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.

Current Treatments for Generalized Pustular Psoriasis: A Narrative Summary of a Systematic Literature Search

Generalized pustular psoriasis (GPP) is a rare, chronic and potentially life-threatening autoinflammatory skin disease characterized by widespread eruption of sterile pustules, with or without systemic inflammation. GPP can significantly reduce patients' quality of life (QoL). Several therapeutic approaches have been described in the literature, but there is no consensus on optimal treatment. In this review, we summarize published literature on efficacy, safety and QoL outcomes associated with current treatment of GPP with both approved and non-approved products. Embase and MEDLINE databases were searched (1980-September 2023). A search protocol was designed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered on the PROSPERO database (CRD42021215437). Details on publication, population, intervention, efficacy, safety and QoL were captured and checked by independent reviewers. In total, 118 publications were included, with only 19% of publications reporting on the results of clinical trials. Treatment modalities reported for GPP included non-biologic systemic therapies such as retinoids, cyclosporine and methotrexate, topical agents, biologics and small molecules, among others. Results were highly heterogeneous and methodological quality was very low, with only the interleukin-36R inhibitor spesolimab reporting results from placebo-controlled randomized trials; based on this, spesolimab is now approved for GPP treatment in regions including the USA, Japan, China, the EU and several other countries. Some other biologics are approved exclusively in Japan and Taiwan for the treatment of GPP based on open-label studies with small patient numbers in lieu of double-blind studies. Non-standardization of clinical outcomes across studies remains a major hurdle in reaching a consensus on optimal treatment. However, recently trials have been conducted using well-defined, disease-specific endpoints to evaluate GPP-targeted treatments, which will hopefully advance patient care. In conclusion, this review highlights the need for prospective randomized studies with GPP-specific endpoints to determine the optimal treatment strategy.

A Non-Interventional, Multicenter Study to Characterize the Socio-Demographics, Clinical Characteristics, and Management of Generalized Pustular Psoriasis Patients in Spain: IMPULSE Study

INTRODUCTION

Generalized pustular psoriasis (GPP) is a chronic, rare, and potentially life-threatening skin condition characterized by flares comprising widespread sterile pustules and systemic inflammation. Both the rarity and heterogeneity of the disease have made GPP classification and standardization of clinical criteria challenging. Before the approval of spesolimab (IL-36R antibody) in 2022, there were no approved treatments in the USA or Europe for GPP flares. Treatment for GPP has amounted to off-label use of medicines approved to treat plaque psoriasis. Our aim was to describe the sociodemographics, clinical characteristics, and treatment patterns of patients with GPP in Spain.

METHODS

Non-interventional, descriptive, multi-center, retrospective chart review of patients diagnosed with GPP in Spain.

RESULTS

56 patients (50% women) were included, with a mean (standard deviation, SD) age at diagnosis of 53.7 (20.5) and a mean (SD) time of follow-up of 3.7 (3.1) years. In 80% of patients, GPP diagnosis was associated with a flare and 67.3% had known risk factors for GPP (such as previous diagnosis or family history of plaque psoriasis, comorbidities, smoking or stress). Hypertension and plaque psoriasis were the most frequent comorbidities (44.6% each). The number of GPP flares per patient-year was 0.55 with (range 0-4) a mean (SD) body surface area involvement of 21.3% (19.1). The most frequent manifestations of GPP flares were pustules (88.5%), erythema (76.9%), and scaling (76.9%). Additionally, 65.4% of patients had plaque psoriasis, 53.8% had unspecified skin lesions, and 30.8% experienced pain. The treatments used for GPP flares were off-label conventional systemic drugs (75%), mostly corticosteroids, cyclosporine, and acitretin. In the periods between flares, off-label biologics were used in 56.5% of patients. During the study period, 9 patients (16.1%) had at least one complication and 5 of them required hospitalization.

CONCLUSION

This is the first multicenter study in Spanish GPP patients. Most patients were in their fifties, with personal or family history of plaque psoriasis, stress, smoking and a wide range of comorbidities and complications. Even though the number of flares per patient/year was 0.55, there was variability between patients. Both off-label conventional systemics and off-label biologics were used for flare management without a clear treatment pattern.

Acquired diffuse palmoplantar erythema with keratoderma in Chinese patients with pustular psoriasis: A predictor for IL36 receptor antagonist c.115+6T>C mutation?

Several studies have suggested that mutation of the interleukin 36 receptor antagonist gene (IL36RN) is related to generalized pustular psoriasis (GPP), and the presence of IL36RN mutation may affect the clinical manifestations and treatment responses. However, genetic testing is not routinely available in clinical practice for the diagnosis of GPP. Previously, GPP patients with acrodermatitis continua of Hallopeau (ACH) were found to have a high percentage of carrying IL36RN mutation. In this study, we reported six patients with pustular psoriasis presenting as diffuse palmoplantar erythema with keratoderma among 60 patients who carried IL36RN mutation. ACH was present in five patients and five patients had acute flare of GPP. This unique presentation may serve as a predictor for IL36RN mutation in patients with pustular psoriasis, similar to ACH.

Treatment of Erythrodermic Psoriasis in Children with Secukinumab: A Case Report

Erythrodermic psoriasis (EP) is a rare and severe type of psoriasis. Common systemic therapies for children with EP include treatment with glucocorticoids, cyclosporine, acitretin, and methotrexate. Although these drugs are effective, they may cause serious side effects to children. Secukinumab has recently demonstrated efficacy in treating plaque psoriasis, but its efficacy in EP children remains unknown. We report a case of a seven-year-old patient who transitioned from generalized pustular psoriasis (GPP) to EP after routine systemic drug treatment. The patient was then treated with secukinumab. The patient's condition improved noticeably within 48 hours after the first injection. After the fifth injection, she almost completely cleared her skin lesions and achieved Psoriasis Area and Severity Index 90 (PASI 90) scores. During this period, she experienced only one respiratory infection. She completed all 11 doses of secukinumab by October 14, 2022, with no new rash (PASI 100) and no adverse drug reactions. Follow-up observation on March 15, 2023, showed no new rash (PASI 100) and no adverse reactions after medication withdrawal. This case suggests that it may also be effective in treating children with EP.

A Rare Case of New-Onset Crohn's Disease in a Patient With Chronic Palmoplantar Pustulosis

A 44-year-old woman who had been diagnosed with palmoplantar pustulosis (PPP) at 34 years old was diagnosed with moderate Crohn's disease (CD) based on endoscopic, radiological, and pathological findings. As treatment with corticosteroids, ultraviolet, and cyclosporin had achieved partial response, PPP had been refractory in a chronic continuous state. Oral prednisolone was initially started to treat CD, but clinical remission was not achieved. Intravenous ustekinumab was subsequently started at 260 mg for clinical remission of CD. Eight weeks after starting ustekinumab, clinical remission and mucosal healing were achieved and PPP manifestations on the palms and soles were markedly improved. Ustekinumab appears to offer an effective therapeutic option for patients with PPP but has yet to be approved for this induction in Japan. CD is a rare gastrointestinal involvement in PPP patients that requires attention.

Interleukin-17 vs. Interleukin-23 Inhibitors in Pustular and Erythrodermic Psoriasis: A Retrospective, Multicentre Cohort Study

Pustular and erythrodermic psoriasis are rare and difficult-to-treat conditions. It has recently been shown that interleukin (IL)-17 inhibitors can be very effective among patients with these forms of psoriasis; however, the potential of IL-23 inhibitors is largely unknown. The aim of this multicentre, retrospective study was to compare the safety, effectiveness, and drug survival of IL-17 and IL-23 inhibitors among patients affected by these rare forms of psoriasis. The study involved 27 patients with erythrodermic psoriasis and 59 with pustular psoriasis (36 with generalised pustular psoriasis and 23 with palmoplantar pustular psoriasis) treated with an IL-17 or IL-23 inhibitor. The effectiveness of the two drug classes was assessed using the disease-specific Psoriasis Area Severity Index (PASI) and the Investigator Global Assessment, which were evaluated at different time points. There was a consistent trend towards a higher rate of PASI 100 responses in the patients treated with IL-17 inhibitors compared with those treated with IL-23 inhibitors, and the other efficacy outcomes showed a similar trend. There was no significant between-drug class difference in efficacy at any of the time points in the erythrodermic psoriasis cohort, whereas PASI 90 and PASI 100 response rates were significantly higher among the pustular psoriasis patients receiving IL-17 inhibitors at week 12 (IL-23 19% vs. IL-17 54% and IL-23 6% vs. IL-17 40%, respectively) and the percentage of responders to IL-17 inhibition was significantly higher at week 24 (IL-23 25% vs. IL-17 74%). In conclusion, it is therefore reasonable to assume that IL-17 and IL-23 inhibitors are both effective when treating pustular and erythrodermic psoriasis.

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.

A review of disease burden and clinical management for generalized pustular psoriasis in China

INTRODUCTION

Generalized pustular psoriasis (GPP) is a rare, severe, immune-mediated and potentially life-threatening skin disease. The rarity, differential diagnoses, relapsing nature, skin and systemic symptoms, complications and limited therapeutic approaches for this disease pose a clinical and psychological burden on patients and their families.

AREAS COVERED

Epidemiologic data of GPP in Chinese patients, including the disease prevalence and age of disease onset, as well as epidemiologic data in global populations were reviewed. Multiple proinflammatory cytokines are involved in the disease development and clinical presentation of GPP and the interleukin (IL)-36-mediated signalling pathway play a central role. Furthermore, loss-of-function mutations in IL-36RN (encoding the IL-36 receptor antagonist) are associated with GPP, suggesting a potential drug target for developing a disease-specific therapeutic approach. Biologic agents, including IL-36R targeted agents, are promising treatment options, especially as existing conventional therapies are inadequate. Chinese guidelines for the diagnosis and treatment of psoriasis recommend systemic and topical treatment options for GPP and disease complications, as well as for GPP during pregnancy and juvenile GPP.

EXPERT OPINION

This review summarizes the epidemiology, pathogenesis, clinical characteristics, disease burden and management of patients with GPP in China, and also describes future treatment targets and related clinical trials.

Unmet Educational Needs and Clinical Practice Gaps in the Management of Generalized Pustular Psoriasis: Global Perspectives from the Front Line

INTRODUCTION

Generalized pustular psoriasis (GPP) is a rare, potentially life-threatening, neutrophilic, autoinflammatory skin disease characterised by recurrent flares of generalised sterile pustules and associated systemic features. Inconsistent diagnostic criteria and a lack of approved therapies pose serious challenges to GPP management. Our objectives were to discuss the challenges encountered in the care of patients with GPP and identify healthcare provider (HCP) educational needs and clinical practice gaps in GPP management.

METHODS

On 24 July 2020, 13 dermatologists from 10 countries (Brazil, Canada, China, Egypt, France, Germany, Japan, Malaysia, the UK and the USA) attended a workshop to share experiences in managing patients with GPP. Educational needs and clinical practice gaps grouped according to healthcare system level were discussed and ranked using interactive polling.

RESULTS

Lack of experience of GPP among HCPs was identified as an important individual HCP-level clinical practice gap. Limited understanding of the presentation and pathogenesis of GPP among non-specialists means misdiagnosis is common, delaying referral and treatment. In countries where patients may present to general practitioners or emergency department HCPs, GPP is often mistaken for an infection. Among dermatologists who can accurately diagnose GPP, limited knowledge of treatments may necessitate referral to a colleague with more experience in GPP. At the organisational level, important needs identified were educating emergency department HCPs to recognise GPP as an autoinflammatory disease and improving communication, cooperation and definitions of roles within multidisciplinary teams supporting patients with GPP. At the regulatory level, robust clinical trial data, clear and consistent treatment guidelines and approved therapies were identified as high priorities.

CONCLUSIONS

The educational imperative most consistently identified across the participating countries is for HCPs to understand that GPP can be life-threatening if appropriate treatment initiation is delayed, and to recognise when to refer patients to a colleague with more experience of GPP management.

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.

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.