Pyoderma Gangrenosum: A Systematic Review of the Molecular Characteristics of Disease

Disrupted Redox Regulation and Inflammatory Response in Pyoderma Gangrenosum

INTRODUCTION

The pathophysiology of Pyoderma Gangrenosum (PG) involves altered innate and adaptive immunity, mutagenic and epigenetic changes, the autoinflammatory state, and the overexpression of cytokines. This study investigated the potential contribution of inflammation, redox signaling, and the immune system in the pathogenesis of PG.

MATERIALS AND METHODS

This case-control study included 36 patients with PG and 30 controls. We have determined the serum concentrations of acute phase proteins (C-reactive protein-CRP, alpha1 glycoprotein acid-AGPA, Albumin), interleukin-17A -IL-17A, β2 microglobulin-β2MG, reduced glutathione-GSH, oxidized glutathione- GSSG, the GSH/GSSG ratio, and hematological parameters (white blood cells-WBC, neutrophil-lymphocyte ratio-NLR, erythrocyte sedimentation rate-ESR) in patients with PG compared with controls. Furthermore, we have evaluated the variations in these markers before and after treatment in PG patients.

RESULTS

The serum concentrations of acute phase proteins (CRP, AGPA, and Albumin) and the IL-17A, β2MG, GSH, GSSG, and GSH/GSSG ratio were significantly different between the PG group and controls. Hematological parameters (WBC, NLR, and ESR), acute phase proteins (CRP, AGPA, and albumin), and IL-17A showed an exaggerated and persistent inflammatory response in patients with PG. In patients with PG associated with systemic diseases, the dysregulation of the biochemical events was more severe.

CONCLUSIONS

The acute phase proteins, β2MG-MHC class I complex, and the GSH-GSSG system are unbalanced in PG. Our results could improve the diagnosis and our understanding of the pathogenic basis of PG.

Keratin Variants in Pyoderma Gangrenosum: Pathogenetic Insights from a Whole-Exome Sequencing-Based Bioinformatic Analysis

Pyoderma gangrenosum (PG) is an inflammatory skin disorder that belongs to the group of neutrophilic dermatoses. Clinically, it is typified by cutaneous ulcers with distinctive erythematoviolaceous borders and may occur alone or in association with other inflammatory, autoinflammatory, or neoplastic conditions. Although its pathophysiology remains incompletely understood, mounting evidence points toward a predisposing genetic background and dysregulation of both the innate and adaptive immune responses, with follicular or epidermal structures as putative initial targets. To investigate the genetic factors associated with PG susceptibility and severity (arbitrarily defined as unilesional or multilesional), whole-exome sequencing was performed on 11 unrelated patients with PG. Eight carried at least 1 variant of the keratin-encoding genes, including keratin (K)18 gene K18, K20, K23, K32, and K33B. Strikingly, a recurrent variant (rs77999286) of the K18 gene was identified in 5 of 6 patients with multilesional PG and 1 of 5 of those with unilesional PG. AlphaFold modeling and mutation analysis revealed the destabilizing effect of the K18 rs77999286 variant on protein structure. Furthermore, immunohistochemistry revealed undetectable K18 staining in lesional skin compared with that in healthy control skin. Overall, these findings suggest that keratin variants may play a role in PG pathogenesis and indicate that the K18 rs77999286 variant is a potential genetic factor linked to multilesional disease.

Insights into the Pathogenesis of Pyoderma Gangrenosum

Pyoderma gangrenosum (PG) is a neutrophilic dermatosis of unclear etiology. Numerous theories of its underlying pathogenesis have been proposed, including external triggers, neutrophilic dysfunction, complement activation, and autoimmunity, as well as a possible component of underlying genetic susceptibility. This review seeks to synthesize current understanding of the pathogenesis of PG and integrate interactions between the multitude of implicated host immune pathways to guide and inform future directions into the treatment of PG.

The Clinical and Molecular Response of Pyoderma Gangrenosum to IL-23 Blockade: Result from a Proof-of-Concept Open-Label Clinical Trial

Pyoderma gangrenosum is a severe ulcerative disease with a great need for novel therapies. A major barrier to the development of novel therapies is a lack of understanding of disease pathogenesis. We present the results of a proof-of-concept open-label clinical trial of IL-23p19 antagonism with tildrakizumab in pyoderma gangrenosum. Gene expression analysis identified proinflammatory genes associated with IFN responses and dendritic cell activity, including IFI27, XBP1, SAA1 LGALS3, and signal transducer and activator of transcription 3 significantly downregulated in lesional tissue after 12 weeks of therapy. Immunohistochemistry confirmed reduction in IL-17A- and IL-17F-positive cells as well as reduction in TNF-a-, C5a-, and IL-1B-positive cells in week 12 samples compared with those at baseline. Significant reduction in serum inflammation was observed through serum proteomics, with IL-8, IL-6, and CASP-8 levels reduced comparable with those in healthy controls at week 12. Clinical outcomes demonstrated significant reduction in ulcer size, pain, itch, and QOL outcomes in line with the molecular findings. Differential expression of key inflammatory cytokines such as IL-8, CXCL5, PD-L1, SPP1, and matrix metalloproteinase 1 was observed in tissue and serum when stratified by clinical responders and nonresponders. These data provide insights into the clinical relevance of alterations in molecular markers in pyoderma gangrenosum and the potential for the identification of clinically relevant biomarkers of disease activity.

Tofacitinib therapy for severe pyoderma gangrenosum in a patient with enteropathic arthritis: a case-based review

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis that is associated with systemic inflammatory conditions. Currently, there is no universally accepted standard therapy for PG, but immunosuppressive (IS) treatment seems essential. We report a patient here who was successfully treated with tofacitinib despite being PG-refractory to multiple anti-tumor necrosis factor alpha (anti-TNF) therapies and conventional IS. In addition, we performed a comprehensive review of all cases of PG treated with JAK inhibitors. We identified 27 cases treated with JAK inhibitors. Approximately 80% of the patients achieved complete recovery within a median of 12 weeks, even though 17 patients (63%) had received biologics before JAKinib treatment. Notably, this recovery could appear as early as 2 weeks. JAK inhibitors may prove useful in the future, particularly for treating immunosuppressive and steroid-resistant pyoderma gangrenosum, according to recent case reports.

Th Pathways in Immune-Mediated Skin Disorders: A Guide for Strategic Treatment Decisions

In recent years, there have been significant breakthroughs in the identification of immunological components of skin diseases and in the development of immunomodulatory drugs. Novel therapies create exciting prospects for personalized care. This article provides an overview of the role played by Th1, Th2, Th17, and follicular Th pathways in the most common skin diseases. Additionally, it elucidates the impact of current and upcoming treatments on each of these signaling cascades. Skin diseases predominantly influenced by a single dominant Th pathway such as psoriasis and atopic dermatitis are well-suited for biologics. However, in many other disorders a complex interplay between different immune pathways exists. This can lead to inconsistent efficacy of biologics based on individual patient profiles. In case of activation of several Th pathways, it may be more suitable to consider conventional therapies or JAK inhibitors. Increasing immunological insights have transitioned from laboratory research to practical applications, a trend that is expected to continue growing in the future.

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.

Human Inborn Errors of Immunity in Pyoderma Gangrenosum: A Systematic Review

BACKGROUND AND OBJECTIVE

Pyoderma gangrenosum (PG) is a rare ulcerative neutrophilic dermatosis that can be associated with primary immunodeficiency. The pathogenesis of PG has not yet been elucidated, although contributions from dysregulation of the immune system in patients with apparent genetic predispositions have been postulated. We conducted a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-guided systematic review with the objective of identifying inborn errors of immunity in the presence of PG as well as their clinical characteristics of severity including number of PG lesions and anatomic areas affected, and treatment outcomes.

METHODS

A literature search was performed using PubMed/MEDLINE, Embase, Cochrane Library, and Web of Science through August 24, 2023, for studies published in English using the search terms: "pyoderma gangrenosum," "inborn error of immunity," "immune defect*," and a list of genetic mutations potentially associated with PG.

RESULTS

Seventy-four cases of PG associated with inborn errors of immunity were identified. The results demonstrate an association of PG with a variety of inborn errors of immunity, including genetic mutations not classically associated with the condition. Genetic mutations such as BTK, IL1RN, ITGB2, LPIN2, MEFV, NFkB1, NLRP3, NLRP12, NOD2, PSMB8, PLCG2, PSTPIP1, RAG1, TTC37, and WDR1, as well as complement component 2/complement component 4 (C2/C4) and complement component 7 (C7) deficiencies were identified in the presence of either idiopathic or syndromic PG. Of note, mutations in genes such as PSMB8, NLRP3, and IL1RN were found to be associated with a more severe and atypical course of PG, whereas mutations in RAG1 as well as those causing a C2/C4 deficiency were associated with the mildest clinical presentations of PG. Mutations in NFkB1, ITGB2, and PSTPIP1 were associated with the most heterogeneous clinical presentations.

CONCLUSIONS

Human inborn errors of immunity may be implicated in the genetic predisposition to PG and may influence the clinical presentation. Due to the rarity of these diseases, further work must be done to describe the association between inborn errors of immunity and PG. Identifying inborn errors of immunity that may contribute to the development of PG may assist in further elucidating the mechanism of PG, guiding targeted treatment, and improving clinical outcomes for these patients.

IL-12/IL23 blockade reveals patterns of asynchronous inflammation in pyoderma gangrenosum

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis causing chronic and recalcitrant painful ulcerations. Pathogenic mechanisms are yet poorly understood limiting therapeutic options, however, IL-12/IL-23 inhibition via ustekinumab has previously been associated with positive outcomes. We aimed to elucidate the dysregulated immune landscape of PG and lesional skin changes associated with IL-12/IL-23 blockade. We applied spatial transcriptomics and comparative computation analysis on lesional biopsies from two patients obtained before and after IL-12/IL-23 blockade with ustekinumab. Our data indicate lesional PG skin exhibits complex patterns of inflammation, including a not previously described major infiltration of B cells and establishment of tertiary lymphoid structures. In both patients, IL-12/IL-23 blockade led to marked clinical improvement but was associated with amelioration of contrasting inflammatory pathways. Notably, plasma cell markers and tertiary structures were recalcitrant to the treatment regime suggesting that B cells might play a role in the refractory nature of PG.

Treatment of Pyoderma Gangrenosum

Pyoderma gangrenosum is a rare neutrophilic dermatosis that results in painful cutaneous ulcers and is frequently associated with underlying hematologic disorders, inflammatory bowel disease, or other autoimmune disorders. Pathogenesis involves an imbalance between proinflammatory and anti-inflammatory mediators, leading to tissue damage from neutrophils. First-line treatment options with the greatest evidence include systemic corticosteroids, cyclosporine, and tumor necrosis factor alpha inhibitors. Other steroid-sparing therapies such as dapsone, mycophenolate mofetil, intravenous immunoglobulin, and targeted biologic or small molecule inhibitors also have evidence supporting their use. Wound care and management of underlying associated disorders are critical parts of the treatment regimen.

Pyoderma Gangrenosum: Treatment Options

Pyoderma gangrenosum is a rare neutrophilic dermatosis that leads to exceedingly painful ulcerations of the skin. Although the exact pathogenesis is not yet fully understood, various auto-inflammatory phenomena with increased neutrophil granulocyte activity have been demonstrated. Despite the limited understanding of the pathogenesis, it is no longer a diagnosis of exclusion, as it can now be made on the basis of validated scoring systems. However, therapy remains a major multidisciplinary challenge. Various immunosuppressive and immunomodulatory therapies are available for the treatment of affected patients. In addition, concomitant topical pharmacologic therapy, wound management and pain control should always be addressed. Corticosteroids and/or cyclosporine remain the systemic therapeutics of choice for most patients. However, in recent years, there has been an increasing number of studies on the positive effects of biologic therapies such as inhibitors of tumour necrosis factor-α; interleukin-1, interleukin-17, interleukin-23 or complement factor C5a. Biologics have now become the drug of choice in certain scenarios, particularly in patients with underlying inflammatory comorbidities, and are increasingly used at an early stage in the disease rather than in therapy refractory patients.

A novel murine model of pyoderma gangrenosum reveals that inflammatory skin-gut crosstalk is mediated by IL-1β-primed neutrophils

Pyoderma gangrenosum (PG) is a debilitating skin condition often accompanied by inflammatory bowel disease (IBD). Strikingly, ~40% of patients that present with PG have underlying IBD, suggesting shared but unknown mechanisms of pathogenesis. Impeding the development of effective treatments for PG is the absence of an animal model that exhibits features of both skin and gut manifestations. This study describes the development of the first experimental drug-induced mouse model of PG with concomitant intestinal inflammation. Topical application of pyrimidine synthesis inhibitors on wounded mouse skin generates skin ulcers enriched in neutrophil extracellular traps (NETs) as well as pro-inflammatory cellular and soluble mediators mimicking human PG. The mice also develop spontaneous intestinal inflammation demonstrated by histologic damage. Further investigations revealed increased circulating low density IL-1β primed neutrophils that undergo enhanced NETosis at inflamed tissue sites supported by an increase in circulatory citrullinated histone 3, a marker of aberrant NET formation. Granulocyte depletion dampens the intestinal inflammation in this model, further supporting the notion that granulocytes contribute to the skin-gut crosstalk in PG mice. We anticipate that this novel murine PG model will enable researchers to probe common disease mechanisms and identify more effective targets for treatment for PG patients with IBD.

Different molecular pathways are disrupted in Pyoderma gangrenosum patients and are associated with the severity of the disease

Pyoderma gangrenosum (PG) is a rare inflammatory skin disease classified within the spectrum of neutrophilic dermatoses. The pathophysiology of PG is yet incompletely understood but a prominent role of genetics facilitating immune dysregulation has been proposed. This study investigated the potential contribution of disrupted molecular pathways in determining the susceptibility and clinical severity of PG. Variant Enrichment Analysis, a bioinformatic pipeline applicable for Whole Exome Sequencing data was performed in unrelated PG patients. Eleven patients were enrolled, including 5 with unilesional and 6 with multilesional PG. Fourteen pathways were exclusively enriched in the "multilesional" group, mainly related to immune system (i.e., type I interferon signaling pathway), cell metabolism and structural functions. In the "unilesional" group, nine pathways were found to be exclusively enriched, mostly related to cell signaling and cell metabolism. Genetically altered pathways involved in immune system biology and wound repair appear to be nodal pathogenic drivers in PG pathogenesis.

Helicobacter trogontum Bacteremia and Lower Limb Skin Lesion in a Patient with X-Linked Agammaglobulinemia-A Case Report and Review of the Literature

We describe the first case of infection with Helicobacter trogontum in a patient with X-linked agammaglobulinemia. A 22-year-old male with X-linked agammaglobulinemia presented with fever, malaise and a painful skin lesion on the lower left extremity. Spiral shaped Gram-negative rods were isolated from blood cultures and later identified as Helicobacter trogontum. The patient was treated with various intravenous and oral antibiotic regimens over a period of 10 months, each causing seemingly full clinical and paraclinical remission, yet several episodes of relapse occurred after cessation of antibiotic treatment. The review of the literature showed that only a few cases of infections with enterohepatic helicobacters belonging to the Flexispira rappini taxons have previously been reported. The majority of cases included patients with X-linked agammaglobulinemia and the symptomatology and course of disease were similar to the case described here. Infections with enterohepatic helicobacters, including Helicobacter trogontum, should be considered in patients with X-linked agammaglobulinemia presenting with fever, malaise and skin lesions. Careful cultivation and microbiological investigation are essential to determine the diagnosis and a long treatment period of over 6 months must be expected for successful eradication.

Pyoderma Gangrenosum: An Updated Literature Review on Established and Emerging Pharmacological Treatments

Pyoderma gangrenosum is a rare inflammatory skin disease classified within the group of neutrophilic dermatoses and clinically characterized by painful, rapidly evolving cutaneous ulcers with undermined, irregular, erythematous-violaceous edges. Pyoderma gangrenosum pathogenesis is complex and involves a profound dysregulation of components of both innate and adaptive immunity in genetically predisposed individuals, with the follicular unit increasingly recognized as the putative initial target. T helper 17/T helper 1-skewed inflammation and exaggerated inflammasome activation lead to a dysregulated neutrophil-dominant milieu with high levels of tumor necrosis factor-α, interleukin (IL)-1β, IL-1α, IL-8, IL-12, IL-15, IL-17, IL-23, and IL-36. Low-evidence studies and a lack of validated diagnostic and response criteria have hindered the discovery and validation of new effective treatments for pyoderma gangrenosum. We review established and emerging treatments for pyoderma gangrenosum. A therapeutic algorithm based on available evidence is also provided. For emerging treatments, we review target molecules and their role in the pathogenesis of pyoderma gangrenosum.