Low-dose systemic corticosteroid treatment for recalcitrant hidradenitis suppurativa

S2k‐Leitlinie zur Therapie der Hidradenitis suppurativa/Acne inversa – Kurzfassung

Die S2k‐Leitlinie der Hidradenitis suppurativa/Acne inversa (HS/AI) soll eine akzeptierte Entscheidungshilfe für die Auswahl/Durchführung einer geeigneten/suffizienten Therapie liefern. Hidradenitis suppurativa/Acne inversa ist eine chronisch‐rezidivierende, entzündliche, potenziell mutilierende Hauterkrankung des terminalen Haartalgdrüsenapparats, mit schmerzhaften, entzündlichen Läsionen in den apokrinen drüsenreichen Körperregionen. Ihre Punktprävalenz in Deutschland ist 0,3%, sie wird mit einer Verspätung von 10,0 ± 9,6 Jahren diagnostiziert. Abnormale Differenzierung der Keratinozyten des Haartalgdrüsenapparats und eine begleitende Entzündung bilden die zentrale pathogenetische Grundlage. Primäre HS/AI‐Läsionen sind entzündliche Knoten, Abszesse und drainierende Tunnel. Rezidive in den letzten 6 Monaten mit mindestens zwei Läsionen an den Prädilektionsstellen verweisen auf eine HS/AI mit einer 97‐prozentigen Genauigkeit. HS/AI‐Patienten leiden an einer deutlichen Einschränkung der Lebensqualität. Zur korrekten Therapieentscheidung sollen Klassifikation und Aktivitätsbewertung mit einem validierten Instrument erfolgen, wie dem International Hidradenitis Suppurativa Severity Scoring System (IHS4). Hidradenitis suppurativa/Acne inversa wird nach der Ausprägung der nachweisbaren Entzündung in zwei Formen eingeteilt: aktive, entzündliche (milde, mittelschwere und schwere nach IHS4) und vorwiegend inaktive, nicht entzündliche (Hurley‐Grad‐I, ‐II und ‐III) HS/AI. Orale Tetrazykline oder eine 5‐tägige intravenöse Therapie mit Clindamycin sind mit der Effektivität von Clindamycin/Rifampicin vergleichbar. Subkutan applizierbares Adalimumab, Secukinumab und Bimekizumab sind für die Therapie der HS/AI zugelassen. Für die vorwiegend nicht entzündliche Erkrankungsform stehen verschiedene operative Verfahren zur Verfügung. Medikamentöse/chirurgische Kombinationen gelten als ganzheitliches Therapieverfahren.

S2k guideline for the treatment of hidradenitis suppurativa / acne inversa - Short version

The S2k guideline on hidradenitis suppurativa/acne inversa (HS/AI) aims to provide an accepted decision aid for the selection/implementation of appropriate/sufficient therapy. HS/AI is a chronic recurrent, inflammatory, potentially mutilating skin disease of the terminal hair follicle-glandular apparatus, with painful, inflammatory lesions in the apocrine gland-rich regions of the body. Its point prevalence in Germany is 0.3%, it is diagnosed with a delay of 10.0 ± 9.6 years. Abnormal differentiation of the keratinocytes of the hair follicle-gland apparatus and accompanying inflammation form the central pathogenetic basis. Primary HS/AI lesions are inflammatory nodules, abscesses and draining tunnels. Recurrences in the last 6 months with at least 2 lesions at the predilection sites point to HS/AI with a 97% accuracy. HS/AI patients suffer from a significant reduction in quality of life. For correct treatment decisions, classification and activity assessment should be done with a validated tool, such as the International Hidradenitis Suppurativa Severity Scoring System (IHS4). HS/AI is classified into two forms according to the degree of detectable inflammation: active, inflammatory (mild, moderate, and severe according to IHS4) and predominantly inactive, non-inflammatory (Hurley grade I, II and III) HS/AI. Oral tetracyclines or 5-day intravenous therapy with clindamycin are equal to the effectiveness of clindamycin/rifampicin. Subcutaneously administered adalimumab, secukinumab and bimekizumab are approved for the therapy of HS/AI. Various surgical procedures are available for the predominantly non-inflammatory disease form. Drug/surgical combinations are considered a holistic therapy method.

Taiwanese Dermatological Association (TDA) consensus recommendations for the definition, classification, diagnosis, and management of hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory follicular disease characterized by painful, recurrent, inflamed lesions most commonly occurring in the axillary, inguinal, and anogenital regions. HS can inflict immense physical and psychological impact on patients who suffer from this distressing disease. Management of HS generally requires combining various medical and procedural treatment modalities; however, the disease is often recalcitrant to conventional treatments. In light of recent evidence supporting the effectiveness of biologic agents in the treatment of HS, the Taiwanese Dermatological Association established an expert panel of nine dermatologists to develop consensus statements aimed to provide up-to-date evidence-based guidance in optimizing HS patient management in Taiwan. The recommendations described in the statements were summarized in a management algorithm in terms of general care, topical treatment, systemic treatment, and procedural treatment.

Efficacy and Patient Satisfaction Associated With Intramuscular Triamcinolone Therapy for Acute Flares of Hidradenitis Suppurativa

BACKGROUND

A lack of consensus exists regarding acute flare management in hidradenitis suppurativa (HS). Intramuscular triamcinolone (IMTAC) therapy is useful in numerous inflammatory conditions; however, it has not been investigated for acute HS flares.

OBJECTIVE

To evaluate the efficacy and patient experience associated with IMTAC therapy for acute, severe HS flares.

METHODS

Retrospective analysis and surveys of 45 HS patients were conducted at Albert Einstein College of Medicine/ Montefiore HS Center, Bronx, NY, USA.

RESULTS

Follow-up visits 6.77 (4.45) weeks after IMTAC therapy revealed significant reductions in mean HS-Physician Global Assessment (PGA) (P < .001), C-Reactive Protein (CRP) (P = .03), increased hemoglobin (P = .004), and improved pain scores (P < .001). Adjusting for age, sex and concomitant medications, multivariate analysis yielded significantly reduced pain (P = .02) and increased hemoglobin (P = .03). Patient surveys indicate that IMTAC was well-tolerated, as reflected in positive mean responses for satisfaction (29 [64%]) and willingness to receive IMTAC injections again (42 [93%]).

CONCLUSIONS

These novel findings demonstrate that IMTAC is a safe, effective, and well accepted adjunct for acute HS management.

Practical Guidelines for Managing Patients With Hidradenitis Suppurativa: An Update

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease that is characterized by the formation of comedones, papules, nodules, abscesses and sinus tracts in the axillary, inframammary, groin, and gluteal areas. Up to 3.8% of the Canadian population has HS, though due to a lack of awareness of HS, many patients are initially misdiagnosed and do not receive adequate treatment early on in the disease course. Once a diagnosis of HS is made, developing an effective management plan can be a dilemma for many providers. There is significant variability in response to any given therapy within the HS patient population and many HS patients have other medical comorbidities which must be taken into consideration. The aim of this review is to provide a practical approach for all healthcare providers to diagnose and manage HS and its associated comorbidities. A sample electronic medical record template for HS management was developed by the Canadian Hidradenitis Suppurativa Foundation Executive Board and is intended for use in clinical settings. This will help to increase collaboration between primary healthcare providers, dermatologists, and other medical specialists and ultimately improve the quality of care that HS patients receive.

Advances in molecular pathogenesis of hidradenitis suppurativa: Dysregulated keratins and ECM signaling

Hidradenitis suppurativa (HS) is characterized by deep-seated, highly inflamed, and painful lumps/abscesses, fistulae, and sinus tracts that grow extensively deep in the dermis and are highly immunogenic in nature. In about one-third of the HS patients there is strong evidence for the role of γ-secretase mutations along with dysregulated Notch signaling. However, the contribution of dysregulated Notch signaling in HS pathogenesis in relation to hair follicle alterations and hyper-activation of the immune system remains undefined. A genome-wide association study (GWAS), proteomic data and functional investigations of identified sequence variants in HS pathology are not fully revealing. The disease initiation or progression may involve bacterial infection besides intrinsic functional defects in keratinocytes, which may be key to further exacerbate immune cell infiltration and cytokine production in and around the lesional tissue. The absence of a suitable animal model that could fully recapitulate the pathogenesis of HS is a major impediment for proper understanding the underlying mechanisms and development of effective treatments. The presence of extracellular matrix (ECM) degradation products along with dysregulation in keratinocytes and, dermal fibroblasts ultimately affect immune regulation and are various components of HS pathogenesis. Bacterial infection further exacerbates the complexity of the disease progression. While anti-TNFα therapy shows partial efficacy, treatment to cure HS is absent. Multiple clinical trials targeting various cytokines, complement C5a and ECM products are in progress. This review provides state-of-the-art information on these aspects with a focus on dysregulated keratinocyte and immune cells; and role of ECM, and Keratin functions in this regard.

Efficacy and Toxicity of Classical Immunosuppressants, Retinoids and Biologics in Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory disorder of the apocrine glands characterized by recurrent episodes. Although several therapies exist, none is completely curative. Several immunosuppressives have been studied with encouraging results and targeted approaches. In this review, we highlight the various immunosuppressives used in this condition along with their salient features to enable physicians to choose the correct therapy for their patients. The search of the peer-reviewed literature included clinical trials, scientific reviews, case series, case reports, and guidelines. The literature was identified from electronic databases (MEDLINE and PubMed) through November 2021; additional articles were included from the references of the identified articles.

A Case of Pemphigus Vulgaris and Hidradenitis Suppurativa: May Systemic Steroids Be Considered in the Standard Management of Hidradenitis Suppurativa?

<b><i>Introduction:</i></b> Recent studies have demonstrated a correlation between pemphigus and hidradenitis suppurativa (HS). <b><i>Case Presentation:</i></b> Here, we report the case of a 58-year-old man affected by HS for about 30 years who was found to have lesions attributable to pemphigus during a checkup. <b><i>Discussion/Conclusion:</i></b> There are few data in the literature on the use of systemic corticosteroids for the two diseases, and our article wants to be a food for thought on the management and treatment of these diseases.

New perspectives on the treatment of hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease characterized by the presence of painful nodules, abscesses, chronically draining fistulas, and scarring in apocrine gland-bearing areas of the body. The exact pathogenesis of HS is not yet well understood, but there is a consensus in considering HS a multifactorial disease with a genetic predisposition, an inflammatory dysregulation, and an influence of environmental modifying factors. Therapeutic approach of HS is challenging due to the wide clinical manifestations of the disease and the complex pathogenesis. This review describes evidence for effectiveness of current and emerging HS therapies. Topical therapy, systemic treatments, biological agents, surgery, and light therapy have been used for HS with variable results. Adalimumab is the only US Food and Drug Administration (FDA) approved biologic agent for moderate-to-severe HS, but new therapeutic options are being studied, targeting different specific cytokines involved in HS pathogenesis. Comparing treatment outcomes between therapies is difficult due to the lack of randomized controlled trials. Treatment strategy should be selected in concordance to disease severity and requires combination of treatments in most cases.

Hidradenitis suppurativa: Basic considerations for its approach: A narrative review

Hidradenitis suppurativa is a chronic and debilitating skin disease, whose lesions can range from inflammatory nodules to abscesses and fistulas in the armpits, groin, perineum, inframammary region. Diagnosis can be confused with a large number of clinical pictures, and although studies on hidradenitis suppurativa are not so scarce in the literature, doctors are often unaware of this disease and therefore its diagnosis is often late. Pharmacological treatment ranges from retinoids to immunosuppression and radiation therapy, and surgical treatment ranges from incision and drainage to more complete excisions and laser therapies. Hidradenitis suppurativa is a disease seen and treated mainly by dermatologists and general surgeons, however, it is necessary for general practitioners to have basic knowledge about this entity, as they are the first line of care in the health system.

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Hidradenitis suppurativa is an entity of necessary recognition by the surgeon.

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It is a preventable and treatable condition with a good prognosis.

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This condition should be managed by a multidisciplinary team.

Clinical Epidemiology and Management of Hidradenitis Suppurativa

Hidradenitis suppurativa is a chronic immune-mediated inflammatory skin disease with a prevalence of 0.1-1%, characterized by nodules and abscesses in the axillae, groin, and inframammary areas, sometimes developing into tunnels (or fistulas) and scars. Because hidradenitis suppurativa is more common in women and in those aged 18-40 years, obstetrician-gynecologists (ob-gyns) have the opportunity to diagnose, educate, initiate treatment, and coordinate care with ancillary health care professionals. The recently published North American treatment guidelines, along with management information for patients with hidradenitis suppurativa who are pregnant or breastfeeding, are summarized. By diagnosing and optimizing hidradenitis suppurativa treatment early in the disease course, ob-gyns can reduce morbidity, with the potential to favorably alter disease trajectory.

[Hidradenitis suppurativa/acne inversa in daily practice]

Hidradenitis suppurativa (HS) is a chronic inflammatory disease, characterized by abscess formation and mutilating scar formation in the body folds. The burden of disease is high for both patient and treating physician. In dermatological daily practice, proper patient education and formation of a trustful physician-patient relationship are of highest importance. HS patients are treated both conservatively and surgically mostly by dermatologists, which requires extensive knowledge of the pathogenesis, trigger factors, comorbidities and treatment options. Interdisciplinary collaboration with other disciplines is still underdeveloped. New physical treatments (laser, radiofrequency, intense pulsed light [IPL]), topical and systemic therapies enable good ambulatory long-term management for all HS stages.

Emerging medical treatments for hidradenitis suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory disease affecting intertriginous skin areas, and it is characterized by recurrent painful episodes of inflammatory drainage. Although the pathophysiology of HS is not fully understood, recent research points to an imbalance of cytokines as a contributing factor to the associated symptoms of purulent drainage and sinus tract formation. HS lesions are often characterized by a superimposed pathogenic/commensal bacterial infection that can improve with targeted antibiotic therapy. New medical treatments have emerged in recent years, many of which specifically work against a variety of proinflammatory mediators associated with HS. These newer, specified treatment options, in conjunction with surgery and lasers, are thought to provide positive outcomes and an overall improvement in quality of life in patients with HS.

Tuscan consensus on the diagnosis and treatment of hidradenitis suppurativa

BACKGROUND

A rationalized model of clinical and therapeutic management of hidradenitis suppurativa (HS) should place the patients at the heart of the process, facilitating their access to diagnostic tests and treatments, providing the appropriate care for each grade of disease severity and optimizing the use of healthcare resources, both in economic and human terms.

MATERIAL AND METHODS

This paper reports the results of a Consensus of the Tuscany HS working group for a rationalized model of diagnosis and management of HS.

RESULTS

The diagnostic and therapeutic protocols, the available technological equipments and the management models, are presented in the light of today's scientific evidence.

CONCLUSION

The goal of the Consensus is to bring the issue of HS management to the attention of the Tuscan regional government, in order to create unanimously accepted diagnostic and therapeutic protocols.

Hidradenitis suppurativa: Current and emerging treatments

The treatment of hidradenitis suppurativa (HS) has remained challenging because of the many knowledge gaps regarding etiology. However, recent studies into the pathogenesis of HS have enabled the investigation of newer therapies. The second article in this continuing medical education series reviews the evidence for established therapies for HS, including anti-inflammatories, antibiotics, and surgery. New and emerging therapies that specifically target cytokines involved in HS pathogenesis will be covered. The potential therapeutic roles of anticytokine therapies, including both the expanded application of existing molecules as well as the specific development of novel therapies for HS are discussed. With increased attention on HS and with numerous clinical trials currently underway, we hope that the variety of treatment options for HS will be expanded.

North American clinical management guidelines for hidradenitis suppurativa: A publication from the United States and Canadian Hidradenitis Suppurativa Foundations: Part II: Topical, intralesional, and systemic medical management

Hidradenitis suppurativa is a severe and debilitating dermatologic disease. Clinical management is challenging and consists of both medical and surgical approaches, which must often be combined for best outcomes. Therapeutic approaches have evolved rapidly in the last decade and include the use of topical therapies, systemic antibiotics, hormonal therapies, and a wide range of immunomodulating medications. An evidence-based guideline is presented to support health care practitioners as they select optimal medical management strategies and is reviewed in this second part of the management guidelines. A therapeutic algorithm informed by the evidence available at the time of the review is provided.

The anti-inflammatory potency of biologics targeting tumour necrosis factor-α, interleukin (IL)-17A, IL-12/23 and CD20 in hidradenitis suppurativa: an ex vivo study

Background

Biologics targeting inflammatory mediators can achieve clinical improvements in hidradenitis suppurativa (HS). However, their clinical efficacy shows great interpatient variability in daily practice.

Objectives

To investigate the anti‐inflammatory potency of a selection of currently available biologics and prednisolone for the treatment of HS in an ex vivo skin culture system using lesional HS biopsies.

Methods

Lesional skin samples from 10 patients with HS and skin samples from five healthy controls were cultured ex vivo and exposed to prednisolone or biologics targeting tumour necrosis factor (TNF)‐α, interleukin (IL)‐17A, IL‐12/23p40 or CD20 (adalimumab, infliximab, secukinumab, ustekinumab and rituximab, respectively). Real‐time quantitative polymerase chain reaction and cytokine bead arrays were used to measure the inhibitory effect of the biologics on cytokines and antimicrobial peptides (AMPs).

Results

The relative mRNA expression of all tested cytokines and AMPs was significantly downregulated by all anti‐inflammatory agents (P < 0·001). The protein production of the proinflammatory cytokines TNF‐α, interferon γ, IL‐1β, IL‐6 and IL‐17A was significantly inhibited by adalimumab, infliximab, ustekinumab, prednisolone (all P < 0·001) and rituximab (P = 0·0071), but not by secukinumab (P = 0·0663). On both mRNA and protein levels, adalimumab, infliximab and prednisolone reduced the levels of a broader mix of individual cytokines than secukinumab, ustekinumab and rituximab. Moreover, a significant inhibitory effect on mRNA expression levels of inflammatory markers in healthy control skin was observed only for TNF‐α inhibitors (P < 0·001) and prednisolone (P = 0·0015).

Conclusions

This ex vivo study suggests that TNF‐α inhibitors and prednisolone are the most powerful inhibitors of proinflammatory cytokines and AMPs in HS lesional skin, which concurs with our clinical experience in patients with HS.

What's already known about this topic?

A key element of hidradenitis suppurativa (HS) is an aberrant immune response characterized by the overexpression of several proinflammatory cytokines and antimicrobial peptides in lesional skin.

Biologics targeting inflammatory cytokines have the potential to improve HS disease activity.

There is still need for efficacious drugs in the treatment of HS.

What does this study add?

We sought to quantify the anti‐inflammatory effects of currently available biologics in an ex vivo disease model.

Adalimumab, infliximab, secukinumab, ustekinumab and rituximab in addition to prednisolone significantly inhibited a selected panel of proinflammatory cytokines and antimicrobial peptides in ex vivo HS lesional skin.

Adalimumab, infliximab and prednisolone reduced the levels of a broader mix of individual cytokines than secukinumab, ustekinumab and rituximab.

What is the translational message?

The significant inhibition of important proinflammatory cytokines by tumour necrosis factor‐α inhibitors in HS correlates with their clinical efficacy.

Our ex vivo skin culture system represents an adequate model for studies in search of novel candidate drugs for the treatment of HS and to personalize the treatment in specific patients.

Linked Comment: https://doi.org/10.1111/bjd.18173.

https://www.bjdonline.com/article/

Topical, systemic and biologic therapies in hidradenitis suppurativa: pathogenic insights by examining therapeutic mechanisms

Hidradenitis suppurativa (HS) is a chronic inflammatory disease of the skin, manifesting in chronic, recurrent painful pustules, nodules, boils and purulent draining abscesses. Our current understanding of the pathogenesis of the disease is incomplete. This review aims to identify available treatment options in HS and discuss the pharmacological mechanisms through which such agents function. Identifying common pathways may inform our understanding of the pathogenesis of HS as well as identify future therapeutic targets. The pharmacological mechanisms implicated in topical therapies, antibiotic, hormonal, systemic immunomodulatory and biologic therapies for HS are discussed. Significant differences exist between agents and implicated pathways in therapy for mild and severe disease. This is an expression of the possible dichotomy in inflammatory pathways (and treatment responses) in HS. Studies involving monoclonal antibodies provide the greatest insight into what these specific mechanisms may be. Their variable levels of clinical efficacy compared with placebo bolsters the suggestion that differential inflammatory pathways may be involved in different presentations and severity of disease. Nuclear factor kappa B (NF-κB), tumor necrosis factor (TNF)-α and other innate immune mechanisms are strongly represented in treatments which are effective in mild to moderate disease in the absence of scarring or draining fistulae, however complex feed-forward mechanisms in severe disease respond to interleukin (IL)-1 inhibition but are less likely to respond to innate immune inhibition (through NF-κB or TNF-α) alone. It is unclear whether IL-17 inhibition will parallel TNF-α or IL-1 inhibition in effect, however it is plausible that small molecule targets (Janus kinase1 and phosphodiesterase 4) may provide effective new strategies for treatment of HS.

Hidradenitis suppurativa/acne inversa: a practical framework for treatment optimization - systematic review and recommendations from the HS ALLIANCE working group

Hidradenitis suppurativa (HS)/acne inversa is a debilitating chronic disease that remains poorly understood and difficult to manage. Clinical practice is variable, and there is a need for international, evidence‐based and easily applicable consensus on HS management. We report here the findings of a systematic literature review, which were subsequently used as a basis for the development of international consensus recommendations for the management of patients with HS. A systematic literature review was performed for each of nine clinical questions in HS (defined by an expert steering committee), covering comorbidity assessment, therapy (medical, surgical and combinations) and response to treatment. Included articles underwent data extraction and were graded according to the Oxford Centre for Evidence‐based Medicine criteria. Evidence‐based recommendations were then drafted, refined and voted upon, using a modified Delphi process. Overall, 5310 articles were screened, 171 articles were analysed, and 65 were used to derive recommendations. These articles included six randomized controlled trials plus cohort studies and case series. The highest level of evidence concerned dosing recommendations for topical clindamycin in mild disease (with systemic tetracyclines for more frequent/widespread lesions) and biologic therapy (especially adalimumab) as second‐line agents (following conventional therapy failure). Good‐quality evidence was available for the hidradenitis suppurativa clinical response (HiSCR) as a dichotomous outcome measure in inflammatory areas under treatment. Lower‐level evidence supported recommendations for topical triclosan and oral zinc in mild‐to‐moderate HS, systemic clindamycin and rifampicin in moderate HS and intravenous ertapenem in selected patients with more severe disease. Intralesional or systemic steroids may also be considered. Local surgical excision is suggested for mild‐to‐moderate HS, with wide excision for more extensive disease. Despite a paucity of good‐quality data on management decisions in HS, this systematic review has enabled the development of robust and easily applicable clinical recommendations for international physicians based on graded evidence.

Current and future treatment of hidradenitis suppurativa

This scholarly review on the current and future treatment of hidradenitis suppurativa (HS) focuses on medical and surgical treatment options, while novel pipeline drugs are also discussed. Treatment goals are to limit the incidence and duration of flares, reducing inflammation and suppuration, achieving local cure after surgery and, most importantly, to improve the quality of life of patients with HS. The type of medication and/or surgery should be chosen based on the stage of the disease and the degree of inflammation. However, the lack of a simple scoring system and the lack of clear surgical outcome definitions hamper the interpretation of treatment efficacy and the comparison between different treatment strategies. The therapeutic pipeline for HS is gradually expanding, and will probably lead to a broader panel of more effective therapeutic options.

Review of Current Immunologic Therapies for Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic, recurrent, inflammatory disease of apocrine gland-bearing skin which affects approximately 1-4% of the population. The disease is more common in women and patients of African American descent and approximately one-third of patients report a family history. Obesity and smoking are known risk factors, but associations with other immune disorders, especially inflammatory bowel disease, are also recognized. The pathogenesis of HS is poorly understood and host innate or adaptive immune response, defective keratinocyte function, and the microbial environment in the hair follicle and apocrine gland have all been postulated to play a role in disease activity. While surgical interventions can be helpful to reduce disease burden, there is a high recurrence rate. Increasingly, data supports targeted immune therapy for HS, and longitudinal studies suggest benefit from these agents, both when used alone and as an adjunct to surgical treatments. The purpose of this review is to outline the current data supporting use of targeted immune therapy in HS management.

The critical role of macrophages in the pathogenesis of hidradenitis suppurativa

INTRODUCTION

Hidradenitis suppurativa (HS) is a painful chronic inflammatory disease with a prevalence between 1 and 4% of general population. The pathogenesis of HS long eluded scientists, but growing evidence suggests that it is a consequence of inflammatory dysregulation.

FINDINGS

Recent studies suggest that dysregulated immune response to skin flora and overexpression of inflammatory cytokines leads to chronic skin inflammation seen in HS. Macrophages are the most numerous inflammatory cells found in HS infiltrates and release numerous pro-inflammatory cytokines such as IL-23, and IL-1β and TNF-α, exacerbating the inflammation and contributing to the pathogenesis of HS. Furthermore, in HS, there is dysregulated function of other immune players closely associated with macrophage function including: matrix metalloproteases (MMP) 2 and 9 overexpression, toll-like receptor upregulation, impaired Notch signalling, NLRP3 inflammasome upregulation, and dysregulated keratinocyte function. Lifestyle factors including obesity and smoking also contribute to macrophage dysfunction and correlate with HS incidence.

CONCLUSIONS

The overexpression of pro-inflammatory cytokines and subsequent efficacy of anti-cytokine biologic therapies highlights the importance of managing macrophage dysfunction. Future therapies should target key molecular drivers of macrophage dysfunction such as TLR2 and NLRP3 overexpression.