A Comprehensive Review of Neutrophilic Diseases

Overview of Neutrophilic Biology, Pathophysiology, and Classification of Neutrophilic Dermatoses

Neutrophilic dermatoses are a group of inflammatory skin conditions characterized by a neutrophilic infiltrate on histopathology with no evidence of infection. These conditions present with a wide range of clinical manifestations, including pustules, bullae, abscesses, papules, nodules, plaques, and ulcers. The classification of neutrophilic dermatoses is based on the localization of neutrophils in the skin. The pathogenic mechanisms of neutrophilic dermatoses involve autoinflammation, neutrophilic dysfunction, clonal somatic mutation and differentiation of the myeloid precursors as encountered in myeloid neoplasm.

Superficial and Bullous Neutrophilic Dermatoses: Sneddon-Wilkinson, IgA Pemphigus, and Bullous Lupus

Sneddon-Wilkinson disease (SWD), IgA pemphigus, and bullous systemic lupus erythematosus (BSLE) are superficial and bullous neutrophilic dermatoses. They are all characterized by sterile neutrophilic infiltrate but differ in the level of skin affected and presence of autoantibodies. Both SWD and IgA pemphigus present with grouped flaccid pustules and have epidermal involvement; it is unclear whether they are distinct or exist on a spectrum of the same disease. IgA pemphigus is distinguished from SWD by positive direct immunofluorescence showing intercellular IgA deposition. BSLE presents with tense bullae, dermal neutrophilic infiltrate, and direct immunofluorescence showing linear IgG deposition along the dermal-epidermal junction.

Hidradenitis Suppurativa-Related Autoinflammatory Syndromes: An Updated Review on the Clinics, Genetics, and Treatment of Pyoderma gangrenosum, Acne and Suppurative Hidradenitis (PASH), Pyogenic Arthritis, Pyoderma gangrenosum, Acne and Suppurative Hidradenitis (PAPASH), Synovitis, Acne, Pustulosis, Hyperostosis and Osteitis (SAPHO), and Rarer Forms

Hidradenitis suppurativa (HS) is an autoinflammatory skin disorder of the terminal hair follicle, which can present in sporadic, familial, or syndromic form. A classification has been proposed for the latter, distinguishing cases associated with a known genetic condition, with follicular keratinization disorders or with autoinflammatory diseases. This review focuses on the clinical and genetic features of those entities (ie, pyoderma gangrenosum [PG], acne and HS; PG, acne, pyogenic arthritis and HS; psoriatic arthritis, PG, acne and HS; synovitis, acne, pustulosis, hyperostosis, osteitis; and so forth) for which the collective term HS-related autoinflammatory syndromes is proposed.

Rare Autoinflammatory Neutrophilic Dermatoses in Pregnancy: Literature Review

Rare cases of autoinflammatory neutrophilic dermatoses (AINDs) have been reported in patients during pregnancy with associated adverse maternal and fetal outcomes. Due to the rarity and heterogeneous morphology of pregnancy-associated AINDs, clinical diagnosis is often overlooked, and treatment options are limited. In this review, we present the epidemiology, clinical characteristics, therapeutic interventions, maternal and fetal outcomes, and discuss the possible pathophysiology of various pregnancy associated AINDs. Risk factors for the onset and exacerbation of AINDs in pregnancy include older maternal age, disease duration, and specific gestational age. The varied disease courses and conflicting clinical outcomes in both mothers and fetuses demonstrate the importance of symptom recognition and the understanding of the role of pregnancy on AINDs.

Clinical, epidemiological, and therapeutic hallmarks of pyoderma gangrenosum: a case series of 35 patients

BACKGROUND

Over the past few decades, advances in medical research and diagnostic tools have shed light on some aspects of pyoderma gangrenosum (PG). Nevertheless, the multifactorial etiology, pathogenesis, and optimal management strategies for PG need to be further investigated. To address these knowledge gaps and contribute to a better understanding of this complex dermatological disorder, we collected epidemiological, clinical, and therapeutic aspects of a case series of PG patients occurring in our department over the past 10 years.

METHODS

We performed a single-centered, retrospective, observational study analyzing all cases with a diagnosis of PG observed at the Dermatology clinic of the Fondazione Policlinico A. Gemelli IRCCS Catholic University from January 1, 2013, to January 1, 2023. For each case, we retrieved demographic data, the presence of other skin and systemic conditions, and the histopathological and clinical characteristics of PG, such as clinical variant, number of lesions, disease localization, previous therapy, response to treatment, and occurrence of relapse.

RESULTS

We included 35 patients, 22 females and 13 males with a mean age of 40.0 years. Twenty patients (57.1%) had multiple localizations of disease, and the most commonly involved site was the lower limbs (85.7%). The lesions were mainly associated with inflammatory bowel diseases (51.4%) and hidradenitis suppurativa (37.1%). Clinical resolution with complete re-epithelialization was achieved in 25 patients (71.4%) with an average time of 20.8 months. On average, patients who underwent therapy with biological drugs had better outcomes.

CONCLUSIONS

PG is a severe, rare, and pleomorphic disease associated with a broad spectrum of conditions. Corticosteroids remain the primary first-line approach for severe forms, but using biological immunosuppressants is promising.

The Pathophysiology and Treatment of Pyoderma Gangrenosum-Current Options and New Perspectives

Pyoderma gangrenosum (PG) is an uncommon inflammatory dermatological disorder characterized by painful ulcers that quickly spread peripherally. The pathophysiology of PG is not fully understood; however, it is most commonly considered a disease in the spectrum of neutrophilic dermatoses. The treatment of PG remains challenging due to the lack of generally accepted therapeutic guidelines. Existing therapeutic methods focus on limiting inflammation through the use of immunosuppressive and immunomodulatory therapies. Recently, several reports have indicated the successful use of biologic drugs and small molecules administered for coexisting diseases, resulting in ulcer healing. In this review, we summarize the discoveries regarding the pathophysiology of PG and present treatment options to raise awareness and improve the management of this rare entity.

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.

Neutrophil extracellular traps and neutrophilic dermatosis: an update review

Neutrophils have both antimicrobial ability and pathogenic effect in the immune system, neutrophil extracellular traps (NETs) formation is one of the representative behaviors of their dual role. NETs formation was triggered by pathogen-related components and pathogen non-related proteins as cytokines to exert its effector functions. Recent studies indicate that the pathogenicity of NETs contributed to several skin diseases such as psoriasis, Stevens-Johnson syndrome, toxic epidermal necrolysis, and neutrophilic dermatosis. Especially in neutrophilic dermatosis, a heterogeneous group of inflammatory skin disorders characterized with sterile neutrophilic infiltrate on dermis, NETs formation was reported as the way of participation of neutrophils in the pathogenesis of these diseases. In this review, we describe the different processes of NETs formation, then summarized the most recent updates about the pathogenesis of neutrophilic dermatosis and the participation of NETs, including pyoderma gangrenosum and PAPA syndrome, Behçet syndrome, hidradenitis suppurativa, Sweet Syndrome, pustular dermatosis and other neutrophilic dermatosis. Furthermore, we discuss the link between NETs formation and the development of neutrophilic dermatosis.

Neutrophilic and eosinophilic dermatoses associated with hematological malignancy

Cutaneous manifestations of hematologic malignancy represent both a clinical challenge for the treating physician and a pathophysiological model for advancing the knowledge on individual neoplasms. Indeed, a growing body of evidence supports the concept of recurrent molecular defects associating with specific clinical features, as best exemplified by VEXAS. Herein neutrophilic and eosinophilic dermatoses of potential interest for both hematologists and dermatologists will be reviewed, including subcorneal pustular dermatosis-type IgA pemphigus, neutrophilic eccrine hidradenitis, Sweet's syndrome as well as myelodysplasia cutis and VEXAS, pyoderma gangrenosum, eosinophilic annular erythema, eosinophilic dermatosis of hematological malignancy, Wells syndrome and cutaneous involvement in hypereosinophilic syndromes. Possible management approaches are discussed for each, emphasizing scenarios that require treatment of the underlying condition to achieve remission at the skin level.

Neutrophil extracellular traps formation in the lesional skin of various types of pyoderma gangrenosum

Pyoderma gangrenosum (PG) is a chronic neutrophilic disorder characterized by recurrent painful ulcers. Aseptic inflammation by neutrophils plays an essential role, and neutrophil extracellular traps (NETs) formation can contribute to the pathogenesis of PG. Seventy-five patients were diagnosed as having PG in our department, among which 58 ulcerative, 4 bullous, 3 pustular and 10 vegetative type. We examined the 20 skin biopsy specimens (11 ulcerative, 3 bullous, 2 pustular and 4 vegetative type), and local NETs formation in various types of PG was compared among each type. The biopsied specimens were double labelled for myeloperoxidase, citrullinated histone H3. Immunofluorescent images indicated that the histopathologic location and depth of NETs formation in PG varied by the clinical subtypes. In ulcerative PG, NETs formation was observed in the upper to deep dermis. In bullous PG, NETs formation was mainly observed in the epidermis. Pustular type showed NETs formation in the epidermis near the pustules, and in vegetative type, showed NETs formation mainly in the upper dermis. These results indicate that NETting neutrophils play an important role in the pathogenesis of various forms of PG, although the location and depth of NETs formation in the skin lesion of PG differ depending on each type. Further studies are necessary to examine what factors identify different clinical features of PG.

ZAKα/P38 kinase signaling pathway regulates hematopoiesis by activating the NLRP1 inflammasome

Chronic inflammatory diseases are associated with hematopoietic lineage bias, including neutrophilia and anemia. We have recently identified that the canonical inflammasome mediates the cleavage of the master erythroid transcription factor GATA1 in hematopoietic stem and progenitor cells (HSPCs). We report here that genetic inhibition of Nlrp1 resulted in reduced number of neutrophils and increased erythrocyte counts in zebrafish larvae. We also found that the NLRP1 inflammasome in human cells was inhibited by LRRFIP1 and FLII, independently of DPP9, and both inhibitors regulated hematopoiesis. Mechanistically, erythroid differentiation resulted in ribosomal stress-induced activation of the ZAKα/P38 kinase axis which, in turn, phosphorylated and promoted the assembly of NLRP1 in both zebrafish and human. Finally, inhibition of Zaka with the FDA/EMA-approved drug Nilotinib alleviated neutrophilia in a zebrafish model of neutrophilic inflammation and promoted erythroid differentiation and GATA1 accumulation in K562 cells. In conclusion, our results reveal that the NLRP1 inflammasome regulates hematopoiesis and pave the way to develop novel therapeutic strategies for the treatment of hematopoietic alterations associated with chronic inflammatory and rare diseases.

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.

The Role of Ultra-High-Frequency Ultrasound in Pyoderma Gangrenosum: New Insights in Pathophysiology and Diagnosis

Pyoderma gangrenosum (PG) is a neutrophilic dermatological disease, whose pathogenesis is still poorly clarified. Because of the lack of validated criteria for diagnosis and response, PG treatment is still challenging and should be differentiated in the inflammatory and non-inflammatory phases. Our study aimed to provide a new semi-quantitative approach for PG diagnosis and monitoring, identifying ultra-high-frequency ultrasound (UHFUS) early biomarkers associated with the transition between the two phases. We enrolled 13 patients affected by painful PG lesions evaluated during the inflammatory phase (T0) and during the non-inflammatory phase (T1): pain was measured by the Visual Analogue Scale (VAS); clinical features were recorded through digital photography; epidermis and dermis ultrasound (US) characteristics were evaluated by UHFUS examination with a 70 MHz probe (Vevo MD® FUJIFILM VisualSonics). In T1 UHFUS examination, the presence of hyperechoic oval structures was lower compared to T0 (p value < 0.05). An hyperechogenic structure within the oval structure, suggestive of a hair tract, was evident in T0 and absent in T1 (p value < 0.05). In T0, blood vessels appear as U-shaped and V-shaped anechoic structures with a predominance of U-shaped vessels (p value < 0.05) compared to the more regular distribution found in T1. Finding early biomarkers of the transition from the inflammatory to the non-inflammatory phase could provide new insight in terms of therapeutic decision making and response monitoring. The differences found by this study suggest a potential use of UHFUS for the development of an objective standardized staging method. Further investigations will be necessary to confirm our preliminary results, thus providing a turning point in PG early detection, differential diagnosis and treatment monitoring.

Inborn Errors of Immunity in Hidradenitis Suppurativa Pathogenesis and Disease Burden

Hidradenitis suppurativa (HS), also known as Verneuil's disease and acne inversa, is a prevalent, debilitating, and understudied inflammatory skin disease. It is marked by repeated bouts of pathological inflammation causing pain, hyperplasia, aberrant healing, and fibrosis. HS is difficult to manage and has many unmet medical needs. There is clinical and pharmacological evidence for extensive etiological heterogeneity with HS, suggesting that this clinical diagnosis is capturing a spectrum of disease entities. Human genetic studies provide robust insight into disease pathogenesis. They also can be used to resolve etiological heterogeneity and to identify drug targets. However, HS has not been extensively investigated with well-powered genetic studies. Here, we review what is known about its genetic architecture. We identify overlap in molecular, cellular, and clinical features between HS and inborn errors of immunity (IEI). This evidence indicates that HS may be an underrecognized component of IEI and suggests that undiagnosed IEI are present in HS cohorts. Inborn errors of immunity represent a salient opportunity for rapidly resolving the immunological landscape of HS pathogenesis, for prioritizing drug repurposing studies, and for improving the clinical management of HS.

The double-edged role of neutrophil heterogeneity in inflammatory diseases and cancers

Neutrophils are important immune cells act as the body's first line of defense against infection and respond to diverse inflammatory cues. Many studies have demonstrated that neutrophils display plasticity in inflammatory diseases and cancers. Clarifying the role of neutrophil heterogeneity in inflammatory diseases and cancers will contribute to the development of novel treatment strategies. In this review, we have presented a review on the development of the understanding on neutrophil heterogeneity from the traditional perspective and a high-resolution viewpoint. A growing body of evidence has confirmed the double-edged role of neutrophils in inflammatory diseases and tumors. This may be due to a lack of precise understanding of the role of specific neutrophil subsets in the disease. Thus, elucidating specific neutrophil subsets involved in diseases would benefit the development of precision medicine. Thusly, we have summarized the relevance and actions of neutrophil heterogeneity in inflammatory diseases and cancers comprehensively. Meanwhile, we also discussed the potential intervention strategy for neutrophils. This review is intended to deepen our understanding of neutrophil heterogeneity in inflammatory diseases and cancers, while hold promise for precise treatment of neutrophil-related diseases.

Neutrophilic dermatosis and hidradenitis suppurativa in patients with Behçet's disease: A neutrophilic disease in the spectrum of autoinflammatory syndromes

BACKGROUND

Association of neutrophilic dermatosis (ND), hidradenitis suppurativa (HS) and Behçet's disease (BD) and shared efficacy of TNFα axis blockade suggests common physiopathology.

OBJECTIVES

To investigate the clinical features and therapeutic response of ND and HS associated with BD.

METHODS

We identified 20 patients with ND or HS associated with BD among 1462 patients with BD.

RESULTS

We analysed 20 (1.4%) patients diagnosed with ND or HS associated with BD: 13 HS, 6 pyoderma gangrenosum (PG), and 1 SAPHO. Our 6 PG cases over 1462 BD patients accounts for 400/100 000 prevalence. Thirteen had bipolar aphthosis, 6 vascular, 5 neurologic, and 4 ocular involvements. All PG occurred on limbs and had typical histology with constant dermal neutrophilic infiltrate. All HS had the classical axillary-mammary phenotype. Sixty-nine percent (69%) of HS were Hurley 1 stage. Treatment consisted mainly in colchicine (n = 20), glucocorticoids (n = 12), and anti-TNFα (n = 9). Interesting results with complete or partial responses were obtained with anti-TNFα (9 cases), ustekinumab (3 cases) and tocilizumab (1 case) to treat refractory ND or HS associated with BD.

CONCLUSION

PG seems overrepresented in patients with BD. Biotherapies such as anti-TNFα, ustekinumab and tocilizumab appear to be promising to treat refractory ND or HS associated with BD.

Urticaria: A Narrative Overview of Differential Diagnosis

Urticaria is an inflammatory skin disorder that may occur in isolation or associated with angioedema and/or anaphylaxis. Clinically, it is characterized by the presence of smooth, erythematous or blanching, itchy swelling, called wheals or hives, which greatly vary in size and shape and last less than 24 h before fading to leave normal skin. Urticaria is the consequence of mast-cell degranulation that can be caused by immunological or non-immunological mechanisms. From a clinical point of view, many skin conditions can mimic urticaria and their recognition is mandatory for a correct management and therapeutic approach. We have reviewed all of the main relevant studies which addressed differential diagnosis of urticarial, published until December 2022. The National Library of Medicine PubMed database was used for the electronic research. The present review offers a clinical narrative overview, based on the available literature, of the principal skin disorders that can be misdiagnosed as urticaria (mainly autoinflammatory or autoimmune disorders, drug-induced reactions, and hyperproliferative diseases). The aim of this review is to provide clinicians a useful tool for correctly suspecting and identifying all of these conditions.

A Case of Neutrophilic Dermatoses-Sweet’s Syndrome Coexisting with SAPHO Syndrome

SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome is a rare disease characterized by osteoarticular and cutaneous manifestations. SAPHO syndrome mostly involves the skin, mainly presented as palmoplantar pustulosis and severe acne. Sweet's syndrome (SS) is a neutrophilic dermatosis of unknown cause, which may be caused by autoinflammation. So far, SAPHO syndrome complicated with SS has been rarely reported worldwide. Here, we present a rare case diagnosed in our hospital with detailed clinical information. This patient presented pain and swelling in her right leg. Later, she developed red papules on her right lower eyelid and a skin biopsy showed diffuse lymphocytic and neutrophilic infiltration in the superficial dermis. She was diagnosed with SAPHO syndrome and SS according to medical history and examination. These two diseases share parts of autoinflammatory signaling pathways and might be different variations of the spectrum of autoinflammatory diseases. Through this case, we aim to provide a new horizon for the regulation of neutrophils in SAPHO syndrome and skin lesions like SS.

Practical aspects of the diagnosis and management of pyoderma gangrenosum

Pyoderma gangrenosum (PG) is a rare autoinflammatory ulcerative neutrophilic skin disease. Its clinical presentation is a rapidly progressing painful skin ulcer with ill-defined borders and surrounding erythema. The pathogenesis of PG is complex and not fully understood. Clinically, patients with PG often have various systemic diseases, the most common being inflammatory bowel disease (IBD) and arthritis. Due to the lack of specific biological markers, diagnosing PG remains difficult, which easily resulting in misdiagnosis. Some validated diagnostic criteria have been applied in clinical practice that facilitate its diagnosis. The treatment of PG currently consists mainly of immunosuppressive and immunomodulatory agents, especially biological agents, which have bright prospects for PG therapy. After the systemic inflammatory response is controlled, the problem of wounds becomes the main contradiction in PG treatment. Surgery is not controversial for PG, increasing evidence shows that with adequate systemic treatment, the benefits of reconstructive surgery for patients are increasing.

Autoinflammation in Syndromic Hidradenitis Suppurativa: The Role of AIM2

BACKGROUND

AIM2 is a key cytoplasmatic pathogen-sensor that detects foreign DNA from viruses and bacteria; it can also recognize damaged or anomalous presence of DNA, promoting inflammasome assembly and activation with the secretion of IL-1β, thus sustaining a chronic inflammatory state, potentially leading to the onset of autoinflammatory skin diseases. Given the implication of the IL-1β pathway in the pathogenesis of syndromic hidradenitis suppurativa (HS), an autoinflammatory immune-mediated skin condition, the potential involvement of AIM2 was investigated.

METHODS

Sequencing of the whole coding region of the AIM2 gene, comprising 5'- and 3' UTR and a region upstream of the first exon of ~800 bp was performed in twelve syndromic HS patients.

RESULTS

Six out of twelve syndromic HS patients carried a heterozygous variant c.-208 A ≥ C (rs41264459), located on the promoter region of the AIM2 gene, with a minor allele frequency of 0.25, which is much higher than that reported in 1000 G and GnomAD (0.075 and 0.094, respectively). The same variant was found at a lower allelic frequency in sporadic HS and isolated pyoderma gangrenosum (PG) (0.125 and 0.065, respectively).

CONCLUSION

Our data suggest that this variant might play a role in susceptibility to develop syndromic forms of HS but not to progress to sporadic HS and PG. Furthermore, epigenetic and/or somatic variations could affect AIM2 expression leading to different, context-dependent responses.

Anti-Inflammatory and Antioxidant Effects of Liposoluble C60 at the Cellular, Molecular, and Whole-Animal Levels

Introduction

Liposoluble carbon-60 (C60) has potential applications in many fields, including cosmetics, medical devices, and medicine, but its specific mechanism of action remains unclear. This study explored whether liposoluble C60 could be delivered to human organs, tissues, and cells through blood, extracellular fluid, and cell culture fluid and whether it exerts anti-inflammatory and antioxidant effects at the molecular, cellular, and whole-animal levels.

Methods

At the cellular level, we mixed C60 dissolved in grape seed oil with cell culture medium containing 10% serum and investigated its effects on tumor necrosis factor-α (TNF-α) release, migration, phagocytosis, respiratory burst, and apoptosis in freshly isolated human neutrophils. At the molecular level, we mixed a trace amount of C60 dissolved in grape seed oil with aqueous and ethanolic solutions and studied its antioxidant effect. At the animal level, we investigated the inhibitory effect of C60 on the serum inflammatory marker C-reactive protein (CRP) in beagle dogs after oral administration of C60 dissolved in grape seed oil.

Results

The results showed that the trace amount of C60 dissolved in grape seed oil significantly inhibited TNF-α release, cell migration, phagocytosis, and respiratory burst in freshly isolated human neutrophils. In addition, the trace amount of C60 dissolved in grape seed oil had a significant scavenging effect on superoxide free radicals and 1,1-diphenyl-2-trinitrophenylhydrazine free radicals. Oral administration of C60 dissolved in grape seed oil markedly reduced the level of the serum inflammatory marker CRP in beagle dogs.

Conclusion

In summary, a trace amount of hydrophobic C60 in hydrophilic media effectively produced anti-inflammatory and antioxidant effects in cells and animals. C60 dissolved in grape seed oil is a novel anti-inflammatory and antioxidant drug candidate.

Dermatological manifestations of hematologic neoplasms. Part II: nonspecific skin lesions/paraneoplastic diseases

Cutaneous manifestations occur in the course of hematologic malignancies and precede, accompany or occur late in relation to the diagnosis. They result from paraneoplastic phenomena, tumor infiltrations, immunosuppression resulting from the hematologic disease itself or its treatment. The dermatologist must be aware of these conditions that may be helpful both in the diagnosis of the underlying disease and in reducing patient morbidity. This review (part II) addresses the paraneoplastic dermatological changes associated with systemic hematologic malignancies.

Erosive Pustular Dermatosis: Delving into Etiopathogenesis and Management

Erosive pustular dermatosis (EPD) is a chronic inflammatory skin disorder that usually affects mature individuals. It predominantly affects the scalp and can lead to scarring alopecia. Risk factors include actinic damage and androgenetic alopecia. A traumatic insult to the skin is considered a vital trigger of the condition. EPD is a diagnosis of exclusion; thus, several neoplastic, infectious, vesiculobullous, and inflammatory conditions should be ruled out. Biopsy and clinicopathologic correlation are required to differentiate between EPD and these entities. A dysregulated, chronic immune response is considered central to the etiopathogenesis of EPD. We performed an evidence-based systematic review of the management options. There were predominantly studies with level IV and V evidence and only two with level III. Despite the responsiveness of EPD to potent topical steroids, such as clobetasol propionate, recurrence occurs after treatment withdrawal. With the available data, tacrolimus 0.1%, curettage-assisted aminolevulinic acid-photodynamic therapy, and systemic retinoids can be considered second-line options for EPD with a role in maintenance regimens. However, controlled data and more powerful studies are needed to make solid recommendations.

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

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

Potential Pathogenetic Role of Antimicrobial Peptides Carried by Extracellular Vesicles in an in vitro Psoriatic Model

Purpose

Extracellular Vesicles (EVs) are a heterogeneous group of cell-derived membranous nanoparticles involved in several physiopathological processes. EVs play a crucial role in the definition of the extracellular microenvironment through the transfer of their cargo. Psoriasis is a prototypical chronic inflammatory disease characterized by several secreted mediators, among which antimicrobial peptides (AMPs) are considered pivotal in the development of the psoriatic inflammatory microenvironment. The role of EVs in the pathogenesis of psoriasis has not been elucidated yet, even if emerging evidence demonstrated that interleukin-17A (IL-17A), the psoriasis-related principal cytokine, modifies EVs release and cargo content. The aim of this work was to analyze whether, besides IL-17A, other psoriasis-related cytokines (ie, IFN-γ, TNF-α, IL-22 and IL-23) could affect EVs release and their AMPs mRNAs cargo as well as to analyze the potential biological effect due to EVs internalization by different acceptor cells.

Methods

Nanoparticle tracking analysis (NTA) was performed on supernatants of HaCaT cells stimulated with IL-17A, IFN-γ, TNF-α, IL-22 or IL-23 to enumerate EVs. Real-Time RT-PCR was used for gene expression analysis in cells and EVs. Confocal microscopy and Flow cytometry were used to, respectively, study Netosis and EVs internalization.

Results

IL-17A and IFN-γ increased EVs release by HaCaT cells. All the tested cytokines modulated AMPs mRNA expression in parental cells and in their respective EVs. S100A12 and hBD2 mRNAs were upregulated following IL-17A and IL-22 treatments. Interestingly, EVs derived from cytokine treated HaCaT cells induced Netosis in freshly isolated neutrophils. Upregulation of S100A12 and hBD2 mRNA was also detectable in acceptor cells incubated with EVs derived from cells treated with psoriasis-related cytokines.

Conclusion

The obtained results highlighted the role of EVs in the composition of psoriasis-associated secretome and microenvironment also suggesting the EV involvement in the spreading of the disease mediators and in the possible associated comorbidities.

Molecular feature of neutrophils in immune microenvironment of muscle atrophy

Homeostasis in skeletal muscle is sustained by the balance of functional and physical interactions between muscle and myofibre microenvironment. Various factors, such as ageing, disuse and denervation, tip the balance and induce skeletal muscle atrophy. Skeletal muscle atrophy, which involves complex physiological and biochemical changes, is accompanied by adverse outcomes and even increased mortality. Multiple studies have investigated the role of neutrophils in atrophied skeletal muscles; however, neutrophil intrusion in muscle is still a polemical knot. As technical obstacles have been overcome, people have gradually discovered new functions of neutrophils. The classical view of neutrophils is no longer applicable to their biological characteristics. To date, no clear association between the hidden injurious effect of neutrophil intrusion and muscle atrophy has been convincingly proven. Throughout this review, we have discussed the neutrophil activities that mediate muscle atrophy for distinct disease occurrences. Hopefully, this review will help both clinicians and researchers of skeletal muscle atrophy with relevant targets to further explore efficient medical interventions and treatments.

Neutrophilic dermatoses

Neutrophilic dermatoses (ND) are a group of inflammatory skin conditions characterized by a neutrophilic infiltrate on histopathology with no evidence of infection. ND are classified based upon the localization of neutrophils within the skin and clinical features. Recent findings suggest that ND are due to two main mechanisms: i) a polyclonal hereditary activation of the innate immune system (polygenic or monogenic); or ii) a clonal somatic activation of myeloid cells such as encountered in myelodysplastic syndrome or VEXAS syndrome. ND belong to internal medicine as a great number of patients with ND suffer from an underlying condition (such as hematological malignancy, inflammatory bowel disease, auto-immune and auto-inflammatory diseases). ND are diagnoses of exclusion and physicians should always consider differential diagnoses, particularly skin infections. Here, we review the pathophysiology and classification of the main ND (i.e., subcorneal pustular dermatosis (Sneddon-Wilkinson Disease) and Intercellular IgA dermatoses, aseptic pustulosis of the folds, Sweet syndrome, neutrophilic eccrine hidradenitis, pyoderma gangrenosum, erythema elevatum diutinum, neutrophilic urticarial dermatosis and neutrophilic panniculitis), their clinical and histopathological features, and we highlight the investigations that are useful to identify ND-associated diseases and to exclude the differential diagnoses.

A Case Report of Necrotizing Neutrophilic Dermatosis: A Sheep in Wolf’s Clothing

Neutrophilic dermatosis (ND) is a category of diseases characterized by trauma-induced, autoinflammatory cutaneous eruption. Comorbid systemic disease is common with a predilection for malignancy, inflammatory bowel disease, and rheumatologic disease. Rarely, it can manifest with aseptic shock, an entity referred to as necrotizing neutrophilic dermatosis (NND). NND may occur in the postoperative setting and is often misdiagnosed as a necrotizing soft tissue infection. Unfortunately, the treatment for a necrotizing soft tissue infection, namely, wide debridement, is often detrimental in the setting of NND. We present the case of a woman with underlying myelodysplastic syndrome who developed episodic postoperative hemodynamic collapse followed by delayed necrotic peristomal ulceration following colonic diversion for complicated diverticulitis. Infectious workup and operative re-exploration were unrevealing. Pathologic assessment of affected skin tissue showed changes consistent with ND, ultimately leading to the diagnosis of NND. Her clinical course dramatically improved with the initiation of immunosuppressive therapy. The mimicry of NND to a potentially lethal necrotizing soft-tissue infection creates a grave diagnostic dilemma in the postoperative period. A general lack of knowledge of NND among non-dermatologic specialists produces an opportunity for misdiagnosis and inappropriate surgical interventions, namely, serial debridement. Several clinical cues may aid in the earlier recognition of NND. The cornerstone of treatment involves systemic corticosteroid therapy with adjunctive therapy for refractory cases. NND must be considered in the differential diagnosis of necrotizing soft tissue infection as early recognition may result in the avoidance of deleterious surgical interventions.

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.

Onset of Pyoderma Gangrenosum in Patients on Biologic Therapies: A Systematic Review

OBJECTIVE

To summarize clinical outcomes of paradoxical pyoderma gangrenosum (PG) onset in patients on biologic therapy.

METHODS

The authors conducted MEDLINE and EMBASE searches using PRISMA guidelines to include 57 patients (23 reports).

RESULTS

Of the included patients, 71.9% (n = 41/57) noted PG onset after initiating rituximab, 21.1% (n = 12/57) noted tumor necrosis factor α (TNF-α) inhibitors, 5.3% (n = 3/57) reported interleukin 17A inhibitors, and 1.8% (n = 1/57) reported cytotoxic T-lymphocyte-associated protein 4 antibodies. The majority of patients (94.3%) discontinued biologic use. The most common medications used to resolve rituximab-associated PG were intravenous immunoglobulins, oral corticosteroids, and antibiotics, with an average resolution time of 3.3 months. Complete resolution of PG in TNF-α-associated cases occurred within an average of 2.2 months after switching to another TNF-α inhibitor (n = 1), an interleukin 12/23 inhibitor (n = 2), or treatment with systemic corticosteroids and cyclosporine (n = 3), systemic corticosteroids alone (n = 1), or cyclosporine alone (n = 1).

CONCLUSIONS

Further investigations are warranted to determine whether PG onset is associated with underlying comorbidities, the use of biologic agents, or a synergistic effect. Nevertheless, PG may develop in patients on rituximab or TNF-α inhibitors, suggesting the need to monitor and treat such adverse effects.

Cranial aseptic osteomyelitis associated with pyoderma gangrenosum

Neutrophilic dermatoses include a heterogeneous group of entities. Uncommonly, they can accumulate aseptic neutrophilic abscesses in other tissues in addition to the skin. A 34-year-old female complained of a headache which was unresponsive to usual drugs. A TAC revealed an osteolytic lesion in the right parietal bone. The biopsy showed osteomyelitis. One year later, pyoderma gangrenosum appeared in the anterior aspect of both legs. The headache and the cutaneous lesions disappeared after treatment with oral prednisone. The bone involvement in the background of neutrophilic dermatoses is exceptional. Usually, it involves children in the context of chronic recurrent multiple osteomyelitis (CRMO). Only two cases have been described in adults. One of them was a 26-year-old woman who had had CRMO since childhood, and the other one in contiguity with the cutaneous lesions of pyoderma gangrenosum.

Immune-Mediated Cutaneous Paraneoplastic Syndromes Associated With Hematologic Malignancies: Skin as a Mirror of Hematologic Neoplasms

Malignant neoplasms may present as paraneoplastic syndromes with mucocutaneous manifestations, which may or may not be chronologically associated. The pathophysiological mechanism is complex and not completely understood; therefore, definitive diagnosis may be achieved with a precise differential diagnosis based on the morphology of skin lesions, clinical picture, and histological pattern. The complexities, and low frequency, make the therapeutic approach quite challenging; consequently, the cornerstone of therapy is the eradication of the underlying neoplasms. Corticosteroids are the therapy of choice for most of these immune-mediated manifestations, but for the most part, the successful resolution requires the eradication of the underlying malignancy.

Pyoderma Gangrenosum and Interleukin Inhibitors: A Semi-Systematic Review

BACKGROUND

Pyoderma gangrenosum (PG) is a rare ulcerating skin disease associated with multiple comorbidities and increased mortality. In recent decades, newer biologics such as interleukin inhibitors have been used to treat PG; however, the literature is scarce, consisting predominantly of case reports and caseseries. The aim of our review was to evaluate the effectiveness and safety of interleukin inhibitors for the treatment of PG in adults.

SUMMARY

A literature search was conducted using search terms related to PG and interleukin inhibitors in databases such as PubMed, Embase, Scopus, Web of Science, and Cochrane Library. The study eligibility criteria included patients diagnosed with PG, over the age of 18, and treated with an interleukin inhibitor. Our study included 60 papers describing 81 patients fulfilling the eligibility criteria. The treatment with interleukin inhibitors resulted in 70% (95% CI 59-80%) response and 57% (95% CI 45-68%) complete response rates, and few (4%) mild adverse events, hence supporting the off-label use for the treatment of recalcitrant PG in adults. The response and complete response rates were 59% (17/29) and 38% (11/29) for anakinra, 64% (7/11) and 55% (6/11) for canakinumab, and 79% (27/34) and 71% (24/34) for ustekinumab, respectively. Limitations include publication bias that might have overestimated the efficacy as successful cases responding to treatment are more likely to be reported than nonresponding cases. Additionally, the heterogeneity of the treatment groups does not allow conclusions of superiority or inferiority of the different interleukin inhibitors to be drawn. Further studies are needed to investigate the efficacy of the different interleukin inhibitors and to investigate the importance of underlying disease for treatment response.

IL-17E, iNOS and Arginase1 as new biomarkers in the identification of neutrophilic dermatoses

Background

Neutrophilic dermatoses (ND) are a heterogeneous group of diseases, but can often have a relatively similar histological appearance.

Aim

To identify a combination of biomarkers allowing a better differentiation of ND types.

Methods

Biopsies were obtained from normal human skin (NS; n = 4), chronic plaque‐type psoriasis (PsO; n = 7), paradoxical psoriasis (PP; n = 8), generalized pustular psoriasis (GPP; n = 9), subcorneal pustular dermatosis of Sneddon–Wilkinson (SPD; n = 3), acute generalized exanthematous pustulosis (AGEP; n = 3), hidradenitis suppurativa (HS; n = 7), Sweet syndrome (SS; n = 8) and pyoderma gangrenosum (PG; n = 8). Samples were analysed by immunofluorescence using three biomarkers, interleukin (IL)‐17E, inducible nitric oxide synthase (iNOS) and arginase1, each one in combination with two cell markers, myeloperoxidase (MPO) and CD68, which allow the identification of neutrophils and macrophages, respectively.

Results

We found that SS is characterized by high expression of IL‐17E and iNOS in the epidermis, while PG exhibits low expression. The density of the neutrophil infiltrate helps to differentiate PP (high‐density infiltrate) from PsO (low‐density infiltrate). High expression of arginase1 in the granular layer of the epidermis is a hallmark of SPD. Finally, mature neutrophils and proinflammatory macrophages are readily detectable in PP, SPD and PG, whereas immature neutrophils and anti‐inflammatory macrophages are more frequent in GPP, AGEP, HS and SS.

Conclusions

The analysis of ND by immunofluorescence using IL‐17E, iNOS and arginase1 in combination with MPO and CD68 allows for characterization of differential expression patterns in the epidermis as well as the determination of the polarization status of the dermal neutrophils and macrophages. The appropriate markers may help in the differentiation of ND in clinical practice.

Sterile neutrophilic dermatitis in a cat associated with a topical plant-derived oil flea preventative

A 4-year-old, female spayed, domestic short hair cat presented with an acute eruption of pustules and bullous plaques after application of a plant-based, essential oil flea preventative. Histopathological evaluation of biopsies revealed severe neutrophilic infiltrate within the dermis and culture was negative. The cat's skin lesions responded rapidly to glucocorticoid monotherapy.

A Systematic Review of Depression and Anxiety in Adults with Pyoderma Gangrenosum

OBJECTIVE

To synthesize the available evidence on the prevalence and odds for anxiety and depression in adults with pyoderma gangrenosum (PG).

DATA SOURCES

Observational studies examining anxiety and depression in adults with PG were systematically searched using the MEDLINE, EMBASE, PsycINFO, and CINAHL databases from the inception of each database to March 11, 2020.

STUDY SELECTION

Two authors independently screened references based on predetermined eligibility criteria.

DATA EXTRACTION

Of the 244 articles identified, three met the eligibility criteria. Relevant data were extracted from included studies, and methodological quality was evaluated independently by two authors using the modified Newcastle-Ottawa Scale.

DATA SYNTHESIS

Three observational studies comprising 183 participants with PG met the inclusion criteria. Estimated rates of depression in adults with PG ranged from 10% to 23%. None of the studies measured rates of anxiety.

CONCLUSIONS

The current systematic review suggests that depression is a common psychological comorbidity in adults with PG. Additional research is required to further assess the psychological comorbidities in this population.

Sweet syndrome associated with secondary nodular syphilis in an immunocompetent patient

Sweet syndrome is an inflammatory disease characterized by fever, neutrophilia, papules and erythematous plaques, and a skin neutrophilic infiltrate. Syphilis has been reported among the infectious causes of Sweet syndrome. Syphilis can present atypical manifestations; a rare presentation is nodular syphilis, characterized by nodules with granulomas and plasma cells at histopathology. This case report presents a 20-year-old woman patient, with plaques and nodules, and systemic symptoms. The histopathological exam revealed both non-tuberculoid granulomas and a dense infiltration of polymorphonuclear neutrophils in the dermis. These findings, plus laboratory abnormalities, characteristic of both conditions, were conclusive for Sweet syndrome and nodular syphilis association.

The Impact of Neutrophil Recruitment to the Skin on the Pathology Induced by Leishmania Infection

Leishmania (L.) are obligate intracellular protozoan parasites that cause the leishmaniases, a spectrum of neglected infectious vector-borne diseases with a broad range of clinical manifestations ranging from local cutaneous, to visceral forms of the diseases. The parasites are deposited in the mammalian skin during the blood meal of an infected female phlebotomine sand fly. The skin is a complex organ acting as the first line of physical and immune defense against pathogens. Insults to skin integrity, such as that occurring during insect feeding, induces the local secretion of pro-inflammatory molecules generating the rapid recruitment of neutrophils. At the site of infection, skin keratinocytes play a first role in host defense contributing to the recruitment of inflammatory cells to the infected dermis, of which neutrophils are the first recruited cells. Although neutrophils efficiently kill various pathogens including Leishmania, several Leishmania species have developed mechanisms to survive in these cells. In addition, through their rapid release of cytokines, neutrophils modulate the skin microenvironment at the site of infection, a process shaping the subsequent development of the adaptive immune response. Neutrophils may also be recruited later on in unhealing forms of cutaneous leishmaniasis and to the spleen and liver in visceral forms of the disease. Here, we will review the mechanisms involved in neutrophil recruitment to the skin following Leishmania infection focusing on the role of keratinocytes in this process. We will also discuss the distinct involvement of neutrophils in the outcome of leishmaniasis.