T helper type 1-related molecules as well as interleukin-15 are hyperexpressed in the skin lesions of patients with pyoderma gangrenosum

Differentiating the Role of Inflammation in Hidradenitis Suppurativa from that in Other Inflammatory Skin Diseases

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease characterized by nodules, abscesses, and sinus tunnels, primarily in intertriginous areas. Symptoms of HS are associated with reduced psychosocial health and physical function. HS shares some pathogenic, cellular, and molecular features with other inflammatory skin diseases, highlighting its heterogeneity and complexity. This heterogeneity in disease presentation may contribute to the diagnosis delay observed with HS. The primary objective of this review is to highlight the initiating events, inflammatory signature, molecular features, and clinical features that differentiate HS from other inflammatory skin diseases to improve outcomes for patients with HS.

Gasdermin D-dependent neutrophil extracellular traps exacerbate cytokine storm contributing to pyoderma gangrenosum pathogenesis

Pyoderma gangrenosum (PG) is characterized by the agonizing necrotizing ulcers with non-infectious neutrophil infiltration. Neutrophil extracellular traps (NETs) represent one of the mechanisms of neutrophils activation, and gasdermin D (GSDMD) plays a regulatory role in NETs. In this study, we discovered that the serum levels of NETs were elevated in PG patients compared to healthy controls. Injection of serum from PG patients into the dorsal skin of wild-type mice led to the formation of localized cutaneous ulcers. Furthermore, subsequent modeling demonstrated a significant increase of NETs and GSDMD in skin lesions and peripheral blood serum of wild-type mice. In GSDMD -/- mice, the severity of skin ulcers after modeling was significantly diminished. Overall, our findings shed light on the role of GSDMD in regulating the production of NETs by neutrophils and the release of inflammatory factors in the pathogenesis of PG and establish an animal model for studying PG.

Intravenous Immunoglobulin Therapy for Pyoderma Gangrenosum: A Multicenter Retrospective Analysis in 81 Patients

BACKGROUND

Pyoderma gangrenosum (PG) is rare neutrophil skin disease causing painful, progressively enlarging ulcers. Among the treatment options, intravenous immunoglobulin (IVIG) is a therapy of first choice for paraneoplastic PG. Otherwise, it is used in therapy-refractory courses.

OBJECTIVE

To assess the efficacy and safety of IVIG therapy in patients with PG.

METHODS

A retrospective chart review for patients in five dermatologic wound centres in Germany was performed.

RESULTS

Overall, 81 patients were included. IVIG was used as adjunct therapy with (methyl-) prednisolone and/or a steroid sparing therapy in 77 (95.1%) cases. Response to treatment (combined complete and partial, defined as tendency to heal and cessation of lesion progression, respectively) was 49.3% 1 month after initiation of IVIG. In total 18.8% had a complete response after 6 months. Statistically significantly higher response rates were observed in patients with diabetes mellitus and thyroid disease [odds ratio (OR) 3.49, confidence interval (CI) 1.13-10.80 and OR 6.64, CI 1.01-43.57, respectively]. Patients with solid malignancy tended to have better response (OR 4.36, CI 0.79-23.91). A higher IVIG dose was also associated with a tendency towards better response rates (OR 2.70, CI 0.84-8.63). In total, 1 (1.2%) severe adverse event (myocardial infarction with consequent death) was observed as well as three moderate adverse events, with two thromboembolic events (2.5%) and one acute kidney injury (1.2%). Other adverse events were mild or unlikely to be associated with IVIG therapy, with 14 events in 10 patients overall (12.3%).

CONCLUSIONS

This multicentre retrospective study shows the important role of adjunctive IVIG therapy in patients with PG with recalcitrant courses. Identifying subgroups with a higher probability of response could improve future response rates and save patients from ineffective treatment and potential adverse events.

Molecular Characteristics of Sweet Syndrome: A Systematic Review

Sweet syndrome (SS), originally described as acute febrile neutrophilic dermatosis, is a rare inflammatory skin condition, considered the prototype of neutrophilic dermatoses. It is characterised by the sudden onset of well-defined tender papules, plaques and nodules often accompanied by fever, neutrophilia and elevated markers of inflammation. Several variants have been described both clinically and histopathologically. Classifications include idiopathic, malignancy-associated, and drug-induced SS. The exact pathogenesis of SS is still unclear; however, recent findings have shed light on the role of dermal infiltrating neutrophils-in the context of innate immunity, and signalling pathways related to adaptive immunity. To critically analyse the current molecular landscape of SS and discuss the recent evidence supporting novel potential immune mediators and biological signalling pathways involved in SS pathogenesis. The methodology followed PRISMA guidelines and included two bibliographical databases, searching articles published until 17 December 2023. Titles, abstracts and full text were reviewed independently by two assessors, while other two investigators resolved any opinion differences. Of 3303 records identified through database search, 22 articles met the eligibility criteria for inclusion. We considered experimental studies that performed molecular analysis, in terms of cytokines quantification, gene expression and/or immunofluorescence/immunohistochemistry. As for the latter, only studies aimed at characterising the nature of the inflammatory infiltrate and potential mechanisms leading to distinct forms of cutaneous inflammatory cell influx were included. Overall, we described research on 202 SS patients (177 skin biopsies and 25 blood specimens) revealing the predominant role of neutrophil activation and abnormal proliferation as unifying mechanisms in different SS subtypes. Interestingly, we found that hyperactivation of the IL-1 pathway might occur only in a subset of SS patients and adaptive immunity could also play a role in the pathogenic scenario of SS, with a potential significant role of IL-17 axis. This systematic review provides a wealth of evidence on the molecular landscape of SS, although further research is needed to a deeper understanding of the patho-mechanisms of this rare disease and hopefully lead to targeted therapeutic approaches.

Pyoderma Gangrenosum Associated With Iatrogenic Interleukin 17A Blockade: A Report of Two Cases and a Review of the Literature

Pyoderma gangrenosum (PG) is a rare necrotizing neutrophilic dermatosis driven by monokines and cytokines elaborated by monocytes and autoreactive T cells, respectively. Th1-mediated autoimmune disorders and myeloproliferative disease are among the potential disease associations. More recently, certain medications were implicated, including TNF-alpha inhibitors, rituximab, and IL-17A inhibitors, such as secukinumab, where the development of PG is held to represent a cutaneous immune adverse effect. We present two patients who developed an autoinflammatory syndrome resembling PG in the setting of drug therapy with agents exhibiting an IL-17A inhibitory effect. The drugs were erunumab in one and secukinumab in the other. One patient received the anti-calcitonin gene-related peptide targeted therapy, erenumab, for migraine prophylaxis. While this drug has not been previously implicated in the development of PG, it can cause IL-17A blockade. The other patient was on secukinumab, a monoclonal antibody that selectively targets IL-17A. We documented a microenvironment enriched in IL-17A, emphasizing that the blockade impacts the functionality of the receptor as opposed to a quantitative reduction in IL-17A production by T cells. Qualitative functional IL-17A blockade could result in a paradoxical increase in IL-23, a pro-inflammatory cytokine that may contribute to the influx of neutrophils pathogenetically implicated in PG.

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.

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.

Genetic mutations in pyoderma gangrenosum, hidradenitis suppurativa, and associated autoinflammatory syndromes: Insights into pathogenic mechanisms and shared pathways

Pyoderma gangrenosum (PG), hidradenitis suppurativa (HS), and the associated autoinflammatory syndromes, including pyogenic arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome, PSTPIP1-associated myeloid-related proteinemia inflammatory (PAMI) syndrome, pyoderma gangrenosum, acne, and hidradenitis suppurativa (PASH) syndrome, and pyogenic arthritis, pyoderma gangrenosum, acne, and suppurative hidradenitis (PAPASH) syndrome are dermatological conditions characterized by chronic inflammation and tissue damage. Recent advances in genetic research have identified specific mutations associated with these disorders, shedding light on their underlying pathogenic mechanisms. This review aims to summarize the current knowledge of identified mutations and presumed pathophysiology in PG, HS, and the associated autoinflammatory syndromes.

New treatment of pyoderma gangrenosum and hidradenitis suppurativa: A review

Pyoderma gangrenosum (PG) and hidradenitis suppurativa (HS) are stubborn inflammatory skin diseases categorized as neutrophilic hypodermal dermatoses. These conditions exhibit connections with other autoinflammatory disorders driven by immune responses. Their pathogenesis is complex, rooted in significant imbalances in both innate and adaptive immune systems, particularly featuring elevated levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1, IL-8, IL-17, and IL-23. Studies involving skin tissue pathology and serology have indicated that targeting specific cytokines can bring therapeutic benefits. Indeed, many patients in clinical settings have responded positively to such interventions. Yet, given the diverse cytokines in play, focusing on a single one with antibody therapy might not always be effective. When resistance to biologics emerges, a combined approach targeting multiple overactive cytokines with immunosuppressants, for example cyclosporine and Janus kinase inhibitors, could be an option. In the current review, we explore recent therapeutic developments for PG and HS.

Cutaneous manifestations of inflammatory bowel disease: basic characteristics, therapy, and potential pathophysiological associations

Inflammatory bowel disease (IBD) is a chronic inflammatory disease typically involving the gastrointestinal tract but not limited to it. IBD can be subdivided into Crohn's disease (CD) and ulcerative colitis (UC). Extraintestinal manifestations (EIMs) are observed in up to 47% of patients with IBD, with the most frequent reports of cutaneous manifestations. Among these, pyoderma gangrenosum (PG) and erythema nodosum (EN) are the two most common skin manifestations in IBD, and both are immune-related inflammatory skin diseases. The presence of cutaneous EIMs may either be concordant with intestinal disease activity or have an independent course. Despite some progress in research on EIMs, for instance, ectopic expression of gut-specific mucosal address cell adhesion molecule-1 (MAdCAM-1) and chemokine CCL25 on the vascular endothelium of the portal tract have been demonstrated in IBD-related primary sclerosing cholangitis (PSC), little is understood about the potential pathophysiological associations between IBD and cutaneous EIMs. Whether cutaneous EIMs are inflammatory events with a commonly shared genetic background or environmental risk factors with IBD but independent of IBD or are the result of an extraintestinal extension of intestinal inflammation, remains unclear. The review aims to provide an overview of the two most representative cutaneous manifestations of IBD, describe IBD's epidemiology, clinical characteristics, and histology, and discuss the immunopathophysiology and existing treatment strategies with biologic agents, with a focus on the potential pathophysiological associations between IBD and cutaneous EIMs.

Clinical guidance of pyoderma gangrenosum 2022

Pyoderma gangrenosum (PG) is a rare, neutrophilic skin disease. For the purpose of accurate diagnosis and proper treatment of PG, the Japanese clinical practice guidance for PG developed by the Japanese Dermatological Association was published in 2022. In this guidance, clinical aspects, pathogenesis, current therapies, and clinical questions on PG are described from the viewpoints of current knowledge and evidence-based medicine. Here, the English version of the Japanese clinical practice guidelines for PG is presented and is intended to be widely referred to in the clinical examination and treatment of PG.

An unusual presentation of celiac disease in adult patient

Pyoderma gangrenosum is among the exceptional extra-intestinal manifestations of celiac disease. We report a case of a 52-year-old patient who presented with pyoderma gangrenosum that turned out to be the initial presentation of celiac disease.

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.

Epidermotropie von Immunzellen unterscheidet Pyoderma gangraenosum vom Ulcus cruris venosum

HINTERGRUND UND ZIELE

Pyoderma gangraenosum ist eine ulzerierende, autoinflammatorische Erkrankung. Es gibt keine eindeutigen histopathologischen Merkmale zur Differenzierung von anderen Ursachen chronischer Wunden wie dem Ulcus cruris venosum. Ziel dieser Studie war es, histopathologische Merkmale von Pyoderma gangraenosum und Unterschiede zu venösen Ulzerationen zu detektieren.

PATIENTEN UND METHODIK

Acht Gewebeproben von Pyoderma gangraenosum, zwölf Proben von Ulcus cruris venosum und sechs Proben von gesunder Haut wurden einer immunhistologischen Multi-Antigen-Analyse unterzogen. Das Immuninfiltrat und seine räumliche Verteilung wurden anhand von Fluoreszenzbildern mit einer Gewebezytometriesoftware analysiert.

ERGEBNISSE

Die dichte epidermale Präsenz von CD45RO⁺ -T-Gedächtnis-Zellen und die Rarefizierung von CD1a⁺ -Langerhans-Zellen in der Epidermis waren Marker für Pyoderma gangraenosum, welche auch auf eine epidermale Immunreaktion schließen lassen. Darüber hinaus konnte dermal eine hohe Anzahl CD11c⁺ CD68⁺ pro-inflammatorischer M1-Makrophagen nachgewiesen werden. Diese überstieg die Anzahl der in venösen Ulzerationen beobachteten Makrophagen deutlich.

SCHLUSSFOLGERUNGEN

Die histopathologischen Unterschiede zwischen Pyoderma gangraenosum und Ulcus cruris venosum können zur Unterscheidung der beiden Erkrankungen herangezogen werden und somit eine wichtige Hilfe zur schnellen Einleitung einer adäquaten Therapie sein. Darüber hinaus deuten unsere Daten auf einen antigengesteuerten Prozess in der Epidermis hin, möglicherweise unter Beteiligung von CD1a⁺ Langerhans-Zellen.

Skin Manifestation Induced by Immune Checkpoint Inhibitors

In accordance with recent therapeutic progress of immune checkpoint inhibitors for certain cancers, various disorders are induced as immune-related adverse events (irAEs) affecting the skin, gut, thyroid gland, lung, and liver. Among such irAEs, mucocutaneous manifestation is the most common. Cutaneous manifestations are categorized into several groups, ie, inflammatory reactions, immunobullous reactions, alterations of epidermal keratinocytes, and alterations of epidermal melanocytes; however, there are additionally various cutaneous toxicities, unclassified into those groups. Blocking of programmed cell death 1 (PD-1)/programmed cell death ligand 1(PDL1) can lead to the induction of autoimmune reaction, via activation of cytotoxic T cells, inhibition of regulatory T cell function, and alteration of cytokine balance. Similarly, blockade of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) reduces the suppressive function of regulatory T cells. Due to those mechanisms, various autoimmune conditions can be induced, in addition to nonspecific drug eruptions. Dermatologists should be aware of various types of those mucocutaneous manifestations, either common or rare, as well as the management of such conditions. Herein, various mucocutaneous manifestations of irAEs and cases involving Japanese patients have been described, based on a single institute's experience.

Epidermotropism of inflammatory cells differentiates pyoderma gangrenosum from venous leg ulcers

BACKGROUND AND OBJECTIVES

Pyoderma gangrenosum is an ulcerative autoinflammatory disease, lacking distinct histopathological characteristics to differentiate from other ulcerating conditions, like venous leg ulcers. The objective of this study was therefore to find histopathological characteristics of pyoderma gangrenosum in a head-to-head comparison to venous leg ulcers.

PATIENTS AND METHODS

Eight tissue samples of pyoderma gangrenosum, twelve samples of venous leg ulcers and six samples of healthy skin were stained using an immunohistological multi antigen staining technology. The immune infiltrate and its spatial distribution were analyzed with contextual tissue cytometry software using fluorescence images.

RESULTS

The dense epidermal presence of CD45RO⁺ memory T cells and the rarefication of CD1a⁺ Langerhans cells in the epidermis were defining markers for pyoderma gangrenosum, implicating an epidermal immune reaction. In addition, high numbers of CD11c⁺ CD68⁺ pro-inflammatory M1 macrophages were detected in the dermis, significantly extending the numbers seen in venous leg ulcers.

CONCLUSIONS

The histopathological differences found between pyoderma gangrenosum and venous leg ulcer can be used to distinguish between the two diseases and thus provide an important aid for the rapid initiation of adequate therapy. In addition, our data hint at an antigen-driven process in the epidermis, possibly involving CD1a⁺ Langerhans cells.

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

Pyoderma Gangrenosum is a painful recurrent ulcerative neutrophilic dermatosis in which the pathogenesis is incompletely defined. Current evidence suggests that PG is associated with dysregulation of components of both the innate and adaptive immune system with dysregulation of neutrophil function and contribution of the Th17 immune axis. PG can present in numerous heterogeneous clinical presentations and be associated with multiple inflammatory conditions including Rheumatoid Arthritis, inflammatory bowel disease and hidradenitis suppurativa. However, no critical evaluation of the observed molecular characteristics in PG studies in association with their clinical findings has been assessed. Additionally, emerging evidence suggests a potential role for other cell types and immune pathways including B cells, macrophages, autoantibodies, and the complement system in PG although these have not yet been integrated into the pathogenesis of disease. This systematic review aims to critically evaluate the current molecular observations regarding the pathogenesis of PG and discuss associations with clinical characteristics as well as the evidence supporting novel cell types and immune pathways in PG.

Adult-onset immunodeficiency due to anti-interferon-gamma autoantibody-associated Sweet syndrome: A distinctive entity

Sweet syndrome (SS) has been increasingly reported in patients with adult-onset immunodeficiency (AOID) due to anti-interferon-γ autoantibody who also have concomitant opportunistic infections, especially disseminated non-tuberculous mycobacterial infection (dNTMI). A retrospective study retrieving data from 2011 through 2020 was conducted. We compared clinical characteristics of SS with and without AOID and generated the prediction model and examined the interaction between AOID and dNTMI in the occurrence of SS. Lymphadenopathy, pustular lesions, and leukocytosis are the significant predictors for AOID-associated SS. Adjusted risk differences were 0.58 (95% confidence interval [CI], 0.33-0.83), 0.21 (95% CI, 0.02-0.39), and 0.24 (95% CI, 0.01-0.47), respectively. Based on the analysis of aggregated cross-sectional data, both the overall and the direct effect of AOID increased the prevalence of SS. The indirect effect of AOID on the occurrence of SS might also be mediated through dNTMI or other common opportunistic infections. In addition, there was a trend of positive additive interaction between AOID and dNTMI. Although the test of additive interaction did not reveal statistically significant results, a deviation from additivity of isolated effects might suggest potential causal interaction between AOID and dNTMI. The distinctive clinical syndrome comprising lymphadenopathy, pustular lesions, and leukocytosis in patients with SS should raise the awareness of clinicians to the potential of underlying AOID.

Sweet Syndrome Following SARS-CoV2 Vaccination

Vaccines are today considered one of the most effective means against the Sars-CoV-2 pandemic. The BNT162b2 vaccine by Pfizer/BioNTech has been massively administered throughout the globe; since its approval, a wide spectrum of cutaneous reactions has been reported. Here we report the case of a 52-year-old Caucasian male who presented with an acute febrile eruption that arose 72 h after the first dose of the BNT162b2 vaccine. The clinicopathological findings were consistent with Sweet's syndrome. The short latency time suggested a possible role of the vaccine in triggering Sweet's syndrome in this case.

Propranolol Off-Target: A New Therapeutic Option in Neutrophil-Dependent Dermatoses?

Epidermolysis bullosa acquisita (EBA) is a rare subepidermal blistering dermatosis characterized by autoantibodies targeting collagen VII (COL7), an essential component of the anchoring fibrils, located in the sublamina densa of the dermal‒epidermal junction. In EBA, tissue-bound autoantibodies cause the recruitment and subsequent activation of neutrophils, which eventually lead to subepidermal blistering through the release of proteases and ROS. Thus, targeting either pathogenic IgG autoantibodies or neutrophil recruitment or activation has shown efficacy in experimental murine EBA models and patients with EBA. In this issue, Stüssel et al. demonstrate that propranolol, a nonselective β-adrenoreceptor blocker, markedly inhibits the neutrophil release of ROS induced by complexes of COL7 and/or anti-COL7 IgG in vitro and ameliorates the formation of blisters and erosions in an antibody passive-transfer model of murine EBA. These findings warrant further investigations aimed at characterizing the therapeutic efficacy of propranolol in EBA and possibly beyond.

Dermatological Manifestations in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBDs) may be associated with extra-intestinal manifestations. Among these, mucocutaneous manifestations are relatively frequent, often difficult to diagnose and treat, and may complicate the course of the underlying disease. In the present review, a summary of the most relevant literature on the dermatologic manifestations occurring in patients with inflammatory bowel diseases has been reviewed. The following dermatological manifestations associated with IBDs have been identified: (i) specific manifestations with the same histological features of the underlying IBD (occurring only in Crohn's disease); (ii) cutaneous disorders associated with IBDs (such as aphthous stomatitis, erythema nodosum, psoriasis, epidermolysis bullosa acquisita); (iii) reactive mucocutaneous manifestations of IBDs (such as pyoderma gangrenosum, Sweet's syndrome, bowel-associated dermatosis-arthritis syndrome, aseptic abscess ulcers, pyodermatitis-pyostomatitis vegetans, etc.); (iv) mucocutaneous conditions secondary to treatment (including injection site reactions, infusion reactions, paradoxical reactions, eczematous and psoriasis-like reactions, cutaneous infections, and cutaneous malignancies); (v) manifestations due to nutritional malabsorption (such as stomatitis, glossitis, angular cheilitis, pellagra, scurvy, purpura, acrodermatitis enteropathica, phrynoderma, seborrheic-type dermatitis, hair and nail abnormalities). An accurate dermatological examination is essential in all IBD patients, especially in candidates to biologic therapies, in whom drug-induced cutaneous reactions may assume marked clinical relevance.

Immune-Mediated Dermatoses in Patients with Haematological Malignancies: A Comprehensive Review

Haematological malignancies induce important alterations of the immune system, which account for the high frequency of autoimmune complications observed in patients. Cutaneous immune-mediated diseases associated with haematological malignancies encompass a heterogeneous group of dermatoses, including, among others, neutrophilic and eosinophilic dermatoses, autoantibody-mediated skin diseases, vasculitis and granulomatous dermatoses. Some of these diseases, such as paraneoplastic pemphigus, are associated with an increased risk of death; others, such as eosinophilic dermatoses of haematological malignancies, run a benign clinical course but portend a significant negative impairment on a patient’s quality of life. In rare cases, the skin eruption reflects immunological alterations associated with an unfavourable prognosis of the associated haematological disorder. Therapeutic management of immune-mediated skin diseases in patients with haematological malignancies is often challenging. Systemic corticosteroids and immunosuppressive drugs are considered frontline therapies but may considerably augment the risk of serious infections. Indeed, developing a specific targeted therapeutic approach is of crucial importance for this particularly fragile patient population. This review provides an up-to-date overview on the immune-mediated skin diseases most frequently encountered by patients with onco-haematological disorders, discussing new pathogenic advances and therapeutic options on the horizon.

Pyoderma gangrenosum

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis that presents with rapidly developing, painful skin ulcers hallmarked by undermined borders and peripheral erythema. Epidemiological studies indicate that the average age of PG onset is in the mid-40s, with an incidence of a few cases per million person-years. PG is often associated with a variety of other immune-mediated diseases, most commonly inflammatory bowel disease and rheumatoid arthritis. The cause of PG is not well understood, but PG is generally considered an autoinflammatory disorder. Studies have focused on the role of T cells, especially at the wound margin; these cells may support the destructive autoinflammatory response by the innate immune system. PG is difficult to diagnose as several differential diagnoses are possible; in addition to clinical examination, laboratory tests of biopsied wound tissue are required for an accurate diagnosis, and new validated diagnostic criteria will facilitate the process. Treatment of PG typically starts with fast-acting immunosuppressive drugs (corticosteroids and/or cyclosporine) to reduce inflammation followed by the addition of more slowly acting immunosuppressive drugs with superior adverse event profiles, including biologics (in particular, anti-tumour necrosis factor (TNF) agents). Appropriate wound care is also essential. Future research should focus on PG-specific outcome measures and PG quality-of-life studies.

Pyoderma gangrenosum: proposed pathogenesis and current use of biologics with an emphasis on complement C5a inhibitor IFX-1

INTRODUCTION

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis with no FDA-approved treatment. The complement pathway has received renewed attention because it is elevated in inflammatory cutaneous conditions such as hidradenitis suppurativa (HS) and psoriasis. IFX-1 is a complement C5a inhibitor which inhibits neutrophil activation, chemotaxis, and reduces inflammatory signaling and complement driven tissue damage in various diseases.

AREAS COVERED

The article discusses a proposed pathogenesis of PG, early clinical investigations of IFX-1 for the treatment of HS and PG, its potential as a treatment for PG, and those other biologics currently under investigation.

EXPERT OPINION

Further studies should explore how patients with PG and other neutrophilic conditions may respond to complement inhibitors such as IFX-1. C5a blockade led to a reduction in inflammatory tunnels in HS, and alteration in neutrophil migration and activation supports the role of this pathway in the development of PG. The main challenges to the approval of IFX-1 are the identification of the optimal dose, duration, and stage-dependent factors in cutaneous inflammatory disorders. Further studies are required; however, complement inhibitors such as IFX-1 could find a place in clinical practice in years to come for severe, resistant PG that does not respond to conventional therapies.

Paraneoplastic Dermatoses: A Brief General Review and an Extensive Analysis of Paraneoplastic Pemphigus and Paraneoplastic Dermatomyositis

Skin manifestations of systemic disease and malignancy are extremely polymorphous. Clinicians should be familiarized with paraneoplastic dermatoses in order to perform an early diagnosis of the underlying neoplasm. Lack of familiarity with cutaneous clues of internal malignancy may delay diagnosis and treatment of cancer. In this review, we described several paraneoplastic dermatoses and discussed extensively two paradigmatic ones, namely paraneoplastic pemphigus and paraneoplastic dermatomyositis.

NK Cell and Fibroblast-Mediated Regulation of Skin Squamous Cell Carcinoma Invasion by CLEC2A Is Compromised in Xeroderma Pigmentosum

The ability of cancer cells to invade and disseminate can be affected by components of the surrounding microenvironment. To identify dermal components that regulate the growth of epidermal carcinomas, we studied the genetic disease called xeroderma pigmentosum that bears mutations in genes involved in the nucleotide excision repair of DNA. Patients with xeroderma pigmentosum are more prone to develop cutaneous tumors than the general population and their dermal fibroblasts display the features of dermal cancer-associated fibroblasts, which promote the invasion of keratinocytes. Here, we report that 3-dimensional dermal cultures of fibroblasts from healthy donors but not from patients with xeroderma pigmentosum complementation group C express CLEC2A, which is the ligand of the activating NK cell receptor NKp65. A similar loss of CLEC2A was observed in sporadic dermal cancer-associated fibroblasts and upon the culture of fibroblasts with cutaneous squamous cell carcinoma-conditioned medium. Using an innovative 3-dimensional organotypic skin culture model that contain NK cells in addition to fibroblasts and squamous cell carcinoma cells, we unveiled a key role of CLEC2A that orchestrates a crosstalk between fibroblasts and NK cells, thereby leading to the control of squamous cell carcinoma invasion. These findings indicate that CLEC2A-expressing dermal fibroblasts play a major role in immune surveillance of the skin.

Insights Into the Pathogenesis of Sweet's Syndrome

Sweet's syndrome, also known as Acute Febrile Neutrophilic Dermatosis, is a rare inflammatory condition. It is considered to be the prototype disease of neutrophilic dermatoses, and presents with acute onset dermal neutrophilic lesions, leukocytosis, and pyrexia. Several variants have been described both clinically and histopathologically. Classifications include classic Sweet's syndrome, malignancy associated, and drug induced. The cellular and molecular mechanisms involved in Sweet's syndrome have been difficult to elucidate due to the large variety of conditions leading to a common clinical presentation. The exact pathogenesis of Sweet's syndrome is unclear; however, new discoveries have shed light on the role of inflammatory signaling, disease induction, and relationship with malignancy. These findings include an improved understanding of inflammasome activation, malignant transformation into dermal infiltrating neutrophils, and genetic contributions. Continued investigations into effective treatments and targeted therapy will benefit patients and improve our molecular understanding of inflammatory diseases, including Sweet's syndrome.

Classic Ulcerative Pyoderma Gangrenosum Is a T Cell-Mediated Disease Targeting Follicular Adnexal Structures: A Hypothesis Based on Molecular and Clinicopathologic Studies

Background

Pyoderma gangrenosum (PG) is a debilitating ulcerative skin disease that is one of the most common associated diseases seen in patients with inflammatory bowel disease and rheumatoid arthritis. Although PG is classified as a neutrophilic dermatosis, its pathophysiology is poorly understood.

Objective

Use data obtained from patient-reported histories, immunohistochemistry, and gene expression analysis to formulate a hypothesis on PG pathophysiology.

Methods

Ten PG patients participated and answered questions about new ulcer formation. Skin biopsies of healed prior ulcers and adjacent normal skin were obtained from four patients for immunohistochemistry. Scars from healthy patients and patients with discoid lupus were used as additional controls. New onset PG papules were analyzed using immunohistochemistry and gene expression analysis via quantitative real-time PCR.

Results

All PG patients reported that healed sites of previous ulceration are refractory to re-ulceration. Simultaneous biopsies of healed and uninvolved skin triggered ulceration only in the latter. On immunohistochemistry, healed PG scars showed complete loss of pilosebaceous units, which were present in normal skin, and to a lesser extent in control scars, and discoid scars. Early PG papules showed perivascular and peripilosebaceous T cell infiltrates, rather than neutrophils. These early inflammatory events were dominated by increased gene expression of CXCL9, CXCL10, CXCL11, IL-8, IL-17, IFNG, and IL-36G and transcription factors consistent with Th1 phenotype.

Limitations

Small sample size was the main limitation.

Conclusion

We put forth the hypothesis that PG is a T cell response resulting in the destruction of pilosebaceous units.