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.

The Neutrophilic Dermatoses, or the Cutaneous Expressions of Neutrophilic Inflammation

Acute febrile neutrophilic dermatosis, or Sweet syndrome, has been described in 1964 and is now considered as a prototypical condition of the group of the neutrophilic dermatoses. Since this time, many clinical conditions have been included in this group and a clinical-pathological classification in 3 subgroups has been proposed. Neutrophilic infiltrates can localize in all internal organs. This defines the neutrophilic disease, which induces difficult diagnostic and therapeutic problems. Autoinflammation is the main pathophysiological mechanism of the neutrophilic dermatoses. There is a special link between myeloid malignancies (leukemia and myelodysplasia) and the neutrophilic dermatoses.

Characterization and Management of Amicrobial Pustulosis of the Folds, Aseptic Abscess Syndrome, Behçet Disease, Neutrophilic Eccrine Hidradenitis, and Pyostomatitis Vegetans-Pyodermatitis Vegetans

Neutrophilic dermatoses are a broadly heterogeneous group of inflammatory skin disorders. This article reviews 5 conditions: amicrobial pustulosis of the folds, aseptic abscess syndrome, Behçet disease, neutrophilic eccrine hidradenitis, and pyostomatitis vegetans-pyodermatitis vegetans.The authors include up-to-date information about their epidemiology, pathogenesis, clinicopathologic features, diagnosis, and management.

Role of neutrophils in cutaneous lupus erythematosus

There are various types of cutaneous lupus erythematosus (CLE), either with or without the association of systemic lupus erythematosus (SLE). In some of the subtypes of cutaneous lupus, histopathology reveals neutrophil infiltration in the lesional skin; however, the significance of neutrophils in CLE is not yet fully elucidated. Recent studies have shown that neutrophil extracellular traps (NETs) formation by activated neutrophils is observed in several types of CLE, including lupus panniculitis, subacute lupus erythematosus, and acute lupus erythematosus, although the number of reports is small. Excessive NETosis, due to either increased NETs formation or defective clearance of NETs, may play a role in the induction of autoimmunity and autoantibody production in SLE, as well as endothelial damage, thrombus formation, and vascular damage in the lesional skin. CLE is an excessive interferon-driven autoimmune disease. Plasmacytoid dendritic cells are located in lupus erythematosus skin and contribute to the etiology of skin lesions as a main producing cell of type I interferon. Neutrophils, monocytes, and keratinocytes also produce type I interferon via several triggers. Neutrophils play an important role in the innate immune response in SLE. In this review, several types of CLE with neutrophil infiltration, as well as the role of neutrophils are discussed.

Amicrobial pustulosis of the folds: A case report of a rare variant of neutrophilic dermatosis associated with systemic lupus erythematosus

Amicrobial pustulosis of the folds (APF) is a rare neutrophilic dermatosis found in association with autoimmune diseases. We present a 49-year-old woman with a history of systemic lupus erythematosus and a recurrent pustular eruption in the cutaneous folds. Histologic examination revealed spongiform pustulosis and dermal neutrophilic infiltrate. The Gram and periodic acid-Schiff stains were negative for bacteria and fungi. A diagnosis of amicrobial pustulosis of the folds was given. While there is no standard treatment, our patient's symptoms resolved following an oral prednisone taper and have not recurred since starting colchicine. The presence of pustules and erosive plaques in skin folds in young women with autoimmune conditions should raise suspicion for APF. The combination of localized neutrophilic spongiosis with intraepidermal or subcorneal pustules in conjunction with dermal changes of a neutrophilic dermatosis is a helpful clue to the diagnosis. If the patient does not already have a diagnosis of an underlying autoimmune condition, a presentation of APF should prompt further screening consisting of a relevant review of symptoms and appropriate assessment for autoimmune antibodies, since APF may precede the diagnosis of autoimmune disorders.

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.

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.

Pustular lesions in patients with Crohn disease and treatment with tumour necrosis factor-α inhibitors

We present seven new cases of patients with Crohn disease who developed lesions clinically compatible with amicrobial pustulosis of the flexures during their treatment with anti-tumour necrosis factor therapy.

Neutrophilic dermatoses with unusual and atypical presentations

Neutrophilic dermatoses (NDs) are a group of reactive, noninfectious autoinflammatory diseases characterized by (1) infiltration of the epidermis, dermis, and or/hypodermis by neutrophils; (2) their association with distinct diseases (eg, hematologic malignancy and chronic inflammatory diseases); (3) potential extracutaneous involvement; and (4) response to anti-inflammatory drugs, such as corticosteroids, dapsone, colchicine, and novel biologic therapies, such as the anti-interleukin-1 blockade. Although distinct NDs have been described, transitional forms with overlapping features are often identified. These justify a simplified classification of NDs with three major forms: superficial (epidermal or pustular) NDs, dermal (en plaques) NDs, and deep NDs. We review selected or novel variants of NDs, including subcorneal pustular dermatosis, the group of immunoglobulin A neutrophilic dermatoses, amicrobial pustular dermatosis of the folds, and neutrophilic urticarial dermatosis, as well as atypical forms of Sweet syndrome and pyoderma gangrenosum closely mimicking severe infectious diseases. Knowledge of these variants is essential for proper diagnosis, adequate management, and avoidance of a dangerous escalation of therapy, such as unnecessary immunosuppression or extensive surgery.

The Cutaneous Spectrum of Lupus Erythematosus

Systemic lupus erythematosus is a complex autoimmune disease with a wide spectrum of clinical and immunopathological features. Cutaneous and articular manifestations are the most common signs in patients with systemic lupus erythematosus. We here review the pathogenesis and the new classification of cutaneous lupus erythemathosus with a discussion of the significance of the various cutaneous signs. The lesions are classified according to the level of the cellular infiltrate and tissue damage in the epidermis, dermis, and/or subcutis. Furthermore, cutaneous lesions pointing to the presence of a thrombotic vasculopathy and those due to a distinct inflammatory, neutrophilic-mediated reaction pattern are highlighted. Particular attention will be given in describing the histology of skin manifestation. Treatment options for cutaneous lupus erythemathosus have increased with the introduction of new biological therapies. However, the majority of the patients still benefit from antimalarials, which remain the cornerstone of treatment. The evaluation and management of cutaneous lupus erythemathosus patients depend on the clinical findings and associated symptoms.

Demodicosis as treatment complication of amicrobial pustulosis of the folds

Amicrobial pustulosis of the folds is a chronic relapsing neutrophilic dermatosis characterized by sterile pustules compromising skin folds, scalp, face and periorificial regions. It predominantly affects women. Demodicosis is an inflammatory disease associated with cutaneous overpopulation of the mite Demodex spp., the pathogenesis of which is not completely established, but is frequently related to local immunodeficiency. A case of a young woman with amicrobial pustulosis of the folds, and isolated worsening of facial lesions, is reported; investigation revealed overlapping demodicosis. There was complete regression of lesions with acaricide and cyclin treatment. This case warns of a poorly diagnosed but disfiguring and stigmatizing disease, often associated with underlying dermatoses or inadvertent treatments on the face.

Drug management of neutrophilic dermatoses

INTRODUCTION

Neutrophilic dermatoses are a heterogenous group of chronic, cutaneous inflammatory conditions characterized by the accumulation of neutrophils in the skin and by systemic inflammation. Neutrophilic dermatoses can be idiopathic or associated with other inflammatory or systemic diseases, including the group of the hereditary, autoinflammatory syndromes. Clinical management is challenging, due to limited clinical evidence and lack of clinical practice guidelines. Areas covered: This review provides an overview of current therapeutic management of the three prototypical neutrophilic dermatoses, aseptic pustulosis of the folds, Sweet syndrome and pyoderma gangrenosum. In addition, we describe innovative, pathogenesis-oriented treatment approaches, which are based on recent advances in the pathophysiology of neutrophilic dermatoses and autoinflammatory syndromes. The increasing role of the IL-1 cytokine family in initiating neutrophilic inflammation in both idiopathic and syndromic disease opened the way for the use of targeted biological treatment. Another promising treatment strategy is aimed at blocking downstream effector cytokines, such as IL12/23 and IL-17, involved in the autoinflammatory immune cascade. Expert commentary: In chronic-recurrent and syndromic cases of neutrophilic dermatoses, there is an unmet clinical need for long-term, continuous disease control. Future controlled clinical studies will optimize the use of targeted-biological agents in sequential or combination treatment strategies.

Cytokine and Chemokine Profile in Amicrobial Pustulosis of the Folds: Evidence for Autoinflammation

Autoinflammation has recently been suggested in the pathogenesis of neutrophilic dermatoses but systematic studies on their cytokine profile are lacking. Notably, amicrobial pustulosis of the folds (APF), classified among neutrophilic dermatoses, has been studied only in small case series. In our University Hospital, we conducted an observational study on 15 APF patients, analyzing their clinical and laboratory features with a follow-up of 9 months to 20 years. Skin cytokine pattern of 9 of them was compared to that of 6 normal controls. In all patients, primary lesions were pustules symmetrically involving the skin folds and anogenital region with a chronic-relapsing course and responding to corticosteroids. Dapsone, cyclosporine, and tumor necrosis factor blockers were effective in refractory cases. In skin samples, the expressions of interleukin (IL)-1β, pivotal cytokine in autoinflammation, and its receptors I and II were significantly higher in APF (P = 0.005, 0.018, and 0.034, respectively) than in controls. Chemokines responsible for neutrophil recruitment such as IL-8 (P = 0.003), CXCL 1/2/3 (C-X-C motif ligand 1/2/3) (P = 0.010), CXCL 16 (P = 0.045), and RANTES (regulated on activation, normal T cell expressed and secreted) (P = 0.034) were overexpressed. Molecules involved in tissue damage like matrix metalloproteinase-2 (MMP-2) (P = 0.010) and MMP-9 (P = 0.003) were increased. APF is a pustular neutrophilic dermatosis with a typical distribution in all patients. The disorder may coexist with an underlying autoimmune/dysimmune disease but is often associated only with a few autoantibodies without a clear autoimmunity. The overexpression of cytokines/chemokines and molecules amplifying the inflammatory network supports the view that APF has an important autoinflammatory component.

Paradoxical Autoinflammatory Skin Reaction to Tumor Necrosis Factor Alpha Blockers Manifesting as Amicrobial Pustulosis of the Folds in Patients With Inflammatory Bowel Diseases

The therapy of inflammatory bowel disease, particularly with tumor necrosis factor (TNF) blockers, may be associated with a number of cutaneous adverse effects, including psoriasis-like, eczema-like, and lichenoid eruptions. Other rare skin complications are neutrophilic dermatoses such as amicrobial pustulosis of the folds (APF), which is a chronic relapsing pustular disorder classified in this spectrum.The authors analyzed clinical, histopathologic, and cytokine expression profiles of 3 inflammatory bowel disease patients with APF triggered by adalimumab (patient 1) and infliximab (patients 2 and 3).All 3 patients presented with sterile pustules involving the cutaneous folds, genital regions, and scalp 6 months after starting adalimumab (patient 1) and 9 months after starting infliximab (patients 2 and 3). Histology was characterized by epidermal spongiform pustules with a dermal neutrophilic and lymphocytic infiltrate. Tumor necrosis factor blocker withdrawal associated with topical and systemic corticosteroids induced complete remission of APF in all 3 patients. The expressions of interleukin (IL)-1 beta and its receptors as well as TNF alpha and its receptors were significantly higher in APF than in controls. Also IL-17, leukocyte selectin, and chemokines, such as IL-8, [C-X-C motif] chemokine ligand 1/2/3 (C = cysteine, X = any amino acid), [C-X-C motif] chemokine ligand 16 (C = cysteine, X = any amino acid), and RANTES (regulated on activation, normal T cell expressed and secreted) were significantly overexpressed. Finally, the authors found significant overexpression of both metalloproteinases 2/9 and their inhibitors 1/2.The observation of 3 patients with APF following anti-TNF therapy expands not only the clinical context of APF but also the spectrum of anti-TNF side effects. Overexpression of cytokines/chemokines and molecules amplifying the inflammatory network supports the view that APF is autoinflammatory in origin.

Lupus miliaris disseminatus faciei in a young male

We report a case of a healthy 26-year-old male with multiple asymptomatic reddish papules and papule-nodules on the central area of the face, persisting from more than 2 months and gradually increasing in number. An incisional skin biopsy revealed a confluent dense granulomatous infiltrate centred by large areas of eosinophilic necrosis consistent with the diagnosis of lupus miliaris disseminatus faciei (LMDF). This is a rare dermatosis first described in 1878 by Fox, that often poses a clinical challenge as it is a disease process which is difficult to diagnose. In fact, in our case, a diagnosis of LMDF was made on skin biopsy. We think that collaboration among dermatologists and General Practitioners is very important for diagnosis of rare dermatosis and especially for management of it, in order to prevent the development of depressed scars.

Neutrophilic skin lesions in autoimmune connective tissue diseases: nine cases and a literature review

The pathophysiology of neutrophilic dermatoses (NDs) and autoimmune connective tissue diseases (AICTDs) is incompletely understood. The association between NDs and AICTDs is rare; recently, however, a distinctive subset of cutaneous lupus erythematosus (LE, the prototypical AICTD) with neutrophilic histological features has been proposed to be included in the spectrum of lupus. The aim of our study was to test the validity of such a classification. We conducted a monocentric retrospective study of 7028 AICTDs patients. Among these 7028 patients, a skin biopsy was performed in 932 cases with mainly neutrophilic infiltrate on histology in 9 cases. Combining our 9 cases and an exhaustive literature review, pyoderma gangrenosum, Sweet syndrome (n = 49), Sweet-like ND (n = 13), neutrophilic urticarial dermatosis (n = 6), palisaded neutrophilic granulomatous dermatitis (n = 12), and histiocytoid neutrophilic dermatitis (n = 2) were likely to occur both in AICTDs and autoinflammatory diseases. Other NDs were specifically encountered in AICTDs: bullous LE (n = 71), amicrobial pustulosis of the folds (n = 28), autoimmunity-related ND (n = 24), ND resembling erythema gyratum repens (n = 1), and neutrophilic annular erythema (n = 1). The improvement of AICTDS neutrophilic lesions under neutrophil targeting therapy suggests possible common physiopathological pathways between NDs and AICTDs.

Pyoderma gangrenosum and systemic lupus erythematosus: a report of five cases and review of the literature

Pyoderma gangrenosum (PG) is an uncommon, distinctive cutaneous ulceration which is usually idiopathic, but may be associated with many systemic disorders. The etiopathogenesis of PG is still not well understood. PG is part of the spectrum of the neutrophilic dermatoses and it has been proposed as a prototype of cutaneous autoinflammatory disease. PG usually has a good outcome under immunosuppressive treatment. Although PG has been associated with several systemic diseases, it has rarely been reported in association with systemic lupus erythematosus (SLE). In this article we report five cases of SLE-related PG and review the literature. Our findings support the possible relationship between active SLE and PG, although the mechanism remains unclear. Clinical manifestations, used treatments and outcomes of SLE-related PG do not differ from the described for the general population.

Neutrophilic dermatoses as systemic diseases

Neutrophilic dermatoses (ND) are inflammatory skin conditions characterized by a sterile infiltrate of normal polymorphonuclear leukocytes. The main clinical forms of ND include Sweet syndrome, pyoderma gangrenosum, erythema elevatum diutinum, subcorneal pustular dermatosis, and their atypical or transitional forms. ND are often idiopathic, but they may be associated with myeloid hematologic malignancies (Sweet syndrome), inflammatory bowel disease or rheumatoid arthritis (pyoderma gangrenosum), and monoclonal gammopathies (erythema elevatum diutinum, subcorneal pustular dermatosis). The possible infiltration of internal organs with neutrophils during the setting of ND underlies the concept of a neutrophilic systemic disease. ND may be seen as a polygenic autoinflammatory syndrome due to their frequent association with other autoinflammatory disorders (monogenic or polygenic) and the recent published efficacy of interleukin-1 blocking therapies in their management.

Erysipelas-like erythema of familial Mediterranean fever syndrome: a case report with emphasis on histopathologic diagnostic clues

We report histopathological findings in a case of familial Mediterranean fever (FMF) syndrome with an erysipelas-like erythema (ELE). ELE is the only pathognomic cutaneous manifestation of FMF. ELE is characterized by well-demarcated, tender, erythematous and infiltrated plaques recurring on the same site and resolving spontaneously within 48-72 h. FMF is a monogenic autoinflammatory syndrome highlighted by recurrent fever associated with polyserositis involving mainly the peritoneum, synovium and pleura. FMF results from a mutation of the MEFV gene, which encodes for pyrin, leading to Il-1β activation and promoting neutrophil migration into the dermis. Histopathological findings in our case showed a sparse superficial perivascular and interstitial lymphocytic infiltrate admixed with some neutrophils, no eosinophils and mild papillary dermal edema. Venules and lymphatics were dilated, though no vasculitis was identified. Neutrophils are the most common cutaneous marker of autoinflammation, and cutaneous manifestations of monogenic autoinflammatory syndromes are represented by the spectrum of aseptic neutrophilic dermatoses. Neutrophils in the presence of recurrent fever and in the correct clinical context of recurrent erysipelas in the same site are a diagnostic clue for FMF.

Inflammatory cells, cytokines and matrix metalloproteinases in amicrobial pustulosis of the folds and other neutrophilic dermatoses

Amicrobial pustulosis of the folds (APF) is a rare cutaneous disease characterized by relapsing sterile pustules frequently associated with autoimmune disorders. Although APF pathophysiology is still undefined, scattered reports suggest involvement of neutrophils. The aim of the present study is to evaluate the role of the skin inflammatory infiltrate, selected multifunctional cytokines and effectors of tissue damage in APF and other neutrophilic dermatoses. We studied, by immunohistochemical methods, inflammatory cell markers (CD3, CD163, myeloperoxidase), cytokines (TNF-alpha, IL-8, IL-17), metalloproteinases (MMP-2, MMP-9) and vascular-endothelial-growth-factor (VEGF) in lesional skin from six patients with APF, 11 with pyoderma gangrenosum (PG), 7 with Sweet's syndrome, and in 20 normal skin samples. Immunoreactivities of CD3, CD163, myeloperoxidase, TNF-alpha, IL-8, IL-17, MMP-2, MMP-9 and VEGF were significantly higher in APF, PG and Sweet's syndrome than in controls (p=0.0001). IL-8 was more expressed in PG than in APF (P=0.002) and Sweet's syndrome (p=0.001). In APF, MMP-9 reactivity was higher than in Sweet's syndrome (p=0.035), but less intense than in PG (p=0.020). Our study supports the role of proinflammatory cytokines/chemokines and MMPs as important effectors for the tissue damage in APF similarly to classic neutrophilic dermatoses.

[Amicrobial pustulosis of the skin folds and autoimmune erythroblastopenia]

INTRODUCTION

Amicrobial pustulosis of the skin folds represents a new entity within the spectrum of neutrophilic dermatoses. This disease is characterized by acute onset of pustular lesions in the skin folds, association with an autoimmune disorder, and improvement under systemic corticosteroids.

OBSERVATION

A 24-year-old woman had been presenting pustular dermatosis for several months involving the inguinal folds and the scalp. The pustules coalesced to form oozing and crusting plaques. Eczematous lesions were located on the trunk. She also presented macrocytic anemia related to autoimmune erythroblastopenia. Bacteriological culture was negative. Antinuclear antibodies were found with anti-SSA specificity. Histopathological examination of a skin biopsy specimen showed pustules in the epidermis together with an inflammatory dermal infiltrate. Cutaneous direct immunofluorescence testing was negative. The patient responded to systemic corticosteroids.

DISCUSSION

Thirty-six cases of amicrobial pustulosis of the skin folds have been reported in the literature. All but two previously reported patients were females with an autoimmune disorder (chiefly systemic lupus erythematosus). The clinical picture is characterized by aseptic pustular lesions of the major and minor skin folds of the scalp and the anogenital area associated with eczematous lesions. Diagnostic criteria have recently been proposed. This disease responds to systemic corticosteroids. We report a new case of amicrobial pustulosis of the skin folds associated with autoimmune erythroblastopenia, which to the best of our knowledge has been described only once in the literature.