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.

Single-cell analysis of psoriasis resolution demonstrates an inflammatory fibroblast state targeted by IL-23 blockade

Biologic therapies targeting the IL-23/IL-17 axis have transformed the treatment of psoriasis. However, the early mechanisms of action of these drugs remain poorly understood. Here, we perform longitudinal single-cell RNA-sequencing in affected individuals receiving IL-23 inhibitor therapy. By profiling skin at baseline, day 3 and day 14 of treatment, we demonstrate that IL-23 blockade causes marked gene expression shifts, with fibroblast and myeloid populations displaying the most extensive changes at day 3. We also identify a transient WNT5A+/IL24+ fibroblast state, which is only detectable in lesional skin. In-silico and in-vitro studies indicate that signals stemming from these WNT5A+/IL24+ fibroblasts upregulate multiple inflammatory genes in keratinocytes. Importantly, the abundance of WNT5A+/IL24+ fibroblasts is significantly reduced after treatment. This observation is validated in-silico, by deconvolution of multiple transcriptomic datasets, and experimentally, by RNA in-situ hybridization. These findings demonstrate that the evolution of inflammatory fibroblast states is a key feature of resolving psoriasis skin.

In Silico and In Vitro Analysis of IL36RN Alterations Reveals Critical Residues for the Function of the Interleukin-36 Receptor Complex

Generalized pustular psoriasis is a potentially life-threatening skin disease, associated with IL36RN disease alleles. IL36RN encodes the IL-36 receptor antagonist (IL-36Ra), a protein that downregulates the activity of IL-36 cytokines by blocking their receptor (IL-36R). Although generalized pustular psoriasis can be treated with IL-36R inhibitors, the structural underpinnings of the IL-36Ra/IL-36R interaction remain poorly understood. In this study, we sought to address this question by systematically investigating the effects of IL36RN sequence changes. We experimentally characterized the effects of 30 IL36RN variants on protein stability. In parallel, we used a machinelearning tool (Rhapsody) to analyze the IL-36Ra three-dimensional structure and predict the impact of all possible amino acid substitutions. This integrated approach identified 21 amino acids that are essential for IL-36Ra stability. We next investigated the effects of IL36RN changes on IL-36Ra/IL-36R binding and IL-36R signaling. Combining invitro assays and machine learning with a second program (mCSM), we identified 13 amino acids that are critical for IL-36Ra/IL36R engagement. Finally, we experimentally validated three representative predictions, further confirming the reliability of Rhapsody and mCSM. These findings shed light on the structural determinants of IL-36Ra activity, with potential to facilitate the design of new IL-36 inhibitors and aid the interpretation of IL36RN variants in diagnostic settings.

GWAS meta-analysis of psoriasis identifies new susceptibility alleles impacting disease mechanisms and therapeutic targets

Psoriasis is a common, debilitating immune-mediated skin disease. Genetic studies have identified biological mechanisms of psoriasis risk, including those targeted by effective therapies. However, the genetic liability to psoriasis is not fully explained by variation at robustly identified risk loci. To move towards a saturation map of psoriasis susceptibility we meta-analysed 18 GWAS comprising 36,466 cases and 458,078 controls and identified 109 distinct psoriasis susceptibility loci, including 45 that have not been previously reported. These include susceptibility variants at loci in which the therapeutic targets IL17RA and AHR are encoded, and deleterious coding variants supporting potential new drug targets (including in STAP2, CPVL and POU2F3). We conducted a transcriptome-wide association study to identify regulatory effects of psoriasis susceptibility variants and cross-referenced these against single cell expression profiles in psoriasis-affected skin, highlighting roles for the transcriptional regulation of haematopoietic cell development and epigenetic modulation of interferon signalling in psoriasis pathobiology.

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.

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.

Non-adherence to systemic immune-modifying therapy in people with psoriasis during the COVID-19 pandemic: findings from a global cross-sectional survey

BACKGROUND

Non-adherence to immune-modifying therapy is a complex behaviour which, before the COVID-19 pandemic, was shown to be associated with mental health disorders in people with immune-mediated diseases. The COVID-19 pandemic has led to a rise in the global prevalence of anxiety and depression, and limited data exist on the association between mental health and non-adherence to immune modifying therapy during the pandemic.

OBJECTIVES

To assess the extent of and reasons underlying non-adherence to systemic immune-modifying therapy during the COVID-19 pandemic in individuals with psoriasis, and the association between mental health and non-adherence.

METHODS

Online self-report surveys (PsoProtectMe), including validated screens for anxiety and depression, were completed globally during the first year of the pandemic. We assessed the association between anxiety or depression and non-adherence to systemic immune-modifying therapy using binomial logistic regression, adjusting for potential cofounders (age, sex, ethnicity, comorbidity), and country of residence.

RESULTS

Of 3980 participants from 77 countries, 1611 (40.5%) were prescribed a systemic immune-modifying therapy. Of these, 408 (25.3%) reported non-adherence during the pandemic, most commonly due to concerns about their immunity. In the unadjusted model, a positive anxiety screen was associated with non-adherence to systemic immune-modifying therapy (OR 1.36, 95%CI 1.07-1.76). Specifically, anxiety was associated with non-adherence to targeted therapy (OR 1.41, 95%CI 1.01-1.96) but not standard systemic therapy (OR 1.16, 95%CI 0.81-1.67). In the adjusted model, although the directions of the effects remained, anxiety was not significantly associated with non-adherence to overall systemic (OR 1.20, 95%CI 0.92-1.56) or targeted (OR 1.33, 95%CI 0.94-1.89) immune-modifying therapy. A positive depression screen was not strongly associated with non-adherence to systemic immune-modifying therapy in the unadjusted (OR 1.22, 95% CI 0.94-1.57) or adjusted models (OR 1.14, 95% CI 0.87-1.49).

CONCLUSION

These data indicate substantial non-adherence to immune-modifying therapy in people with psoriasis during the pandemic, with attenuation of the association with mental health after adjusting for confounders. Future research in larger populations should further explore pandemic-specific drivers of treatment non-adherence. Clear communication of the reassuring findings from population-based research regarding immune-modifying therapy-associated adverse COVID-19 risks to people with psoriasis is essential, to optimise adherence and disease outcomes.

Pericarditis and Autoinflammation: A Clinical and Genetic Analysis of Patients With Idiopathic Recurrent Pericarditis and Monogenic Autoinflammatory Diseases at a National Referral Center

Background Idiopathic recurrent pericarditis (IRP) is an orphan disease that carries significant morbidity, partly driven by corticosteroid dependence. Innate immune modulators, colchicine and anti-interleukin-1 agents, pioneered in monogenic autoinflammatory diseases, have demonstrated remarkable efficacy in trials, suggesting that autoinflammation may contribute to IRP. This study characterizes the phenotype of patients with IRP and monogenic autoinflammatory diseases, and establishes whether autoinflammatory disease genes are associated with IRP. Methods and Results We retrospectively analyzed the medical records of patients with IRP (n=136) and monogenic autoinflammatory diseases (n=1910) attending a national center (London, UK) between 2000 and 2021. We examined 4 genes (MEFV, MVK, NLRP3, TNFRSF1A) by next-generation sequencing in 128 patients with IRP and compared the frequency of rare deleterious variants to controls obtained from the Genome Aggregation Database. In this cohort of patients with IRP, corticosteroid dependence was common (39/136, 28.7%) and was associated with chronic pain (adjusted odds ratio 2.8 [95% CI, 1.3-6.5], P=0.012). IRP frequently manifested with systemic inflammation (raised C-reactive protein [121/136, 89.0%] and extrapericardial effusions [68/136, 50.0%]). Pericarditis was observed in all examined monogenic autoinflammatory diseases (0.4%-3.7% of cases). Rare deleterious MEFV variants were more frequent in IRP than in ancestry-matched controls (allele frequency 9/200 versus 2932/129 200, P=0.040). Conclusions Pericarditis is a feature of interleukin-1 driven monogenic autoinflammatory diseases and IRP is associated with variants in MEFV, a gene involved in interleukin-1β processing. We also found that corticosteroid dependence in IRP is associated with chronic noninflammatory pain. Together these data implicate autoinflammation in IRP and support reducing reliance on corticosteroids in its management.

Differences in Clinical Features and Comorbid Burden between HLA-C∗06:02 Carrier Groups in >9,000 People with Psoriasis

The identification of robust endotypes-disease subgroups of clinical relevance-is fundamental to stratified medicine. We hypothesized that HLA-C∗06:02 status, the major genetic determinant of psoriasis, defines a psoriasis endotype of clinical relevance. Using two United Kingdom-based cross-sectional datasets-an observational severe-psoriasis study (Biomarkers of Systemic Treatment Outcomes in Psoriasis; n = 3,767) and a large population-based bioresource (UK Biobank, including n = 5,519 individuals with psoriasis)-we compared demographic, environmental, and clinical variables of interest in HLA-C∗06:02-positive (one or two copies of the HLA-C∗06:02 allele) with those in HLA-C∗06:02‒negative (no copies) individuals of European ancestry. We used multivariable regression analyses to account for mediation effects established a priori. We confirm previous observations that HLA-C∗06:02-positive status is associated with earlier age of psoriasis onset and extend findings to reveal an association with disease expressivity in females (Biomarkers of Systemic Treatment Outcomes in Psoriasis: P = 2.7 × 10-14, UK Biobank: P = 1.0 × 10-8). We also show HLA-C∗06:02-negative status to be associated with characteristic clinical features (large plaque disease, OR for HLA-C∗06:02 = 0.73, P = 7.4 × 10-4; nail involvement, OR = 0.70, P = 2.4 × 10-6); higher central adiposity (Biomarkers of Systemic Treatment Outcomes in Psoriasis: waist circumference difference of 2.0 cm, P = 8.4 × 10-4; UK Biobank: waist circumference difference of 1.4 cm, P = 1.5 × 10-4), especially in women; and a higher prevalence of other cardiometabolic comorbidities. These findings extend the clinical phenotype delineated by HLA-C∗06:02 and highlight its potential as an important biomarker to consider in future multimarker stratified medicine approaches.

Single-cell analysis implicates Th17 to Th2 cell plasticity in the pathogenesis of palmoplantar pustulosis

BACKGROUND

Palmoplantar pustulosis (PPP) is a severe inflammatory skin disorder, characterised by eruptions of painful, neutrophil-filled pustules on the palms and soles. While PPP has a profound effect on quality of life, it remains poorly understood and notoriously difficult to treat.

OBJECTIVE

We sought to investigate the immune pathways that underlie the pathogenesis of PPP.

METHODS

We applied bulk- and single-cell RNA-sequencing methods to the analysis of skin biopsies and peripheral blood mononuclear cells. We validated our results by flow cytometry and immune fluorescence microscopy RESULTS: Bulk RNA-sequencing of patient skin detected an unexpected signature of T-cell activation, with a significant overexpression of several Th2 genes typically upregulated in atopic dermatitis. To further explore these findings, we carried out single-cell RNA-sequencing in peripheral blood mononuclear cells of healthy and affected individuals. We found that the memory CD4+T-cells of PPP patients were skewed towards a Th17 phenotype, a phenomenon that was particularly significant among CLA+ skin-homing cells. We also identified a subset of memory CD4+ T-cells which expressed both Th17 (KLRB1/CD161) and Th2 (GATA3) markers, with pseudo-time analysis suggesting that the population was the result of Th17 to Th2 plasticity. Interestingly, the GATA3+/CD161+ cells were over-represented among the PBMCs of affected individuals, both in the scRNA-seq dataset and in independent flow-cytometry experiments. Dual positive cells were also detected in patient skin by means of immune fluorescence microscopy.

CONCLUSIONS

These observations demonstrate that PPP is associated with complex T-cell activation patterns and may explain why biologics that target individual T-helper populations have shown limited therapeutic efficacy.

CLINICAL IMPLICATIONS

The simultaneous activation of Th17 and Th2 responses in PPP supports the therapeutic use of agents that inhibit multiple T-cell pathways.

Genetic analysis of NLRP3 in recurrent pericarditis

Background

The mechanisms underlying recurrent pericarditis are poorly understood, although the efficacy of colchicine and targeted inhibitors of the interleukin-1 pathway implicate auto-inflammation in its pathogenesis. NLRP3 (NACHT, leucine-rich repeat, and pyrin domain containing protein 3) forms part of the NLRP3 inflammasome that mediates post-translational processing of interleukin-1, and colchicine has also been demonstrated to inhibit this pathway. Pathogenic mutations in exon 3 of NLRP3 cause the auto-inflammatory disease cryopyrin associated periodic syndrome, and the management of this disease and other auto-inflammatory diseases has been transformed over the last two decades by the use of targeted anti-interleukin-1 agents. More recently, NLRP3 inflammasome activity has been demonstrated to be upregulated in the pericardia of patients with recurrent pericarditis.

Purpose

Given that mutations in exon 3 of NLRP3 are known to cause auto-inflammatory disease and NLRP3 activity is implicated in recurrent pericarditis, we undertook a genetic analysis of exon 3 of NLRP3 in 99 patients with recurrent pericarditis to determine whether pathogenic mutations in this gene are associated with the disease.

Methods

Exon 3 of NLRP3 was analysed either by Sanger (n=30) or amplicon-based next generation (n=69) sequencing. Variants identified by next generation sequencing were validated by Sanger sequencing. Minor allele frequencies were compared to those in the healthy reference population in the Genome Aggregation database (gnomAD) using Fisher's exact test. p values <0.05 were considered statistically significant.

Results

No known pathogenic mutations in exon 3 of NLRP3 were identified in 99 patients with recurrent pericarditis. Three patients harboured variants of unknown significance (V198M, T543M, Q703K) in NLRP3. A burden association test comparing the combined frequency of all variants in exon 3 of NLRP3 in this cohort against that observed in healthy controls in gnomAD found no significant difference in allele frequency.

Conclusions

This is the first reported genetic analysis of NLRP3 in a cohort of patients with recurrent pericarditis and found no evidence to implicate mutations in this gene in the disease. Whilst access to effective therapies for pericarditis is widening, decisions on treatment duration and identification of patients at risk of recurrent or treatment refractory disease remain significant clinical challenges. Further work exploring the mechanisms by which NLRP3 activity is upregulated in recurrent pericarditis is therefore indicated to identify biomarkers of disease activity and to stratify patients at risk of recurrence. Given the recent successes of agents targeting this pathway in coronary artery disease in clinical trials, such studies may also provide important insights that are of wider interest to the field of cardiovascular medicine.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Clinical Research Training Fellowship

Anakinra for palmoplantar pustulosis: results from a randomized, double-blind, multicentre, two-staged, adaptive placebo-controlled trial (APRICOT)

BACKGROUND

Palmoplantar pustulosis (PPP) is a rare, debilitating, chronic inflammatory skin disease that affects the hands and feet. Clinical, immunological and genetic findings suggest a pathogenic role for interleukin (IL)-1.

OBJECTIVES

To determine whether anakinra (an IL-1 receptor antagonist) delivers therapeutic benefit in PPP.

METHODS

This was a randomized (1 : 1), double-blind, two-staged, adaptive, UK multicentre, placebo-controlled trial [ISCRTN13127147 (registered 1 August 2016); EudraCT number: 2015-003600-23 (registered 1 April 2016)]. Participants had a diagnosis of PPP (> 6 months) requiring systemic therapy. Treatment was 8 weeks of anakinra or placebo via daily, self-administered subcutaneous injections. Primary outcome was the Palmoplantar Pustulosis Psoriasis Area and Severity Index (PPPASI) at 8 weeks.

RESULTS

A total of 374 patients were screened; 64 were enrolled (31 in the anakinra arm and 33 in the placebo arm) with a mean (SD) baseline PPPASI of 17·8 (10·5) and a PPP investigator's global assessment of severe (50%) or moderate (50%). The baseline adjusted mean difference in PPPASI favoured anakinra but did not demonstrate superiority in the intention-to-treat analysis [-1·65, 95% confidence interval (CI) -4·77 to 1·47; P = 0·30]. Similarly, secondary objective measures, including fresh pustule count (2·94, 95% CI -26·44 to 32·33; favouring anakinra), total pustule count (-30·08, 95% CI -83·20 to 23·05; favouring placebo) and patient-reported outcomes, did not show superiority of anakinra. When modelling the impact of adherence, the PPPASI complier average causal effect for an individual who received ≥ 90% of the total treatment (48% in the anakinra group) was -3·80 (95% CI -10·76 to 3·16; P = 0·285). No serious adverse events occurred.

CONCLUSIONS

No evidence for the superiority of anakinra was found. IL-1 blockade is not a useful intervention for the treatment of PPP.

Risk-mitigating behaviours in people with inflammatory skin and joint disease during the COVID-19 pandemic differ by treatment type: a cross-sectional patient survey

BACKGROUND

Registry data suggest that people with immune-mediated inflammatory diseases (IMIDs) receiving targeted systemic therapies have fewer adverse coronavirus disease 2019 (COVID-19) outcomes compared with patients receiving no systemic treatments.

OBJECTIVES

We used international patient survey data to explore the hypothesis that greater risk-mitigating behaviour in those receiving targeted therapies may account, at least in part, for this observation.

METHODS

Online surveys were completed by individuals with psoriasis (globally) or rheumatic and musculoskeletal diseases (RMDs) (UK only) between 4 May and 7 September 2020. We used multiple logistic regression to assess the association between treatment type and risk-mitigating behaviour, adjusting for clinical and demographic characteristics. We characterized international variation in a mixed-effects model.

RESULTS

Of 3720 participants (2869 psoriasis, 851 RMDs) from 74 countries, 2262 (60·8%) reported the most stringent risk-mitigating behaviour (classified here under the umbrella term 'shielding'). A greater proportion of those receiving targeted therapies (biologics and Janus Kinase inhibitors) reported shielding compared with those receiving no systemic therapy [adjusted odds ratio (OR) 1·63, 95% confidence interval (CI) 1·35-1·97]. The association between targeted therapy and shielding was preserved when standard systemic therapy was used as the reference group (OR 1·39, 95% CI 1·23-1·56). Shielding was associated with established risk factors for severe COVID-19 [male sex (OR 1·14, 95% CI 1·05-1·24), obesity (OR 1·37, 95% CI 1·23-1·54), comorbidity burden (OR 1·43, 95% CI 1·15-1·78)], a primary indication of RMDs (OR 1·37, 95% CI 1·27-1·48) and a positive anxiety or depression screen (OR 1·57, 95% CI 1·36-1·80). Modest differences in the proportion shielding were observed across nations.

CONCLUSIONS

Greater risk-mitigating behaviour among people with IMIDs receiving targeted therapies may contribute to the reported lower risk of adverse COVID-19 outcomes. The behaviour variation across treatment groups, IMIDs and nations reinforces the need for clear evidence-based patient communication on risk-mitigation strategies and may help inform updated public health guidelines as the pandemic continues.

Factors associated with adverse COVID-19 outcomes in patients with psoriasis-insights from a global registry-based study

BACKGROUND

The multimorbid burden and use of systemic immunosuppressants in people with psoriasis may confer greater risk of adverse outcomes of coronavirus disease 2019 (COVID-19), but the data are limited.

OBJECTIVE

Our aim was to characterize the course of COVID-19 in patients with psoriasis and identify factors associated with hospitalization.

METHODS

Clinicians reported patients with psoriasis with confirmed/suspected COVID-19 via an international registry, Psoriasis Patient Registry for Outcomes, Therapy and Epidemiology of COVID-19 Infection. Multiple logistic regression was used to assess the association between clinical and/or demographic characteristics and hospitalization. A separate patient-facing registry characterized risk-mitigating behaviors.

RESULTS

Of 374 clinician-reported patients from 25 countries, 71% were receiving a biologic, 18% were receiving a nonbiologic, and 10% were not receiving any systemic treatment for psoriasis. In all, 348 patients (93%) were fully recovered from COVID-19, 77 (21%) were hospitalized, and 9 (2%) died. Increased hospitalization risk was associated with older age (multivariable-adjusted odds ratio [OR] = 1.59 per 10 years; 95% CI = 1.19-2.13), male sex (OR = 2.51; 95% CI = 1.23-5.12), nonwhite ethnicity (OR = 3.15; 95% CI = 1.24-8.03), and comorbid chronic lung disease (OR = 3.87; 95% CI = 1.52-9.83). Hospitalization was more frequent in patients using nonbiologic systemic therapy than in those using biologics (OR = 2.84; 95% CI = 1.31-6.18). No significant differences were found between classes of biologics. Independent patient-reported data (n = 1626 across 48 countries) suggested lower levels of social isolation in individuals receiving nonbiologic systemic therapy than in those receiving biologics (OR = 0.68; 95% CI = 0.50-0.94).

CONCLUSION

In this international case series of patients with moderate-to-severe psoriasis, biologic use was associated with lower risk of COVID-19-related hospitalization than with use of nonbiologic systemic therapies; however, further investigation is warranted on account of potential selection bias and unmeasured confounding. Established risk factors (being older, being male, being of nonwhite ethnicity, and having comorbidities) were associated with higher hospitalization rates.

Association of Clinical and Demographic Factors With the Severity of Palmoplantar Pustulosis

Importance

Although palmoplantar pustulosis (PPP) can significantly impact quality of life, the factors underlying disease severity have not been studied.

Objective

To examine the factors associated with PPP severity.

Design, Setting, and Participants

An observational, cross-sectional study of 2 cohorts was conducted. A UK data set including 203 patients was obtained through the Anakinra in Pustular Psoriasis, Response in a Controlled Trial (2016-2019) and its sister research study Pustular Psoriasis, Elucidating Underlying Mechanisms (2016-2020). A Northern European cohort including 193 patients was independently ascertained by the European Rare and Severe Psoriasis Expert Network (2014-2017). Patients had been recruited in secondary or tertiary dermatology referral centers. All patients were of European descent. The PPP diagnosis was established by dermatologists, based on clinical examination and/or published consensus criteria. The present study was conducted from October 1, 2014, to March 15, 2020.

Main Outcomes and Measures

Demographic characteristics, comorbidities, smoking status, Palmoplantar Pustulosis Psoriasis Area Severity Index (PPPASI), measuring severity from 0 (no sign of disease) to 72 (very severe disease), or Physician Global Assessment (PGA), measuring severity as 0 (clear), 1 (almost clear), 2 (mild), 3 (moderate), and 4 (severe).

Results

Among the 203 UK patients (43 men [21%], 160 women [79%]; median age at onset, 48 [interquartile range (IQR), 38-59] years), the PPPASI was inversely correlated with age of onset (r = -0.18, P = .01). Similarly, in the 159 Northern European patients who were eligible for inclusion in this analysis (25 men [16%], 134 women [84%]; median age at onset, 45 [IQR, 34-53.3] years), the median age at onset was lower in individuals with a moderate to severe PGA score (41 years [IQR, 30.5-52 years]) compared with those with a clear to mild PGA score (46.5 years [IQR, 35-55 years]) (P = .04). In the UK sample, the median PPPASI score was higher in women (9.6 [IQR, 3.0-16.2]) vs men (4.0 [IQR, 1.0-11.7]) (P = .01). Likewise, moderate to severe PPP was more prevalent among Northern European women (57 of 134 [43%]) compared with men (5 of 25 [20%]) (P = .03). In the UK cohort, the median PPPASI score was increased in current smokers (10.7 [IQR, 4.2-17.5]) compared with former smokers (7 [IQR, 2.0-14.4]) and nonsmokers (2.2 [IQR, 1-6]) (P = .003). Comparable differences were observed in the Northern European data set, as the prevalence of moderate to severe PPP was higher in former and current smokers (51 of 130 [39%]) compared with nonsmokers (6 of 24 [25%]) (P = .14).

Conclusions and Relevance

The findings of this study suggest that PPP severity is associated with early-onset disease, female sex, and smoking status. Thus, smoking cessation intervention might be beneficial.

Loss-of-Function Myeloperoxidase Mutations Are Associated with Increased Neutrophil Counts and Pustular Skin Disease

The identification of disease alleles underlying human autoinflammatory diseases can provide important insights into the mechanisms that maintain neutrophil homeostasis. Here, we focused our attention on generalized pustular psoriasis (GPP), a potentially life-threatening disorder presenting with cutaneous and systemic neutrophilia. Following the whole-exome sequencing of 19 unrelated affected individuals, we identified a subject harboring a homozygous splice-site mutation (c.2031-2A>C) in MPO. This encodes myeloperoxidase, an essential component of neutrophil azurophil granules. MPO screening in conditions phenotypically related to GPP uncovered further disease alleles in one subject with acral pustular psoriasis (c.2031-2A>C;c.2031-2A>C) and in two individuals with acute generalized exanthematous pustulosis (c.1705C>T;c.2031-2A>C and c.1552_1565del;c.1552_1565del). A subsequent analysis of UK Biobank data demonstrated that the c.2031-2A>C and c.1705C>T (p.Arg569Trp) disease alleles were also associated with increased neutrophil abundance in the general population (p = 5.1 × 10^-6 and p = 3.6 × 10^-5, respectively). The same applied to three further deleterious variants that had been genotyped in the cohort, with two alleles (c.995C>T [p.Ala332Val] and c.752T>C [p.Met251Thr]) yielding p values < 10^-10. Finally, treatment of healthy neutrophils with an MPO inhibitor (4-Aminobenzoic acid hydrazide) increased cell viability and delayed apoptosis, highlighting a mechanism whereby MPO mutations affect granulocyte numbers. These findings identify MPO as a genetic determinant of pustular skin disease and neutrophil abundance. Given the recent interest in the development of MPO antagonists for the treatment of neurodegenerative disease, our results also suggest that the pro-inflammatory effects of these agents should be closely monitored.

A randomised placebo controlled trial of anakinra for treating pustular psoriasis: statistical analysis plan for stage two of the APRICOT trial

BACKGROUND

Current treatment options for Palmoplantar Pustulosis (PPP), a debilitating chronic skin disease which affects the hands and feet, are limited. The Anakinra for Pustular psoriasis: Response in a Controlled Trial (APRICOT) aims to determine the efficacy of anakinra in the treatment of PPP. This article describes the statistical analysis plan for the final analysis of this two-staged trial, which was determined prior to unblinding and database lock. This is an update to the published protocol and stage one analysis plan.

METHODS

APRICOT is a randomised, double-blind, placebo-controlled trial of anakinra versus placebo, with two stages and an adaptive element. Stage one compared treatment arms to ensure proof-of-concept and determined the primary outcome for stage two of the trial. The primary outcome was selected to be the change in Palmoplantar Pustulosis Psoriasis Area and Severity Index (PPPASI) at 8 weeks. Secondary outcomes include other investigator-assessed efficacy measures of disease severity, participant-reported measures of efficacy and safety measures. This manuscript describes in detail the outcomes, sample size, general analysis principles, the pre-specified statistical analysis plan for each of the outcomes, the handling of missing outcome data and the planned sensitivity and supplementary analyses for the second stage of the APRICOT trial.

DISCUSSION

This statistical analysis plan was developed in compliance with international trial guidelines and is published to increase transparency of the trial analysis. The results of the trial analysis will indicate whether anakinra has a role in the treatment of PPP.

TRIAL REGISTRATION

ISCRTN, ISCRTN13127147. Registered on 1 August 2016. EudraCT Number 2015-003600-23. Registered on 1 April 2016.

Psoriasis and Genetics

Psoriasis is a common inflammatory skin disease caused by the interplay between multiple genetic and environmental risk factors. This review summarises recent progress in elucidating the genetic basis of psoriasis, particularly through large genome-wide association studies. We illustrate the power of genetic analyses for disease stratification. Psoriasis can be stratified by phenotype (common plaque versus rare pustular variants), or by outcome (prognosis, comorbidities, response to treatment); recent progress has been made in delineating the genetic contribution in each of these areas. We also highlight how genetic data can directly inform the development of effective psoriasis treatments.

IL-36 Promotes Systemic IFN-I Responses in Severe Forms of Psoriasis

Psoriasis is an immune-mediated skin disorder associated with severe systemic comorbidities. Whereas IL-36 is a key disease driver, the pathogenic role of this cytokine has mainly been investigated in skin. Thus, its effects on systemic immunity and extracutaneous disease manifestations remain poorly understood. To address this issue, we investigated the consequences of excessive IL-36 activity in circulating immune cells. We initially focused our attention on generalized pustular psoriasis (GPP), a clinical variant associated with pervasive upregulation of IL-36 signaling. By undertaking blood and neutrophil RNA sequencing, we demonstrated that affected individuals display a prominent IFN-I signature, which correlates with abnormal IL-36 activity. We then validated the association between IL-36 deregulation and IFN-I over-expression in patients with severe psoriasis vulgaris (PV). We also found that the activation of IFN-I genes was associated with extracutaneous morbidity, in both GPP and PV. Finally, we undertook mechanistic experiments, demonstrating that IL-36 acts directly on plasmacytoid dendritic cells, where it potentiates toll-like receptor (TLR)-9 activation and IFN-α production. This effect was mediated by the upregulation of PLSCR1, a phospholipid scramblase mediating endosomal TLR-9 translocation. These findings identify an IL-36/ IFN-I axis contributing to extracutaneous inflammation in psoriasis.

A small population, randomised, placebo-controlled trial to determine the efficacy of anakinra in the treatment of pustular psoriasis: study protocol for the APRICOT trial

Background

Palmoplantar pustulosis is a rare but painful and debilitating disease. It consistently ranks the highest of all psoriasis phenotypic variants in terms of symptoms and functional impairment. Management of plaque-type psoriasis has been revolutionised in the last 10 years with the advent of biologic therapies, but treatment options for pustular psoriasis remain profoundly limited. On the basis of mechanistic findings which suggest a key pathogenic role for interleukin (IL)-1 in pustular psoriasis, we hypothesise that anakinra (IL-1 blockade) will be an efficacious treatment for pustular psoriasis.

Methods/design

We will conduct a two-stage, adaptive, double-blind, randomised, placebo-controlled trial to test the hypothesis that anakinra, self-administered daily by subcutaneous injection over 8 weeks, will deliver therapeutic benefit in palmoplantar pustular psoriasis, a localised form of pustular psoriasis typically involving the palms and/or soles. Safety outcomes will be collected for 20 weeks. A total of 64 participants will be randomised to anakinra or placebo in a 1:1 ratio. At the end of stage 1, a decision to progress to stage 2 will be made. This decision will take place after 24 participants have been randomised and followed for 8 weeks and will be based on the ordering of the observed mean outcome values in both treatment arms. At the end of stage 1, the reliability of outcome measurements and method to collect the data will also be assessed, and the primary outcome will be confirmed for stage 2.

Discussion

We have undertaken an adaptive approach in which we will gain proof-of-concept data prior to completing a powered efficacy trial because pustular psoriasis is a rare disease, no validated outcome measures to detect change exist, and limited safety data for anakinra exist in this population. To our knowledge, this will be the first randomised controlled trial that will provide valuable evidence for the efficacy and safety of IL-1 blockade for treatment in pustular psoriasis.

Trial registration

ISRCTN13127147. Registered on 1st August 2016.

EudraCT, 2015-003600-23. Registered on 1st April 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2841-y) contains supplementary material, which is available to authorized users.

An analysis of IL-36 signature genes and individuals with IL1RL2 knockout mutations validates IL-36 as a psoriasis therapeutic target

Interleukin (IL)-36α, IL-36β, and IL-36γ are innate mediators of acute epithelial inflammation. We sought to demonstrate that these cytokines are also required for the pathogenesis of plaque psoriasis, a common and chronic skin disorder, caused by abnormal T helper 17 (T_H17) cell activation. To investigate this possibility, we first defined the genes that are induced by IL-36 cytokines in primary human keratinocytes. This enabled us to demonstrate a significant IL-36 signature among the transcripts that are up-regulated in plaque psoriasis and the susceptibility loci associated with the disease in genome-wide studies. Next, we investigated the impact of in vivo and ex vivo IL-36 receptor blockade using a neutralizing antibody or a recombinant antagonist. Both inhibitors had marked anti-inflammatory effects on psoriatic skin, demonstrated by statistically significant reductions in IL-17 expression, keratinocyte activation, and leukocyte infiltration. Finally, we explored the potential safety profile associated with IL-36 blockade by phenotyping 12 individuals carrying knockout mutations of the IL-36 receptor gene. We found that normal immune function was broadly preserved in these individuals, suggesting that IL-36 signaling inhibition would not substantially compromise host defenses. These observations, which integrate the results of transcriptomics and model system analysis, pave the way for early-stage clinical trials of IL-36 antagonists.

Exome-wide association study reveals novel psoriasis susceptibility locus at TNFSF15 and rare protective alleles in genes contributing to type I IFN signalling

Psoriasis is a common inflammatory skin disorder for which multiple genetic susceptibility loci have been identified, but few resolved to specific functional variants. In this study, we sought to identify common and rare psoriasis-associated gene-centric variation. Using exome arrays we genotyped four independent cohorts, totalling 11 861 psoriasis cases and 28 610 controls, aggregating the dataset through statistical meta-analysis. Single variant analysis detected a previously unreported risk locus at TNFSF15 (rs6478108; P = 1.50 × 10-8, OR = 1.10), and association of common protein-altering variants at 11 loci previously implicated in psoriasis susceptibility. We validate previous reports of protective low-frequency protein-altering variants within IFIH1 (encoding an innate antiviral receptor) and TYK2 (encoding a Janus kinase), in each case establishing a further series of protective rare variants (minor allele frequency < 0.01) via gene-wide aggregation testing (IFIH1: pburden = 2.53 × 10-7, OR = 0.707; TYK2: pburden = 6.17 × 10-4, OR = 0.744). Both genes play significant roles in type I interferon (IFN) production and signalling. Several of the protective rare and low-frequency variants in IFIH1 and TYK2 disrupt conserved protein domains, highlighting potential mechanisms through which their effect may be exerted.

European consensus statement on phenotypes of pustular psoriasis

Pustular psoriasis (PP) is a group of inflammatory skin conditions characterized by infiltration of neutrophil granulocytes in the epidermis to such an extent that clinically visible sterile pustules develop. Because of clinical co-incidence, PP is currently grouped with psoriasis vulgaris (PV). However, PP and PV are phenotypically different, respond differently to treatments and seem to be distinct on the genetic level. In contrast to PV, the phenotypes of PP are not well defined. Descriptions of each form of PP are discordant among standard dermatology textbooks [Saurat Dermatologie 2016, Rook's Dermatology 2016, Fitzpatrick's 2012 and Braun-Falco 2012], encumbering the collection of phenotypically well-matched groups of patients as well as clinical trials. The European Rare and Severe Psoriasis Expert Network (ERASPEN) was founded to define consensus criteria for diagnosis, deeply phenotype large groups of PP patients, analyse the genetics and pathophysiology and prepare for prospective clinical trials. This work reviews historical aspects of these conditions, new genetic findings and presents our initial considerations on the phenotypes of PP and a consensus classification of clinical phenotypes that will be used as a baseline for further, prospective studies of PP. Generalized pustular psoriasis (GPP) is defined as primary, sterile, macroscopically visible pustules on non-acral skin (excluding cases where pustulation is restricted to psoriatic plaques). GPP can occur with or without systemic inflammation, with or without PV and can either be a relapsing (>1 episode) or persistent (>3 months) condition. Acrodermatitis continua of Hallopeau (ACH) is characterized by primary, persistent (>3 months), sterile, macroscopically visible pustules affecting the nail apparatus. Palmoplantar pustulosis (PPP) has primary, persistent (>3 months), sterile, macroscopically visible pustules on palms and/or soles and can occur with or without PV.

Juvenile generalized pustular psoriasis is a chronic recalcitrant disease: an analysis of 27 patients seen in a tertiary hospital in Johor, Malaysia

BACKGROUND

Limited information exists regarding juvenile generalized pustular psoriasis (GPP). We aim to determine the clinical profile and outcome of Malaysians with juvenile GPP.

METHODS

Review of hospital case notes on patients with juvenile GPP.

RESULTS

Twenty-seven patients with juvenile GPP were identified. Female to male ratio was 1.4:1. The median age at onset of GPP was 6.5 years. Ten patients had prior psoriasis with a median pre-pustular duration of 2.7 years. Onset of GPP was earlier in patients without prior psoriasis (5.1 years vs. 12.0 years, P = 0.002). Precipitating factors identified included stress, upper respiratory tract infection, systemic steroid use, vaccination, and pregnancy. A positive family history of psoriasis and GPP was present in six and one patient(s), respectively. Twenty-one patients had acute, five annular, and one localized variant of GPP. Arthritis was present in 22.2%. Fever, leukocytosis, and transaminitis were mainly seen in patients with acute GPP at 80.9, 72.2, and 11.1%, respectively. Among 20 patients screened, eight carry IL36RN variants and one has CARD14 mutation. IL36RN-positive patients have more severe disease characterized by early onset, low prevalence of prior plaque psoriasis, high prevalence of systemic inflammation, and need for continuous long-term systemic therapy. Acitretin and cyclosporine were effective in aborting acute GPP in 100% of 16 and 66.7% of six patients treated, respectively. However, relapses were common. Only three of the 17 patients whose initial acute GPP was controlled with systemic agents were successfully weaned off treatment.

CONCLUSIONS

Juvenile GPP is a chronic recalcitrant disease. IL36RN-positive patients have more severe disease.

AP1S3 Mutations Cause Skin Autoinflammation by Disrupting Keratinocyte Autophagy and Up-Regulating IL-36 Production

Prominent skin involvement is a defining characteristic of autoinflammatory disorders caused by abnormal IL-1 signaling. However, the pathways and cell types that drive cutaneous autoinflammatory features remain poorly understood. We sought to address this issue by investigating the pathogenesis of pustular psoriasis, a model of autoinflammatory disorders with predominant cutaneous manifestations. We specifically characterized the impact of mutations affecting AP1S3, a disease gene previously identified by our group and validated here in a newly ascertained patient resource. We first showed that AP1S3 expression is distinctively elevated in keratinocytes. Because AP1S3 encodes a protein implicated in autophagosome formation, we next investigated the effects of gene silencing on this pathway. We found that AP1S3 knockout disrupts keratinocyte autophagy, causing abnormal accumulation of p62, an adaptor protein mediating NF-κB activation. We showed that as a consequence, AP1S3-deficient cells up-regulate IL-1 signaling and overexpress IL-36α, a cytokine that is emerging as an important mediator of skin inflammation. These abnormal immune profiles were recapitulated by pharmacological inhibition of autophagy and verified in patient keratinocytes, where they were reversed by IL-36 blockade. These findings show that keratinocytes play a key role in skin autoinflammation and identify autophagy modulation of IL-36 signaling as a therapeutic target.

Update on psoriasis immunopathogenesis and targeted immunotherapy

Over recent years, significant progress has been made in characterisation of the underlying pathogenic mechanisms in psoriasis, a common cutaneous disease that is associated with major systemic co-morbidity and reduced life expectancy. Basic science discoveries have informed the design of novel therapeutic approaches, many of which are now under evaluation in late-stage clinical trials. Here we describe the complex interplay between immune cell types and cytokine networks that acts within self-perpetuating feedback loops to drive cutaneous inflammation in psoriasis. Genetic studies have been pivotal in the construction of the disease model and more recently have uncovered a distinct aetiology for rare, pustular variants of psoriasis. The translation of mechanistic insights into potential advancements in clinical care will also be described, including several treatments that target the interleukin-23 (IL-23)/T17 immune axis.

Genetics of psoriasis

Psoriasis is a common and debilitating immune-mediated skin disease with a complex genetic basis. Genetic studies have provided critical insights into the pathogenesis of disease. This article focuses on the results of genetic association studies, which provide evidence that psoriasis susceptibility genes are involved in innate and adaptive immunity and skin barrier functions. The potential for disease stratification and the development of more effective treatments with fewer side effects using genetic data are highlighted.

Enhanced meta-analysis and replication studies identify five new psoriasis susceptibility loci

Psoriasis is a chronic autoimmune disease with complex genetic architecture. Previous genome-wide association studies (GWAS) and a recent meta-analysis using Immunochip data have uncovered 36 susceptibility loci. Here, we extend our previous meta-analysis of European ancestry by refined genotype calling and imputation and by the addition of 5,033 cases and 5,707 controls. The combined analysis, consisting of over 15,000 cases and 27,000 controls, identifies five new psoriasis susceptibility loci at genome-wide significance (P<5 × 10(-8)). The newly identified signals include two that reside in intergenic regions (1q31.1 and 5p13.1) and three residing near PLCL2 (3p24.3), NFKBIZ (3q12.3) and CAMK2G (10q22.2). We further demonstrate that NFKBIZ is a TRAF3IP2-dependent target of IL-17 signalling in human skin keratinocytes, thereby functionally linking two strong candidate genes. These results further integrate the genetics and immunology of psoriasis, suggesting new avenues for functional analysis and improved therapies.

AP1S3 mutations are associated with pustular psoriasis and impaired Toll-like receptor 3 trafficking

Adaptor protein complex 1 (AP-1) is an evolutionary conserved heterotetramer that promotes vesicular trafficking between the trans-Golgi network and the endosomes. The knockout of most murine AP-1 complex subunits is embryonically lethal, so the identification of human disease-associated alleles has the unique potential to deliver insights into gene function. Here, we report two founder mutations (c.11T>G [p.Phe4Cys] and c.97C>T [p.Arg33Trp]) in AP1S3, the gene encoding AP-1 complex subunit σ1C, in 15 unrelated individuals with a severe autoinflammatory skin disorder known as pustular psoriasis. Because the variants are predicted to destabilize the 3D structure of the AP-1 complex, we generated AP1S3-knockdown cell lines to investigate the consequences of AP-1 deficiency in skin keratinocytes. We found that AP1S3 silencing disrupted the endosomal translocation of the innate pattern-recognition receptor TLR-3 (Toll-like receptor 3) and resulted in a marked inhibition of downstream signaling. These findings identify pustular psoriasis as an autoinflammatory phenotype caused by defects in vesicular trafficking and demonstrate a requirement of AP-1 for Toll-like receptor homeostasis.