without IL36RN mutations in multi-ethnic Johor Bahru, Malaysia

Generalized Pustular psoriasis (GPP), a rare and potentially life-threatening auto-inflammatory disease, is associated with IL36RN mutations. Here, we analyse the prevalence of IL36RN mutations in our multi-ethnic GPP cohort and assess differences in the clinical profile of patients with (IL36RN-positive) and without (IL36RN-negative) mutations. IL36RN mutations were present in 17.7% of 137 GPP patients (29.7% of Chinese cases, 17.3% of Malay cases, but 0% of Indian patients). 92% of these individuals carried the c.115 + 6 T > C mutation. Male: female ratio was 1:2.3. Females predominate in both groups with no significant difference between IL36RN-positive and IL36RN-negative individuals. The overall mean age (±SD) at disease onset for GPP was 37.6 ± 17.2 years, but disease onset was significantly earlier in IL36RN-positive vs IL36RN-negative cases (mean age:30.6 ± 18.92 vs. 39.2 ± 16.49 years, p = 0.027). IL36RN-positive patients were less likely to have associated plaque psoriasis (52.4% vs. 83.5%, p-value = 0.002). There was no difference in the common clinical and laboratory manifestations or triggers of GPP between IL36RN-positive and -negative patients, except for geographic tongue which was significantly more common in IL36RN-positive patients (41.7% vs. 11.9%, p-value = 0.002). Annual flare rate was significantly higher in IL36RN-positive compared to IL36RN-negative (mean ± SD of 1.92 ± 1.32 vs. 1.46 ± 0.90, p = 0.041) cases. However, no significant difference in the rate of hospitalization and length of hospital stay was observed between the two groups. These observations demonstrate that IL36RN disease alleles occur with varying frequencies among Asian populations and are associated with a severe, early-onset clinical phenotype.

A Transcriptome-Wide Analysis of Psoriasis: Identifying the Potential Causal Genes and Drug Candidates

Psoriasis is a chronic inflammatory skin disease characterized by cutaneous eruptions and pruritus. Because the genetic backgrounds of psoriasis are only partially revealed, an integrative and rigorous study is necessary. We conducted a transcriptome-wide association study (TWAS) with the new Genotype-Tissue Expression version 8 reference panels, including some tissue and multi-tissue panels that were not used previously. We performed tissue-specific heritability analyses on genome-wide association study data to prioritize the tissue panels for TWAS analysis. TWAS and colocalization (COLOC) analyses were performed with eight tissues from the single-tissue panels and the multi-tissue panels of context-specific genetics (CONTENT) to increase tissue specificity and statistical power. From TWAS, we identified the significant associations of 101 genes in the single-tissue panels and 64 genes in the multi-tissue panels, of which 26 genes were replicated in the COLOC. Functional annotation and network analyses identified that the genes were associated with psoriasis and/or immune responses. We also suggested drug candidates that interact with jointly significant genes through a conditional and joint analysis. Together, our findings may contribute to revealing the underlying genetic mechanisms and provide new insights into treatments for psoriasis.

Efficacy and safety of spesolimab for the management of generalized pustular psoriasis: a drug safety evaluation

INTRODUCTION

Generalized pustular psoriasis (GPP) is a rare form of psoriasis (less of 1% of cases). Currently, GPP is recognized as a clinical entity, distinguished from plaque psoriasis. However, there are not guidelines for GPP management and treatments are often derived from plaque psoriasis. Therefore, conventional systemic drugs are usually used as first-line treatment options, and biologics are still used off label. Recently, spesolimab, an anti-IL36 receptor humanized IgG1 monoclonal antibody, has been specifically approved for GPP disease, revolutionizing treatment scenario.

AREAS COVERED

The aim of this review is to investigate current literature on the use of spesolimab for GPP management to underline its potential role in GPP and offer a current clinical perspective. Literature research using the Google Scholar, Pubmed, Embase, Cochrane Skin, and clinicaltrials.gov databases was performed, selecting the most relevant manuscripts.

EXPERT OPINION

Spesolimab is efficacious and has a consistent and favorable safety profile in patients presenting with a GPP flare. However, despite excellent results in terms of safety and efficacy have been reported by both clinical trials and very limited real-life experiences, long-term data, especially in flare-up prevention, are scant. Thus, while the available data are encouraging, further research is warranted to understand the efficacy, safety, and long-term outcomes associated with spesolimab treatment in GPP.

Exploring the Clinical Features, Immunopathogenesis and Approach to Diagnosis for Generalized Pustular Psoriasis [Podcast]

Generalized pustular psoriasis is a rare presentation of psoriatic disease and is characterized by the acute onset of diffuse superficial pustules on the skin. These pustules can often coalesce, forming what's known as 'lakes of pus' that are most often seen on the trunk and on skin folds. GPP flares are often accompanied by systemic symptoms, including fever, malaise, and edema. The interleukin (IL)-36 pathway plays a central role in the development of GPP, although several other genes may be associated. The rarity of GPP makes its diagnosis challenging and it could be mistaken for an infectious condition or other types of pustular psoriasis, including unstable forms of plaque psoriasis that may present with pustules. Performing a thorough skin examination and obtaining a detailed history are vital to exclude these differential diagnoses. Incorrect or late diagnosis, inadequate or delayed treatment, and lack of specialist referrals may contribute to increased disease severity and can have a debilitating impact on patients' quality of life. In this podcast, two US-based dermatologists discuss the clinical characteristics of GPP, highlight the central role of IL-36 in immunopathogenesis, and share practical approaches to recognizing and diagnosing the disease.

Targeting IL-36 in Inflammatory Skin Diseases

Interleukin (IL)-36 cytokines are members of the IL-1 superfamily of cytokines. IL-36 cytokines are composed of three agonists (IL-36α, IL-36β, and IL-36γ) and two antagonists (IL-36 receptor antagonist [IL36Ra] and IL-38). These work in innate and acquired immunity and are known to contribute to host defense and to the pathogenesis of autoinflammatory diseases, autoimmune diseases, and infectious diseases. In the skin, IL-36α and IL-36γ are mainly expressed by keratinocytes in the epidermis, although they are also produced by dendritic cells, macrophages, endothelial cells, and dermal fibroblasts. IL-36 cytokines participate in the first-line defense of the skin against various exogenous assaults. IL-36 cytokines play significant roles in the host defense system and in the regulation of inflammatory pathways in the skin, collaborating with other cytokines/chemokines and immune-related molecules. Thus, numerous studies have shown IL-36 cytokines to play important roles in the pathogenesis of various skin diseases. In this context, the clinical efficacy and safety profiles of anti-IL-36 agents such as spesolimab and imsidolimab have been evaluated in patients with generalized pustular psoriasis, palmoplantar pustulosis, hidradenitis suppurativa, acne/acneiform eruptions, ichthyoses, and atopic dermatitis. This article comprehensively summarizes the roles played by IL-36 cytokines in the pathogenesis and pathophysiology of various skin diseases and summarizes the current state of research on therapeutic agents that target IL-36 cytokine pathways.

Prevalence, comorbidities and mortality of generalized pustular psoriasis: A literature review

Generalized pustular psoriasis (GPP) is a rare auto-inflammatory skin disease characterised by acute episodes of sterile pustule formation. Diagnosis and treatment of the disease have historically been complicated by a lack of awareness, and no consistent global definition or clinical coding standards. Now acknowledged as a distinct clinical entity with a recognised genetic component, GPP can take a serious and life-threatening course due to systemic inflammatory complications and its association with various comorbidities. As with other rare diseases, there are significant challenges to understanding the epidemiology of GPP, notably a small patient population, non-standardised study methodologies and ethnic differences in its presentation. A clearer understanding of GPP is therefore required for clinicians to better manage patients with this rare condition. In this review article, we present an overview of the available data on GPP prevalence estimates in key demographics and report the frequency of genetic mutations associated with the disease. We detail the incidence of known comorbidities and summarise the data on mortality and assigned causes of death. Lastly, we discuss the various factors that impact the collection, interpretation and comparison of these data.

Case report: Infantile generalized pustular psoriasis with IL36RN and CARD14 gene mutations

Infantile pustular psoriasis (IPP) is an extremely rare skin disease associated with genetic factors. Gene mutations of IL36RN (interleukin-36 receptor antagonist), CARD14 (caspase recruitment family member 14), and AP1S1 (the σ1C subunit of the adaptor protein complex 1) had been identified to be involved in the pathogenesis of IPP. IPP usually develops with no preceding psoriasis vulgaris (PV) or familial history. Here, we report a case of a 6-month-old infant and make the diagnosis of IPP by a series of examinations; subsequently, by detecting coexistent mutations of IL36RN and CARD14, the diagnosis is intensified from a genetic point of view. We treated the child with traditional oral and topical drugs regardless of the commonly used acitretin considering its potential side effects, such as skeletal toxicity, and the lesions got conspicuous improvement with much reduction of inflammation. Owing to the genetic mutation of IL-36, there had been reported cases focusing on anti-IL36 biological agents in the treatment of IPP, and it could be a new weapon to treat and improve such IL-36RN-deficient skin diseases.

Pustular psoriasis with a focus on generalized pustular psoriasis: classification and diagnostic criteria. An Italian expert consensus

Generalized pustular psoriasis (GPP) is a severe and life-threatening systemic disease associated with significant morbidity and mortality. Recent progress has been made in understanding the pathogenetic pathways involved in GPP and an intricate interaction between innate and adaptive immune mechanisms has been suggested. Despite formal consensus guidelines on pustular psoriasis currently available in the literature, the definitions and classifications of GPP used across studies were inconsistent. Consequently, there are no unified criteria that can be universally adopted for precise diagnosis, classification and effective treatment of GPP patients with new targeted drugs. The aim of this review was to collect all the main evidence on available diagnostic criteria for GPP and to establish recommendations in order to promote a better stratification and therapeutic management of this severe and heterogeneous disease.

Correlation of IL36RN and CARD14 mutations with clinical manifestations and laboratory findings in patients with generalised pustular psoriasis

Background

Generalized pustular psoriasis (GPP) is a chronic disease associated with genetic factors related to mutations of the interleukin 36 receptor antagonist gene (IL36RN) and the caspase recruitment domain 14 gene (CARD14). However, the relevance of these mutations to the clinical features and severity of GPP remains unclear.

Aims

Our objective was to correlate the presence of IL36RN and CARD14 mutations with the clinical and laboratory findings in patients with GPP.

Methods

This cross-sectional descriptive study was conducted in 64 subjects with GPP. Clinical manifestations were recorded and the severity was graded as mild, moderate, or severe. Routine laboratory tests were performed and blood samples were collected for Sanger sequencing. The clinical data of patients were compared among the different mutation groups.

Results

The two main variants of IL36RN were c.115+6T > C (p.Arg10ArgfsX1) and c.227C > T (p.Pro76Leu). The major CARD14 mutations were c.2458C > T (p.Arg820Trp), c.1641C > T (p.Arg547Ser), and c.1753G > A transitions.

Provocative factors were uncommon in the group with both IL36RN and CARD14 mutations. Drugs (unspecified), especially herbals, were the most common triggers. A history of psoriasis was frequent in patients with only CARD14 mutations, but fever was uncommon. The c.1641C > T mutation was associated with leukocytosis > 15000/mm3 and the c.1753G > A mutation was associated with hypoalbuminemia <3.8g/dL.

Both the c.115+6T > C and c.227C > T variants of IL36RN were associated with fever ≥38.5°C while the c.115+6T > C variant was also associated with geographic tongue.

No gene mutations were associated with the total severity and severity grades.

Limitations

Four patients without the two major IL36RN mutations were excluded from the study.

Conclusion

The presence of IL36RN and CARD14 mutations were associated with a history of psoriasis, various provocative factors, fever, leukocytosis, hypoalbuminemia, and geographic tongue. Further studies to explore the role of these mutations in therapeutic efficacy and disease outcomes are necessary.

Generalized pustular psoriasis is a disease distinct from psoriasis vulgaris: evidence and expert opinion

INTRODUCTION

Generalized pustular psoriasis (GPP) is a rare, severe, clinically heterogeneous disease characterized by flares of widespread, non-infectious, macroscopically visible pustules that occur with or without systemic inflammation, and are associated with significant morbidity and mortality. Historically, GPP has been classified as a variant of psoriasis vulgaris (PV, or plaque psoriasis); however, accumulating evidence indicates that these are distinct conditions, requiring different treatment approaches.

AREAS COVERED

In this perspectives article we review evidence that supports the classification of GPP as distinct from PV.

EXPERT OPINION

The histopathologic and clinical appearance of GPP is distinct from that of PV and fundamental differences exist between the two conditions in terms of genetic causes and expression-related mechanisms of disease development. GPP results from dysregulation of the innate immune system, with disruption of the interleukin (IL)-36 inflammatory pathway, induction of inflammatory keratinocyte responses, and recruitment of neutrophils. PV is driven by the adaptive immune system, with a key role played by IL-17. Considering GPP as a separate disease will enable greater focus on its specific pathogenesis and the needs of patients. Many treatments for PV have insufficient efficacy in GPP and a therapeutic approach developed specifically for GPP might lead to better patient outcomes.

Generalized Pustular Psoriasis in Pregnancy: Current and Future Treatments

Generalized pustular psoriasis (GPP) is a rare, severe neutrophilic skin disease characterized by sudden widespread eruption of sterile pustules with or without systemic symptoms. GPP may be life threatening in cases with severe complications such as cardiovascular failure, acute respiratory distress syndrome, and serious infections. Impetigo herpetiformis (IH) is a GPP that is induced and exacerbated by pregnancy and occurs most frequently during the last trimester. IH may result in poor or fatal neonatal outcomes, including placental insufficiency, fetal abnormalities, stillbirth, and early neonatal death. Most patients have prompt remission in the postpartum period; however, earlier appearance and more severe symptoms are observed during subsequent pregnancies. Appropriate treatment and close monitoring of the mother and fetus are vital for the management of patients with IH. Particular attention is required for the management of patients with IH to avoid an influence on the fetus. However, data regarding treatments for GPP in pregnant women are sparse. Over the last decade, many patients with IH have been treated with cyclosporine, corticosteroids, tumor necrosis factor-α inhibitors, interleukin (IL)-17 and IL-12/23 inhibitors, and granulocyte and monocyte adsorption apheresis (GMA). GMA may be an important option for patients with IH as it is presently one of the safest available therapeutic options, but there have been no reports to fully confirm its safety in pregnant patients with GPP. Alternatively, based on recent advances in the understanding of the role of the IL-36 axis in the pathogenesis of GPP, biologic agents that target the IL-36 pathway may demonstrate promising efficacy in IH.

Novel Therapeutic Target(s) for Psoriatic Disease

Psoriasis and psoriatic arthritis, together known as psoriatic disease, is highly prevalent chronic relapsing inflammatory disease affecting skin, joints or both and is associated with several comorbidities such as cardiovascular, metabolic, psychiatric, renal disease etc. The etiopathogenesis of psoriasis is complex and mainly driven by aberrant immune response owing to the genetic susceptibility and various environmental factors such as trauma, infections and drugs. Recent advances in understanding molecular and cellular pathways have identified tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), IL-23, IL-22 as major contributors in psoriasis pathogenesis. Advances in the knowledge of pathophysiology, the interaction of autoinflammation and clinical phenotypes have led to the development of highly effective targeted therapeutic agents which include TNF-α, IL-17, IL-23, IL-1 α/β or IL-36 inhibitors or receptor blockers, small molecule drugs like phosphodiesterase-4 inhibitors (apremilast), Janus kinase (JAK) inhibitors, retinoic acid receptor-related orphan receptor γt (RORγt) inhibitors. These novel drugs have promised the potential of improved disease control. In recent years, the transition from biologics to biosimilars especially with TNF-α inhibitors had significant impact on decreasing health care cost and increasing therapeutic options to the patients. However, selection of right treatment for an individual patient still remains challenging. Moreover, interplay between different epigenetic mechanisms such as the DNA methylation, chromatin modifications and noncoding RNA regulation has recently been started to be deciphered. Enzymes inhibitors involved in epigenetic pathways such as DNA methyltransferases and histone deacetylases demonstrated to restore normal epigenetic patterns in clinical settings and have provided the potential as novel therapeutic targets for psoriasis. In this review, we will discuss novel biologic agents and newer therapeutic approaches in treatment of psoriatic disease.

Clinical Course and Characteristics of Generalized Pustular Psoriasis

Generalized pustular psoriasis (GPP) is a rare, potentially life-threatening disease characterized by episodes of widespread sterile macroscopic pustules, with or without systemic inflammation and/or plaque psoriasis. Multiple GPP subtypes have been described, from acute GPP of von Zumbusch to milder, annular pustular psoriasis. Generalized pustular psoriasis mainly affects adults, with a female preponderance, but juvenile GPP also occurs. Flares are a hallmark of GPP and may occur de novo or be provoked by triggers, including withdrawal of systemic corticosteroids, infections, stress, pregnancy, and menstruation. Severity of flares varies widely between patients, and between flares in an individual patient. Significant flares are often accompanied by systemic symptoms, notably fever, general malaise, and extracutaneous manifestations such as arthritis, uveitis, and neutrophilic cholangitis. Common laboratory abnormalities include neutrophilia, elevated C-reactive protein levels, hypocalcemia, and abnormal liver function tests. The clinical course of GPP is highly variable; it can be a relapsing disease with recurrent flares and no pustulation between flares or a persistent disease with perpetual mild pustulation punctuated with flares of greater severity. Patients may have multiple flares per year or a flare every few years. Most flares last 2–5 weeks and approximately 50% require hospitalization. Life-threatening complications include sepsis and renal, hepatic, respiratory, and heart failure. Reported mortality rates are 2–16%.

Pathophysiology of Generalized Pustular Psoriasis

Generalized pustular psoriasis (GPP) is a rare, severe form of pustular psoriasis characterized by widespread, recurrent episodes of neutrophil-rich pustule formation in the epidermis, which can be accompanied by fever and systemic inflammation. Recent clinical, histologic, and genetic evidence indicates that GPP is a distinct entity from plaque psoriasis, with different cytokine pathways predominant in the manifestation of each disease. The interleukin-36 (IL-36) signaling cascade plays a key role in regulating the innate immune system, and its dysregulation appears central to the pathogenesis of GPP. The altered expression of various IL-36 pathway constituents has been shown to cause a positive feedback loop of uncontrolled signaling and excess production of inflammatory cytokines, which in turn leads to chemokine induction and neutrophil recruitment in the epidermis. Given the potentially life-threatening nature of GPP episodes, drug interventions that rapidly achieve disease resolution are required. Early phase data indicate that treatments targeting various components of the IL-36 inflammatory cascade represent promising areas of research. However, there are currently no therapeutic agents specifically approved for GPP in the USA or Europe. Understanding the inflammatory pathways, associated risk factors, and role of neutrophils in the manifestation and perpetuation of GPP flares remains a key goal in developing effective therapeutics. In this article, we summarize the current understanding of GPP, describe novel therapeutic opportunities, and detail how the unique pathophysiology of the disease may inform future treatment strategies.

High-Throughput RNA Sequencing Reveals the Effect of NB-UVB Phototherapy on Major Inflammatory Molecules of Lesional Psoriasis

OBJECTIVE

To identify the narrowband ultraviolet B (NB-UVB)-induced molecular mechanisms that may account for their anti-inflammatory efficacy, gene expression and transcriptome profiling, which were performed using advanced molecular techniques.

METHODS

This research was conducted on patients with moderate-to-severe plaque-type psoriasis who received NB-UVB treatment. RNA sequencing (RNA-Seq) was conducted to assay the transcriptomes and identify the differentially expressed transcripts that had been enriched during the major pathway analysis.

RESULTS

Clinical improvement of psoriasis by NB-UVB therapy is linked to the suppression of the "immunological signaling pathways" and "cell cycle regulatory, growth and proliferation pathways" which are critical to the pathogenesis of the disease. In addition, these results were further substantiated by demonstrating that NB-UVB therapy has a significant effect on keratinocyte differentiation and affects the regulation of genes and inflammatory mediators that are related to cell proliferation and apoptosis. Moreover, NB-UVB phototherapy is also involved with the downregulation of toll-like receptors signaling in lesional psoriasis.

CONCLUSION

NB-UVB is an effective treatment for psoriasis. Our study supports the conclusion that the clinical effectiveness of NB-UVB therapy is based on the suppression of a broad range of inflammatory signaling pathways, gene expression of inflammatory cytokines and increased expressions of anti-inflammatory signaling pathways in psoriatic skin. This is the first study that applied advanced molecular techniques to investigate phototherapy as a new key to unlock genetic knowledge and create novel information. Ultimately, the goal is to increase medical knowledge and improve the patient care of psoriasis.

Pustular psoriasis as an autoinflammatory keratinization disease (AiKD): Genetic predisposing factors and promising therapeutic targets

Pustular psoriasis is a chronic inflammatory skin disease characterized by erythematous plaques with sterile pustules. It includes the distinct clinical entities generalized pustular psoriasis (GPP), acrodermatitis continua of Hallopeau (ACH) and palmoplantar pustular psoriasis (PPPP). Recently clarified pathomechanisms of pustular psoriasis indicate that hyperactivation of the skin innate immunity, including of the IL-1/IL-36 axis, plays an important role in the pathogenesis of pustular psoriasis. Autoinflammatory keratinization disease (AiKD) is the umbrella clinical entity for inflammatory keratinization disorders with genetic autoinflammatory pathomechanisms, and pustular psoriasis is a representative AiKD. To date, mutations/variants in five genes-IL36RN, CARD14, AP1S3, MPO and SERPINA3-have been reported to be genetic causative or predisposing factors for pustular psoriasis. The pathogenic mechanisms induced by the mutations/variants in these genes are all closely related to the excessive activation of skin innate immunity and autoinflammation. A number of biologics (e.g., tumor necrosis factor inhibitors, IL-17/IL-17 receptor inhibitors and IL-23 inhibitors) and granulocyte and monocyte adsorption apheresis are used to treat pustular psoriasis. Recently, based on novel information on the pathomechanisms of pustular psoriasis, which are mainly associated with autoinflammation, inhibitors of several pathogenic pathways, including of the IL-1, IL-36, IL-8 and granulocyte colony-stimulating factor signaling pathways, have been studied as emerging treatments.

Generalized pustular psoriasis (von Zumbusch)

Generalized pustular psoriasis (von Zumbusch) is a rare and acute eruption characterized by multiple sterile pustules over an erythematous and edematous background, eventually associated with psoriasis vulgaris. Classically, it manifests as a potentially severe systemic picture and demands prompt diagnosis and intervention. The duration of each flare-up and intervals between the pustular episodes is extremely variable. Recently, genetic abnormalities have been identified mainly in the familial and early variants of this disease. The therapeutic arsenal is limited; however, new drugs being evaluated aim to control both pustular flare-ups and disease recurrences.

Pustular Psoriasis: From Pathophysiology to Treatment

Pustular psoriasis (PP) is a clinicopathological entity encompassing different variants, i.e., acute generalized PP (GPP), PP of pregnancy (impetigo herpetiformis), annular (and circinate) PP, infantile/juvenile PP, palmoplantar PP/palmoplantar pustulosis, and acrodermatitis continua of Hallopeau (ACH), which have in common an eruption of superficial sterile pustules on an erythematous base. Unlike psoriasis vulgaris, in which a key role is played by the adaptive immune system and interleukin (IL)-17/IL-23 axis, PP seems to be characterized by an intense inflammatory response resulting from innate immunity hyperactivation, with prominent involvement of the IL-36 axis. Some nosological aspects of PP are still controversial and debated. Moreover, owing to the rarity and heterogeneity of PP forms, data on prognosis and therapeutic management are limited. Recent progresses in the identification of genetic mutations and immunological mechanisms have promoted a better understanding of PP pathogenesis and might have important consequences on diagnostic refinement and treatment. In this narrative review, current findings in the pathogenesis, classification, clinical features, and therapeutic management of PP are briefly discussed.

Pustular Psoriasis: A Narrative Review of Recent Developments in Pathophysiology and Therapeutic Options

Pustular psoriasis is an unusual form of psoriasis that frequently presents clinical challenges for dermatologists. The condition presents with pustules on an erythematous background and has two distinct subtypes: localized disease on the palms and soles, called palmoplantar pustulosis (PPP), and generalized pustular psoriasis (GPP). The involvement of the fingers, toes, and nails is defined as a separate localized variant, acrodermatitis continua of Hallopeau, and is now thought to be a subset of PPP. The rarity of pustular psoriasis frequently makes the correct diagnosis problematic. In addition, treatment is limited by a relative lack of evidence-based therapeutic options. Current management is often based on existing therapies for standard plaque psoriasis. However, there remains a need for treatments with high, sustained efficacy and a rapid onset of action in pustular psoriasis. Recent advances in understanding of the pathogenesis of pustular psoriasis have provided insights into potential therapies. Treatment of pustular psoriasis is generally determined by the extent and severity of disease, and recent years have seen an increasing use of newer agents, including biologic therapies. Current classes of biologic therapies with US Food and Drug Administration and European Medicines Agency approval for treatment of moderate-to-severe plaque psoriasis in the USA (and elsewhere) include tumor necrosis factor alpha inhibitors (adalimumab, certolizumab pegol, etanercept, infliximab), interleukin (IL)-17 inhibitors (brodalumab, ixekizumab, secukinumab), an IL-12/23 inhibitor (ustekinumab), and IL-23 inhibitors (guselkumab, risankizumab, tildrakizumab). Recently, specific inhibitors of the IL-36 pathway have been evaluated in GPP and PPP, including spesolimab, an IL-36 receptor inhibitor which has shown promising results in GPP. The emerging drugs for pustular psoriasis offer the possibility of rapid and effective treatment with lower toxicities than existing therapies. Further research into agents acting on the IL-36 pathway and other targeted therapies has the potential to transform the future treatment of patients with pustular psoriasis. This article reviews the clinical features of PPP and GPP, and current understanding of the genetics and immunopathology of these conditions; it also provides an update on emerging treatments.

Pustular psoriasis is a skin condition where people develop small pus-filled blisters on their skin. Pustular psoriasis may affect certain areas of the body, such as the palms and/or the soles. This is called palmoplantar pustulosis (PPP for short). Another type of pustular psoriasis can affect most of the body called generalized pustular psoriasis (GPP for short). Not many people have PPP or GPP. Around 5–12 in every 10,000 people worldwide develop PPP. GPP is even rarer, affecting only 2–7 out of every 1 million people. In addition to being relatively uncommon, these conditions are challenging to treat. This article aims to help doctors who treat skin conditions (dermatologists) to identify and treat people with pustular psoriasis. Currently there is no standard treatment for GPP and PPP in the USA or Europe, but several medicines are approved for treatment of GPP in Japan. Doctors often use treatments that have been shown to work in plaque psoriasis, which is the most common type of psoriasis, to treat people with GPP and PPP. Traditional treatments for PPP and GPP are often not effective. Researchers are working on developing new effective treatments for pustular psoriasis that may work more rapidly and have fewer side effects. These are expected to be available in the next few years.

Pustular Psoriasis and Acute Generalized Exanthematous Pustulosis

The similarity between pustular psoriasis (PP) and acute generalized exanthematous pustulosis (AGEP) poses problems in the diagnosis and treatment of these two conditions. Significant clinical and histopathologic overlap exists between PP and AGEP. PP is an inflammatory disorder that has numerous clinical subtypes, but all with sterile pustules composed of neutrophils. AGEP is a severe cutaneous adverse reaction that is also characterized by non-follicular sterile pustules. Clinical features that suggest a diagnosis of PP over AGEP include a history of psoriasis and the presence of scaling plaques. Histologically, eosinophilic spongiosis, vacuolar interface dermatitis, and dermal eosinophilia favor a diagnosis of AGEP over PP. Importantly, PP and AGEP vary in clinical course and treatment. PP treatment involves topical steroids, oral retinoids, and systemic immunosuppressants. Newer therapies targeting IL-36, IL-23, IL-1, and PDE-4 have been investigated. The removal of the offending agent is a crucial part of the treatment of AGEP.

Generalized Pustular Psoriasis: Divergence of Innate and Adaptive Immunity

Generalized pustular psoriasis (GPP) is a severe, relapsing, immune-mediated disease characterized by the presence of multiple sterile pustules all over the body. The exact pathomechanisms behind GPP remain elusive, although increased interest in the genetic basis and immunological disturbances have provided some revealing insights into the underlying signaling pathways and their mutual interaction. The genetic background of GPP has been thoroughly investigated over the past few years. The conducted studies have identified genetic variants that predispose to pustular forms of psoriasis. The loss-of-function mutation of the interleukin 36 receptor antagonist gene, along with rare gain-of-function mutations in the gene that encodes the keratinocyte signaling molecule (CARD14), are examples of the uncovered abnormalities. Interleukin 36 (IL-36), along with neutrophils, is now considered a central cytokine in GPP pathogenesis, with IL-36 signaling providing a link between innate and adaptive immune responses. More recently, a new concept of inflammation, caused by a predominantly genetically determined abnormal activation of innate immune response and leading to inflammatory keratinization, has arisen. GPP is currently considered a representative of this novel group of skin conditions, called autoinflammatory keratinization diseases. As no therapeutic agents have been approved for GPP to date in the United States and Europe, the novel anti-IL-36R antibodies are particularly promising and may revolutionize management of the disease.

Generalized pustular psoriasis: current management status and unmet medical needs in Japan

INTRODUCTION

Generalized pustular psoriasis (GPP) is a rare, inflammatory skin disease characterized by recurrent flares of pustulation accompanied by systemic symptoms that can be life-threatening. The clinical and humanistic burden of GPP in Japan is high, and it is a designated intractable disease. We reviewed clinical evidence and guidelines for GPP treatment in Japan to identify unmet needs and assess data supporting the development and use of new targeted therapies.

AREAS COVERED

Using specific search terms in PubMed and Embase, with additional back-referencing, we retrieved literature related to GPP in Japan focusing on clinical and pathogenic characteristics, diagnosis, and treatment.

EXPERT OPINION

Although there are approved systemic therapies for GPP in Japan, all present uncertainties in terms of safety and efficacy. Clinical evidence supporting their use comes mostly from studies in patients with mild or moderate disease, and their effectiveness in treating acute phase GPP is unknown. The interleukin-36 pathway appears to be central to GPP pathogenesis. New therapies targeting this pathway show promise in patients presenting with acute phase GPP. The rarity and intermittent course of GPP make it challenging to recruit sufficient patients for trials and robustly investigate the efficacy and safety of these agents to treat GPP.

An update on genetic basis of generalized pustular psoriasis (Review)

Generalized pustular psoriasis (GPP) is a rare and severe auto-inflammatory skin disease that is characterized by recurrent, acute onset, and generalized pustular eruptions on erythematous, inflamed skin. GPP is traditionally classified as a variant of psoriasis vulgaris, even though recent clinical, histological and genetic evidence suggests that it is a heterogeneous disease and requires a separate diagnosis. In recent years, variants of IL36RN, CARD14, AP1S3 and MPO genes have been identified as causative or contributing to genetic defects in a proportion of patients affected by GPP. These disease-related genes are involved in common inflammatory pathways, in particular in the IL-1/IL-36-chemokines-neutrophil pathogenic axis. At present, no standard therapeutic guidelines have been established for GPP management, and there is a profound need for novel efficacious treatments of GPP. Among them, biological agents antagonizing the IL-36 pathway are promising therapeutics. The aim of the present review is to provide the most recent updates on the genetics, genotype-phenotype correlation and pathological basis of GPP, as well as on biologic treatments available for GPP and relative clinical courses.

Exploring the Role of IL-36 Cytokines as a New Target in Psoriatic Disease

Unmet needs in the treatment of psoriasis call for novel therapeutic strategies. Pustular psoriasis and psoriatic arthritis often represent a therapeutic challenge. Focus on IL-36 cytokines offers an interesting approach, as the IL-36 axis has been appointed a critical driver of the autoinflammatory responses involved in pustular psoriasis. Two IL-36R blocking antibodies, imsidolimab and spesolimab, are currently undergoing phase II and III clinical trials, with promising results.

IL-1 Family Antagonists in Mouse and Human Skin Inflammation

Interleukin (IL)-1 family cytokines initiate inflammatory responses, and shape innate and adaptive immunity. They play important roles in host defense, but excessive immune activation can also lead to the development of chronic inflammatory diseases. Dysregulated IL-1 family signaling is observed in a variety of skin disorders. In particular, IL-1 family cytokines have been linked to the pathogenesis of psoriasis and atopic dermatitis. The biological activity of pro-inflammatory IL-1 family agonists is controlled by the natural receptor antagonists IL-1Ra and IL-36Ra, as well as by the regulatory cytokines IL-37 and IL-38. These four anti-inflammatory IL-1 family members are constitutively and highly expressed at steady state in the epidermis, where keratinocytes are a major producing cell type. In this review, we provide an overview of the current knowledge concerning their regulatory roles in skin biology and inflammation and their therapeutic potential in human inflammatory skin diseases. We further highlight some common misunderstandings and less well-known observations, which persist in the field despite recent extensive interest for these cytokines.

Excellent response to secukinumab in an infant with severe generalized pustular psoriasis

Generalized pustular psoriasis (GPP) represents the rarest form of psoriasis, which may be potentially fatal. In the last decade, (likely) pathogenic variants in the IL36RN, CARD14 and AP1S3 genes have been associated with monogenic GPP forms. Despite these advances, the genetic basis of most patients with GPP remains unidentified. Treatment of GPP patients is often difficult, with no consensus about the best available options to date. We report herein an infant with severe GPP in whom the disease started at the age of 2 months. Genetic investigations identified a heterozygous pathogenic variant in the IL36RN gene associated with a heterozygous variant of uncertain significance in the CARD14 gene. After previous treatment failures with acitretin, cyclosporin and anakinra, treatment with the interleukin-17 antagonist secukinumab resulted in a dramatic and prompt positive response that persisted at 12-month follow up. According to our experience, we believe secukinumab can be an effective and safe treatment for pediatric patients with GPP even before 1 year of age.

Association between mutation of interleukin 36 receptor antagonist and generalized pustular psoriasis: A PRISMA-compliant systematic review and meta-analysis

BACKGROUND

Generalized pustular psoriasis (GPP) is a systemic inflammatory disease with poor outcomes, and several studies have suggested that the mutation of the interleukin 36 receptor antagonist gene (IL36RN) is related to GPP, where the polymorphism c.115+6T>C is reported to be the most common mutation of IL36RN. This study was performed to clarify and comprehensively evaluate the relationship between IL36RN gene polymorphism and the susceptibility of GPP subtypes.

METHODS

To conduct a thorough literature review, studies were obtained using databases such as Pubmed, EMBASE, Cochrane, China National Knowledge Infrastructure, and the Wanfang database. Only studies published up to December 2019 were included. The quality of the research studies was estimated using the Newcastle-Ottawa scale. The total odds ratios (ORs) and corresponding 95% confidence intervals (95% CIs) were pooled and analysed using STATA 14. The publication bias was evaluated through the Egger test, performed using the aforementioned software. Five common gene models were built and analysed to assess the association between the polymorphism c.115+6T>C and subtypes of GPP.

RESULTS

A total of 10 studies were selected, including 683 cases of GPP patients. Meta-analyses showed that there was a significant statistical correlation of IL36RN mutation between GPP with or without psoriasis vulgaris (OR = 3.82, 95%CI 2.63-5.56) and between adult GPP and paediatric GPP (OR = 0.42, 95%CI 0.23-0.77). No obvious discrepancy between European patients (OR = 4.03, 95%CI 2.23-7.26) and Asian patients was found. The gene models showed clear associations between the polymorphism c.115+6T>C and GPP through the dominant model (CC+ TC vs TT, OR 2.74, 95%CI 2.06-3.64), recessive model (CC vs CT + TT, OR 4.33, 95%CI 2.84-6.60), homozygote model (CC vs TT, OR 4.37, 95%CI 2.88-6.62), heterozygote model (CT vs TT, OR 2.26, 95%CI 1.32-3.85) and allelic model (C vs T, OR 3.35, 95%CI 2.63-4.27).

CONCLUSION

The IL36RN mutation is strongly related to GPP without psoriasis vulgaris and the early onset of GPP. Furthermore, the single-nucleotide polymorphism c.115+6T>C of the IL36RN gene plays a significant role in GPP vulnerability, especially in homozygous mutation. GPP could be a different inflammatory disease, independent of psoriasis.

"Autoinflammatory psoriasis"-genetics and biology of pustular psoriasis

Psoriasis is a chronic inflammatory skin condition that has a fairly wide range of clinical presentations. Plaque psoriasis, which is the most common manifestation of psoriasis, is located on one end of the spectrum, dominated by adaptive immune responses, whereas the rarer pustular psoriasis lies on the opposite end, dominated by innate and autoinflammatory immune responses. In recent years, genetic studies have identified six genetic variants that predispose to pustular psoriasis, and these have highlighted the role of IL-36 cytokines as central to pustular psoriasis pathogenesis. In this review, we discuss the presentation and clinical subtypes of pustular psoriasis, contribution of genetic predisposing variants, critical role of the IL-36 family of cytokines in disease pathophysiology, and treatment perspectives for pustular psoriasis. We further outline the application of appropriate mouse models for the study of pustular psoriasis and address the outstanding questions and issues related to our understanding of the mechanisms involved in pustular psoriasis.

Pathogenesis of psoriasis in the "omic" era. Part II. Genetic, genomic and epigenetic changes in psoriasis

Psoriasis is a multifactorial disease in which genetic, environmental and epigenetic factors regulating gene expression play a key role. In the “genomic era”, genome-wide association studies together with target genotyping platforms performed in different ethnic populations have found more than 50 genetic susceptible markers associated with the risk of psoriasis which have been identified so far. Up till now, the strongest association with the risk of the disease has been proved for HLA-C*06 gene. The majority of other psoriasis risk SNPs are situated near the genes encoding molecules involved in adaptive and innate immunity, and skin barrier function. Many contemporary studies indicate that the epigenetic changes: histone modification, promoter methylations, long non-coding and micro-RNA hyperexpression are considered as factors contributing to psoriasis pathogenesis as they regulate abnormal keratinocyte differentiation and proliferation, aberrant keratinocytes – inflammatory cells communication, neoangiogenesis and chronic inflammation. The circulating miRNAs detected in the blood may become specific markers in the diagnosis, prognosis and response to the treatment of the disease. The inhibition of expression in selected miRNAs may be a new promising therapy option for patients with psoriasis.