A systematic review and critical evaluation of inflammatory cytokine associations in hidradenitis suppurativa

Neutrophil extracellular traps activate Notch-γ-secretase signaling in hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is an inflammatory chronic skin disorder of unknown etiology characterized by inflamed abscess-like nodules and boils resulting in sinus tract formation, tissue scarring, and massive infiltration of neutrophils. Multiple lines of evidence have highlighted the potential association between alterations in the Notch pathway and HS pathogenesis, but the mechanisms remain incompletely characterized.

OBJECTIVE

We aimed to elucidate the role of neutrophil extracellular traps in Notch-γ-secretase signaling.

METHODS

Twenty-six HS lesional tissues, primary HS macrophages, and skin fibroblasts were interrogated by quantitative PCR, Western blot, and ELISA analyses. γ-Secretase and TNF-α converting enzyme activities were measured in HS skin lesions, macrophages, and skin fibroblasts. Immunofluorescence and RNAscope analyses were performed in HS and control skin.

RESULTS

A prominent presence of Notch ligands, Delta-like ligand 4 (DLL4), and Jagged (JAG) 2 were detected at the protein and mRNA levels in HS skin lesion compared to control. Levels of DLL4, JAG1, citrullinated histone H3 DNA, and γ-secretase activity correlated with HS disease severity. Additionally, significantly elevated levels of Notch ligands and γ-secretase activity were found in dissected sinus tracts compared to the rest of HS tissue. Immunofluorescence microscopy of HS skin lesions revealed activation of Notch-1 signaling in macrophages and skin fibroblasts. Neutrophil extracellular traps (NETs) purified from HS patients displayed elevated levels of DLL4. HS NETs activated the Notch pathway in macrophages and dermal fibroblasts isolated from HS patients. HS skin fibroblasts displayed elevated levels of CD90 and DPP4 in association with increased migratory capacity and Notch activation. Inhibition of Notch decreased migratory capacity and profibrotic markers in HS fibroblasts.

CONCLUSION

These data support a pathogenic connection between NETs, Notch-γ-secretase activation, and the release of profibrotic molecules that promote dysregulation of macrophages and skin fibroblasts in HS. Unveiling the relevance of these molecular events not only expands our understanding of HS but also opens new venues for the development of targeted therapies to address the fibrotic complications of advanced stages of HS.

Setting the Stage for Standardized Reporting of Clinical and Demographic Information in Laboratory-Based Studies of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a complex inflammatory skin condition affecting 0.1-4% of the population that leads to permanent scarring in the axilla, inframammary region, groin, and buttocks. Its complex pathogenesis involves genetics, innate and adaptive immunity, microbiota, and environmental stimuli. Specific populations have a higher incidence of HS, including females and Black individuals and those with associated comorbidities. HS registries and biobanks have set standards for the documentation of clinical data in the context of clinical trials and outcomes research, but collection, documentation, and reporting of these important clinical and demographic variables are uncommon in HS laboratory research studies. Standardization in the laboratory setting is needed because it helps to elucidate the factors that contribute mechanistically to HS symptoms and pathophysiology. The purpose of this article is to begin to set the stage for standardized reporting in the laboratory setting. We discuss how clinical guidelines can inform laboratory research studies, and we highlight what additional information is necessary for the use of samples in the wet laboratory and interpretation of associated mechanistic data. Through standardized data collection and reporting, data harmonization between research studies will transform our understanding of HS and lead to novel discoveries that will positively impact patient care.

Genetic factors associated with hidradenitis suppurativa, a literature review

Background

Hidradenitis suppurativa (HS) is a chronic inflammatory disease characterized by deep-seated, painful lesions most frequently occurring in intertriginous areas of the skin. HS leads to poor quality of life in affected individuals and is difficult to diagnose and treat.

Objective

Understanding the genetics associated with familial inheritance may lead to a better understanding of the pathogenesis of this debilitating disease.

Methods

Articles published until March 9, 2023, were identified in PubMed using the following search terms: hidradenitis suppurativa and gene* or acne inversa and gene*.

Results

The rate of monogenic mutations associated with HS is less than 7%, with the most common genetic mutations reported in sporadic and familial HS cases being in NCSTN and less frequently in PSENEN. Individuals with mutations in the gamma-secretase complex tended to have more severe HS and an early age of onset.

Limitations

This study was limited to the case studies available in PubMed, the majority of which used targeted gene panels to detect genetic mutations.

Conclusion

Approximately 30% of individuals diagnosed with HS report having a positive family history; however, very few studies demonstrate monogenic familial transmission of HS. The case studies of syndromic HS reported a variety of genetic mutations associated with HS, some of which were familial, while others were sporadic, suggesting that other pathways may be involved in the pathogenesis of HS and other potential mutations that have yet to be evaluated. More research is needed to understand the genetic mutations in HS.

Orismilast for the treatment of mild to severe hidradenitis suppurativa: Week 16 data from OSIRIS, a Phase 2a, open-label, single-centre, single-arm, dose-finding clinical trial

BACKGROUND

Hidradenitis suppurativa (HS) is a disease with an unmet need for treatment.

OBJECTIVE

To examine tolerability, safety and efficacy of oral phosphodiesterase-4 (PDE4) inhibitior orismilast 10-40 mg twice daily (BID) in HS.

METHODS

A Phase 2a, single-arm, single-centre, open-label, 16-week trial in HS patients. Adjustments in maximal dose and titration were allowed, to improve tolerability, dividing the study population in two groups who completed and discontinued 16 weeks of treatment. Descriptive statistics were applied to efficacy data from patients who completed treatment and patients who discontinued treatment prematurely. A last-observation-carried-forward (LOCF) approach was used for patients who discontinued treatment. The primary endpoint was percent change in the total number of abscesses and nodules (AN-count) at Week 16, with the HS Clinical Response with a 50% reduction in the AN-count (HiSCR50) as key secondary endpoint.

RESULTS

Of the 20 patients included, 9 completed 16 weeks of treatment and 11 discontinued treatment prematurely. The mean AN-count was reduced with 33.1% in patients who completed treatment and with 12.0% in patients who discontinued. HiSCR50 was achieved by 67.0% and 27.0% of patients who completed and discontinued treatment, respectively. Most adverse events were mild to moderate.

CONCLUSIONS

Oral orismilast demonstrated a dose-dependent tolerability, with mild to moderate adverse effects. Further, the results of this exploratory trial indicate that orismilast may lead to clinical improvements in HS. However, larger trials with tolerable dose ranges are warranted. The Trial is registered at Clinicaltrials.gov (UNI50007201) and EudraCT.ema.europa.eu (2021-000049-42).

Brepocitinib, Zimlovisertib, and Ropsacitinib in Hidradenitis Suppurativa

BACKGROUND: Hidradenitis suppurativa (HS) is a debilitating, inflammatory skin disease with limited treatment options and partially understood pathophysiology. Using an umbrella trial design, three kinase inhibitor immunomodulators with different mechanisms of action were evaluated. METHODS: This phase 2a, double-blind, parallel-group trial enrolled adults with moderate to severe HS who were then randomly assigned (1:1:1:1) to once-daily brepocitinib 45 mg (a JAK1/TYK2 inhibitor), zimlovisertib 400 mg (an IRAK4 inhibitor), ropsacitinib 400 mg (a TYK2 inhibitor), or matching placebo for 16 weeks. The primary end point was the percentage of participants achieving HS clinical response (HiSCR) at week 16. Safety, including treatment-emergent adverse events (TEAEs), was monitored throughout. RESULTS: Totals of 52, 47, 47, and 48 participants were assigned to brepocitinib, zimlovisertib, ropsacitinib, and placebo, respectively. At week 16, 28% were lost to follow-up and assumed to be nonresponders; HiSCR occurred in 33.3% (16/48) of participants receiving placebo and in 51.9% (27/52), 34.0% (16/47), and 37.0% (17/46) of those receiving brepocitinib, zimlovisertib, and ropsacitinib (difference in percentage points vs. placebo [90% confidence interval], 18.7 [2.7 to 34.6], 0.7 [−15.2 to 16.7], and 3.5 [−12.6 to 19.6]), respectively. TEAEs occurred more frequently with active treatment (brepocitinib, 30 [57.7%]; zimlovisertib, 26 [55.3%]; ropsacitinib, 29 [61.7%]; placebo, 23 [47.9%]). Most TEAEs (infections, skin disorders, and gastrointestinal symptoms) were mild; there were no deaths. CONCLUSIONS: Participants with moderate to severe HS treated with brepocitinib experienced greater clinical response, whereas those on zimlovisertib and ropsacitinib did not, compared with placebo. These results favor the JAK/STAT pathway as an immunologic target in HS and did not confirm a role for selective IRAK4 or TYK2 inhibition. These results should be confirmed in larger studies with longer follow-up. (Funded by Pfizer; ClinicalTrials.gov registration number, NCT04092452.)

Narrative Review and Update on Biologic and Small Molecule Drugs for Hidradenitis Suppurativa: An Entity With a Promising Future

Hidradenitis suppurativa (HS) is a chronic inflammatory entity characterized by the appearance of multiple nodules, abscesses, and fistulas, predominantly in apocrine regions. In addition to its dermatological involvement, it is associated with multiple systemic comorbidities. Its treatment is combined: topical pharmacological, systemic pharmacological and surgical. Regarding biologic or small molecule drugs, currently only adalimumab is approved. A narrative review of the literature on biological or small molecule drugs used in the treatment of hidradenitis suppurativa is presented. The arsenal we found is large, with multiple targets: inhibitors of tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-17, IL-23, IL-1, inhibitors of the janus kinase (JAK) pathway, and multiple other drugs in study. New prospective studies and comparative trials are needed to analyze the effectiveness and safety of these treatments, in an entity with a promising future.

Narrative Review and Update on Biologic and Small Molecule Drugs for Hidradenitis Suppurativa: An Entity With a Promising Future

Hidradenitis suppurativa (HS) is a chronic inflammatory entity characterized by the appearance of multiple nodules, abscesses, and fistulas, predominantly in apocrine regions. In addition to its dermatological involvement, it is associated with multiple systemic comorbidities. Its treatment is combined: topical pharmacological, systemic pharmacological and surgical. Regarding biologic or small molecule drugs, currently only adalimumab is approved. A narrative review of the literature on biological or small molecule drugs used in the treatment of hidradenitis suppurativa is presented. The arsenal we found is large, with multiple targets: inhibitors of tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-17, IL-23, IL-1, inhibitors of the janus kinase (JAK) pathway, and multiple other drugs in study. New prospective studies and comparative trials are needed to analyze the effectiveness and safety of these treatments, in an entity with a promising future.

A proof-of-concept open-label clinical trial of spleen tyrosine kinase antagonism using fostamatinib in moderate-to-severe hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is an autoinflammatory disorder of keratinization with a prominence of B cells and plasma cells. Fostamatinib is a spleen tyrosine kinase inhibitor targeting B cells and plasma cells.

OBJECTIVES

To assess the safety, tolerability, and clinical response at week 4 and week 12 of fostamatinib in moderate-to-severe HS.

METHODS

Twenty participants were administered fostamatinib 100 mg twice a day for 4 weeks, escalating to 150 mg twice a day thereafter until week 12. Participants were assessed for adverse events and clinical response assessed by HiSCR (Hidradenitis Suppurativa Clinical Response Score) and IHS4 (International Hidradenitis Suppurativa Severity Score) as well as other outcomes including DLQI (Dermatology Life Quality Index), visual analog scale, and physician global assessment.

RESULTS

All 20 participants completed the week 4 and week 12 endpoints. Fostamatinib was well tolerated in this cohort with no grade 2/3 adverse events reported. A total of 85% achieved HiSCR at week 4 and 85% at week 12. The greatest reduction in disease activity was seen at weeks 4/5 with worsening in a proportion of patients thereafter. Significant improvements were seen in pain, itch, and quality of life.

CONCLUSIONS

Fostamatinib was well tolerated in this HS cohort with no serious adverse events and improvement in clinical outcomes. Targeting B cells/plasma cells may be a viable therapeutic strategy in HS and requires further exploration.

The genetic aspects of hidradenitis suppurativa

Genetic aspects have a substantial role in hidradenitis suppurativa (HS) pathogenesis. A positive family history of HS occurs in about one-third of HS cases and is significantly higher in patients with early onset of the disease. Recent twin studies have shown a high heritability in HS, fortifying the importance of genetic factors in disease pathogenesis. Based on existing knowledge on the genomics of HS, the disease can be categorized as familial HS, sporadic, syndromic HS, and "HS plus" associated with other syndromes. In familial HS, autosomal dominant transmission is proposed, and monogenic inheritance is rare. This monogenic trait is related to mutations of γ-secretase component genes and Notch signaling or defects in inflammasome function. With newly discovered gene mutations, such as those related to innate and adaptive immunity, skin microbiome, inflammasome, epidermal homeostasis, and keratinization pathway, we can define HS as a polygenic, multifactorial, autoinflammatory disease. To fully elucidate the genetic aspects of HS, we need extensive, long-term global collaborations.

Risk of Chronic Kidney Disease in Hospitalized Patients with Hidradenitis Suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) is associated with several comorbidities such as diabetes mellitus and cardiovascular diseases. These comorbidities are also risk factors for chronic kidney disease (CKD), yet little is known about the risk of CKD in HS patients.

OBJECTIVES

The objective was to study the prevalence of CKD in HS patients.

METHODS

Cross-sectional population-based study using the United States National Inpatient Sample database between January 1, 2002 and December 31, 2012 was performed.

RESULTS

We identified 23,767 hospital admissions for HS patients and 95,068 admissions for age- and gender-matched controls. The prevalence of CKD in HS patients was 6.3% (1,497/23,767) compared to non-HS controls which was 4.3% (4,052/95,068). The association of CKD was strongest in HS patients, who were ≥60 years old, 16.9% (475/2,811), male 7.3% (695/9,556), obese 7.8% (407/5,209), diabetic 12.5% (890/7,105), hyperlipidemic 13.3% (416/3,126), and had cardiovascular diseases 12.5% (631/5,045). The crude odds ratio of CKD in HS patients was 1.5 (95% CI: 1.420-1.605) compared to non-HS patients. The association remained significant after adjusting for important covariates with adjusted odds ratio of CKD in HS patients of 1.1 (95% CI: 1.014-1.176) compared to non-HS patients.

CONCLUSIONS

Our findings show that there is a possible association of HS with CKD. Any signs of CKD should be assessed by a nephrologist as early diagnosis can hopefully prevent further progression.

Metformin Treatment of Hidradenitis Suppurativa: Effect on Metabolic Parameters, Inflammation, Cardiovascular Risk Biomarkers, and Immune Mediators

Hidradenitis suppurativa (HS) is a common cutaneous and systemic inflammatory disease with a significant impact on mental health and quality of life. It is associated with obesity, insulin resistance, metabolic syndrome, cardiovascular (CV) disease, and increased all-cause mortality. Metformin is used frequently in HS treatment and is effective for some patients. The mechanism of action of metformin in HS is unknown. A case-control study of 40 patients with HS (20 on metformin and 20 controls) was conducted to assess differences in metabolic markers, inflammation (C-reactive protein [CRP], serum adipokines, and CV risk biomarkers), and serum immune mediators. Body mass index (BMI), insulin resistance (77%), and metabolic syndrome (44%) were high overall, but not significantly different between the groups. This highlights the need for co-morbidity screening and management. A significant reduction in fasting insulin and a trend towards a reduction in insulin resistance were identified in the metformin group compared with pre-treatment levels. CV risk biomarkers were significantly favourable in the metformin group (lymphocytes, monocyte-lymphocyte ratio, neutrophil-lymphocyte ratio, and platelet-lymphocyte ratio). CRP was lower in the metformin group but was not statistically significant. Adipokines were dysregulated overall but were not different between the two groups. Serum IFN-γ, IL-8, TNF-α, and CXCL1 trended lower in the metformin group but did not reach significance. These results suggest that metformin improves CV risk biomarkers and insulin resistance in patients with HS. When the results of this study are considered alongside other studies in HS and related conditions, it is likely that metformin also has beneficial effects on metabolic markers and systemic inflammation in HS (CRP, serum adipokines, and immune mediators), warranting further research.

Keratinocytes and immune cells in the epidermis are key drivers of inflammation in hidradenitis suppurativa providing a rationale for novel topical therapies

BACKGROUND

Hidradenitis suppurativa (HS) is a debilitating inflammatory skin disease characterized by painful nodules, drainage and scarring in skin folds. Injectable adalimumab is the only drug approved by the US Food and Drug Administration for the treatment of HS. Although systemic Janus kinase (JAK) inhibitors show promise, serious side-effects have been reported. There are no highly effective topical treatments for HS; furthermore, the contribution of epidermal keratinocytes to the intense inflammation has largely been unexplored.

OBJECTIVES

We investigated the role of keratinocytes and epidermal immune cells in HS inflammation at all Hurley stages of disease severity. We aimed to determine whether ruxolitinib can mitigate inflammation from keratinocytes and to develop a better understanding of how topical therapeutics might benefit patients with HS.

METHODS

We used skin samples from 87 patients with HS (Hurley stages I-III) and 39 healthy controls to compare keratinocyte- and immune cell-driven epidermal inflammation, in addition to the response of lesional HS keratinocytes to treatment with interferon (IFN)-γ and ruxolitinib. We used haematoxylin and eosin staining, immunohistochemistry, immunoblotting and quantitative reverse-transcription polymerase chain reaction assessments in whole skin, isolated epidermis, and cultured keratinocytes from healthy controls and both nonlesional and lesional HS skin to identify and define epidermal and keratinocyte-mediated inflammation in HS and how this may be targeted by therapeutics.

RESULTS

HS lesional keratinocytes autonomously secreted high levels of chemokines, such as CCL2, CCL3 and CXCL3, which recruited neutrophils, CD8 T cells, and natural killer cells to the epidermis. Keratinocytes were the dominant source of tumour necrosis factor-α and interleukin (IL)-6 in HS lesions with little to no contribution from underlying dermal immune cells. In the presence of IFN-γ, which is dependent on immune cell infiltrate in vivo, keratinocytes expressed increased levels of additional cytokines including IL-1β, IL-12, IL-23 and IL-36γ. The JAK inhibitor ruxolitinib mitigated the expression of inflammatory cytokines and chemokines in HS lesional keratinocytes, thus providing a rationale for future study as a topical treatment for HS.

CONCLUSIONS

This study demonstrates that keratinocytes actively recruit immune cells to HS epidermis and interactions between these cells drive a broad inflammatory profile in HS epidermis. Targeting epidermal inflammation in HS with novel topical formulations may be highly efficacious with reduced systemic side-effects.

Bone Metabolism in Patients with Hidradenitis Suppurativa: A Case-control Study

Hidradenitis suppurativa (HS) is a chronic inflammatory disease of the hair follicles. The aim of this case-control study was to assess whether HS is associated with disturbances in trabecular bone score, bone mineral density, bone remodelling markers, and calciotropic hormones. A total of 81 patients and 79 controls of similar age and sex were included. Demographic, anthropometric, laboratory data, trabecular bone score, bone mineral density, serum 25-hydroxyvitamin D (25OHD), serum amino-terminal pro-peptide of type 1 collagen (PINP), and C-terminal telopeptide of type 1 collagen (CTX) concentrations were assessed in both groups. Patients with HS had lower serum 25OHD levels than controls, and approximately 62% of them had vitamin D deficiency. Serum PINP was increased and CTX was decreased in patients with HS. Fully adjusted trabecular bone score values were lower in patients with HS compared with controls. Adjusted lumbar bone mineral density was similar in HS and controls, whilst total hip bone mineral density was lower in patients with HS. There were no statistical differences regarding disease severity in terms of 25OHD, serum turnover markers, bone mineral density, or trabecular bone score values. This study shows that patients with HS have lower trabecular bone score and total hip bone mineral density values than population-based controls. In addition, the prevalence of vitamin D deficiency is high in subjects with HS.

Case Report: Comorbid Hyper-IgD Syndrome and Hidradenitis Suppurativa - A New Syndromic Form of HS? A Report of Two Cases

Hidradenitis Suppurativa (HS) is a chronic suppurative disease of the pilosebaceous unit. The current model of HS pathophysiology describes the condition as the product of hyperkeratinisation and inflammation at the hair follicular unit. Environmental factors (such as smoking and obesity), gender, genetic predisposition, and skin dysbiosis are considered the main pathogenic drivers of the disease. Autoinflammatory syndromes associated with HS are rare but may help to highlight the potential roles of autoinflammation and dysregulated innate immune system in HS. Therefore, it is of major relevance to increase the awareness about these diseases in order to improve the understanding of the disease and to optimize the management of the patients. Herein, we report for the first time, to our knowledge, two clinical cases of Hyper-IgD syndrome-associated HS. Hyper-IgD is an autoinflammatory syndrome caused by a mevalonate kinase deficiency (MKD), a key kinase in the sterol and isoprenoid production pathway. We describe the potentially shared pathophysiological mechanisms underpinning comorbid MKD-HS and propose therapeutic options for the management of these patients.

Ex Vivo Culture Models of Hidradenitis Suppurativa for Defining Molecular Pathogenesis and Treatment Efficacy of Novel Drugs

Hidradenitis suppurativa (HS) is a complex and debilitating inflammatory skin disease for which no effective treatment is available currently. This is partly because of the lack of adequate human or animal models for defining the pathobiology of the disease. Here, we describe the development of air-liquid (A-L) interface, liquid-submersion (L-S), and bioreactor (Bio) ex vivo skin culture models. All three ex vivo platforms were effective for culturing skin samples for up to 14 days. Tissue architecture and integrity remained intact for at least 3 days for healthy skin and 14 days for HS skin. Up to day 3, no significant differences were observed in % early apoptotic cells among all three platforms. However, late apoptotic/necrotic cell death was increased in HS skin at day 3 in A-L and Bio culture. These cultures efficiently support the growth of various cells populations, including keratinocytes and immune cells. Profiling inflammatory gene signatures in HS skin from these ex vivo cultures showed dynamic changes in expression at day 3 and day 14. All three culture platforms were necessary to represent the inflammatory gene status of HS skin at day 0, suggesting that not all gene clusters were identically altered in each culture method. Similarly, cytokine/chemokine profiling of the supernatants from vehicle- and drug-treated ex vivo HS cultures again showed a better prediction of drug efficacy against HS. Overall, development of these three culture systems collectively provides a powerful tool to uncover the pathobiology of HS progression and screen various drugs against HS.

Janus kinase 1 inhibitor INCB054707 for patients with moderate-to-severe hidradenitis suppurativa: results from two phase 2 studies

Background

Janus kinase (JAK)‐mediated cytokine signalling contributes to local and systemic inflammation in hidradenitis suppurativa (HS).

Objectives

To describe the safety and efficacy results from two multicentre phase II trials of the JAK1 inhibitor INCB054707 in patients with moderate‐to‐severe HS.

Methods

Patients received open‐label INCB054707 15 mg once daily (QD; Study 1) or were randomized to INCB054707 30, 60 or 90 mg QD or placebo (3 : 1 within each cohort; Study 2) for 8 weeks. Eligible patients were aged 18–75 years and had moderate‐to‐severe HS (Hurley stage II/III disease), lesions present in at least two anatomical locations, and a total abscess and inflammatory nodule count ≥ 3. The primary endpoint for both studies was safety and tolerability. Secondary endpoints included HS Clinical Response (HiSCR) and other efficacy measures.

Results

Ten patients were enrolled in Study 1 (15 mg INCB054707) and 35 in Study 2 (INCB054707: 30 mg, n = 9; 60 mg, n = 9; 90 mg, n = 8; placebo, n = 9). Overall, 70% of patients in Study 1 and 81% of patients receiving INCB054707 in Study 2 experienced at least one treatment‐emergent adverse event; 30% and 42% of patients, respectively, had at least one treatment‐related adverse event. Among the evaluable patients, three (43%) in Study 1 and 17 (65% overall: 30 mg, 56%; 60 mg, 56%; 90 mg, 88%) receiving INCB054707 vs. 4 patients (57%) receiving placebo in Study 2 achieved HiSCR at week 8.

Conclusions

INCB054707 was well tolerated, with responses observed in patients with moderate‐to‐severe HS. The safety and efficacy findings from these studies demonstrate proof of concept for JAK1 inhibition in HS. The studies are registered on ClinicalTrials.gov (NCT03569371 and NCT03607487).

Clinical considerations in the management of hidradenitis suppurativa in women

Hidradenitis suppurativa (HS) is a chronic, inflammatory disease of the skin with a predilection for women. The role of sex hormones, including estrogen and progesterone, is incompletely understood, but alterations in hormone levels may play a role in disease activity for many patients. Specific clinical considerations should be made for women with HS, particularly in the setting of pregnancy, childbirth, breastfeeding, and menopause. Current knowledge gaps regarding HS include the cumulative impact of disease across an individual's lifespan, as well as the mechanistic role of sex hormones in the disease. An improved understanding of the pathophysiologic role of hormones in HS would optimize our ability to use targeted therapies for hormonally driven disease. Psychological and psychosexual support for women with HS is an important facet of any holistic management strategy for the disease. This article integrates up-to-date pathogenic and mechanistic insights with evidence-based clinical management to optimize care for women with HS.

Increased Serum Levels of S100A4 and S100A15 in Individuals Suffering from Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease. Recently, some S100 proteins have been suggested to play an important role in the pathogenesis of chronic immune-mediated inflammatory diseases and they may constitute valuable biomarkers for these diseases’ diagnosis and monitoring. The objective of the current study was to investigate, for the first time, serum levels of S100A4 and S100A15 in individuals suffering from HS. Furthermore, we assessed the associations between S100A4 and S100A15 serum levels and the severity of disease, CRP serum concentration and some demographic and clinical data. Serum levels of S100A4 and S100A15 were evaluated with the commercially available ELISA kit according to the manufacturer’s instructions. The serum level of S100A4 in individuals with HS was significantly elevated as compared to controls, with the highest level found in the individuals in Hurley stage II. The S100A15 serum level was positively correlated with the CRP concentration and was associated with the severity of the disease. The serum level of S100A15 in the individuals in Hurley stage III was significantly elevated compared to that of the controls and the individuals with HS in Hurley stages I and II. S100A4 and S100A15 may be considered as new serum biomarkers for the monitoring of HS progression, and they may play a role in the pathogenesis of HS by promoting inflammatory process and fibrosis.

Metabolic syndrome and hidradenitis suppurativa: epidemiological, molecular, and therapeutic aspects

Hidradenitis suppurativa (HS) is a chronic, suppurative condition of the pilosebaceous unit. Patients suffering from HS demonstrate a molecular profile in keeping with a state of systemic inflammation and are often found to fit the criteria for a diagnosis of metabolic syndrome (MetS). In this paper, we review the literature with regards to established data on the prevalence of MetS in HS patients and revise the odds ratio of comorbid disease. Furthermore, we attempt to draw parallels between inflammatory pathways in HS and MetS and evaluate how convergences may explain the risk of comorbid disease, necessitating the need for multidisciplinary care.

Hidradenitis suppurativa: A folliculotropic disease of innate immune barrier dysfunction?

The innate immune system of human skin consists of a multi-layered barrier consisting of cells and soluble effector molecules charged with maintaining homeostasis and responding to insults and infections. It has become increasingly clear that these barrier layers become compromised in skin diseases, especially in disorders of an (auto)inflammatory nature. In the case of hidradenitis suppurativa, great strides have been made in recent years in characterizing the underlying breakdown in homeostatic innate immunity, including an increasing understanding of the central role of the hair follicle in this process. This breakdown appears to occur at multiple levels: the pilosebaceous unit, associated epithelium, the cutaneous microbiome, alteration of immune cell function and local molecular events such as complement activation. This review seeks to summarize, contextualize and analyse critically our current understanding of how these innate immune barriers become dysregulated in the early stage(s) of hidradenitis suppurativa, and to speculate on where potential hidradenitis suppurativa research could be most fruitful.

Efficacy and Safety of Bimekizumab in Moderate to Severe Hidradenitis Suppurativa: A Phase 2, Double-blind, Placebo-Controlled Randomized Clinical Trial

Question

What is the efficacy and safety of bimekizumab in individuals with moderate to severe hidradenitis suppurativa (HS)?

Findings

In this double-blind, placebo-controlled, phase 2 randomized clinical trial including 90 randomized patients with HS (73 completed the trial), bimekizumab demonstrated clinically meaningful and consistent improvements in participants with HS vs placebo across all assessed outcome measures. Serious adverse events occurred in 2 of 46 bimekizumab-treated participants (4%) and 2 of 21 placebo-treated participants (10%).

Meaning

These initial clinical efficacy and safety data suggest that dual inhibition of interleukin 17A and 17F by bimekizumab may be a viable treatment approach for HS, with the potential to achieve deep responses in clinical outcome measures, and support further evaluation.

Importance

Hidradenitis suppurativa (HS) is a chronic inflammatory disease with a high burden for patients and limited existing therapeutic options.

Objective

To evaluate the efficacy and safety of bimekizumab, a monoclonal IgG1 antibody that selectively inhibits interleukin 17A and 17F in individuals with moderate to severe HS.

Design, Setting, and Participants

This phase 2, double-blind, placebo-controlled randomized clinical trial with an active reference arm was performed from September 22, 2017, to February 21, 2019. The study included a 2- to 4-week screening period, a 12-week treatment period, and a 20-week safety follow-up. Of 167 participants screened at multiple centers, 90 were enrolled. Eligible participants were 18 to 70 years of age with a diagnosis of moderate to severe HS 12 months or more before baseline.

Interventions

Participants with HS were randomized 2:1:1 to receive bimekizumab (640 mg at week 0, 320 mg every 2 weeks), placebo, or reference arm adalimumab (160 mg at week 0, 80 mg at week 2, and 40 mg every week for weeks 4-10).

Main Outcomes and Measures

The prespecified primary efficacy variable was the proportion of participants with a 50% or greater reduction from baseline in the total abscess and inflammatory nodule count with no increase in abscess or draining fistula count (Hidradenitis Suppurativa Clinical Response [HiSCR] at week 12. Exploratory variables included proportion achieving a modified HiSCR with 75% reduction of HiSCR criteria (HiSCR₇₅) or a modified HiSCR with 90% reduction of HiSCR criteria (HiSCR₉₀), change in Patient’s Global Assessment of Pain, and Dermatology Life Quality Index total scores.

Results

Eighty-eight participants received at least 1 dose of study medication (61 [69%] female; median age, 36 years; range, 18-69 years). Seventy-three participants completed the study, including safety follow-up. Bimekizumab demonstrated a higher HiSCR rate vs placebo at week 12 (57.3% vs 26.1%; posterior probability of superiority equaled 0.998, calculated using bayesian analysis). Bimekizumab demonstrated greater clinical improvements compared with placebo. Improvements in the International Hidradenitis Suppurativa Severity Score (IHS4) were seen at week 12 with bimekizumab (mean [SD] IHS4, 16.0 [18.0]) compared with placebo (mean [SD] IHS4, 40.2 [32.6]). More bimekizumab-treated participants achieved positive results on stringent outcome measures compared with placebo. At week 12, 46% of bimekizumab-treated participants achieved HiSCR₇₅ and 32% achieved HiSCR₉₀, whereas 10% of placebo-treated participants achieved HiSCR₇₅ and none achieved HiSCR₉₀; in adalimumab-treated participants, 35% achieved HiSCR₇₅ and 15% achieved HiSCR₉₀. One participant withdrew because of adverse events. Serious adverse events occurred in 2 of 46 bimekizumab-treated participants (4%), 2 of 21 placebo-treated participants (10%), and 1 of 21 adalimumab-treated participants (5%).

Conclusions and Relevance

In this phase 2 randomized clinical trial, bimekizumab demonstrated clinically meaningful improvements across all outcome measures, including stringent outcomes. Bimekizumab’s safety profile was consistent with studies of other indications, supporting further evaluation in participants with HS.

Trial Registration

ClinicalTrials.gov Identifier: NCT03248531

Epithelialized tunnels are a source of inflammation in hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic, painful, and burdensome inflammatory disease manifesting in nodules and abscesses, with progression to chronically draining tunnels in later-stage disease.

OBJECTIVE

We sought to determine whether HS tunnels are immunologically active participants in disease activity.

METHODS

Skin biopsy specimens were obtained by using ultrasound guidance in untreated patients with HS and those enrolled in an open-label study of brodalumab (ClinicalTrials.gov identifier NCT03960268) for patients with moderate-to-severe HS.

RESULTS

Immunohistochemistry of HS biopsy specimens demonstrated that the epithelialized HS tunnels recapitulate the psoriasiform epidermal hyperplasia morphology of the overlying epidermis, displaying molecular inflammation, including S100A7 (psoriasin) positivity, as well as features of epidermal skin, including loricrin, filaggrin, lipocalin-2, and Melan-A positive cells. Tunnels were associated with increased infiltration of T cells, dendritic cells, and neutrophils; formation of neutrophil extracellular traps, and increased expression of psoriasiform proinflammatory cytokines. Unsupervised hierarchical clustering demonstrated a separation of HS samples based on the presence or absence of tunnels. Tunnels isolated by microdissection had higher levels of epithelium-derived inflammatory cytokines compared with the overlying epidermis and healthy controls. Clinically, the size and draining of the tunnels were decreased with treatment with the IL-17RA antagonist brodalumab.

CONCLUSION

These data suggest that tunnels are a source of inflammation in HS.

Ultrasound-guided de-roofing of epithelialised tunnels of hidradenitis suppurativa

Hidradenitis Suppurativa is a chronic inflammatory disease manifesting in painful nodules, abscesses and malodorous draining tunnels with a pre-disposition to flexural regions of skin. Traditional surgical interventions include excision of clinically visible lesions and in severe cases - excision down to fascia of entire anatomical regions (axilla, groin) and repair with split-thickness grafting or skin substitutes. However, such techniques are plagued by long healing times (up to several months), extensive tissue loss and high recurrence rates given that a large proportion of disease is not clinically visible. Deroofing is a tissue-saving surgical technique, ideal for Hurley Stage 2 disease, which when combined with bedside pre-operative sonography can allow for the accurate identification and removal of occult dermal tunnels whilst minimising the risks of pain, infection, minimising healing times and can be safely conducted in the setting of immunomodulatory therapy.

Yin and Yang: A disrupted skin microbiome and an aberrant host immune response in hidradenitis suppurativa

The skin microbiome plays an important role in maintaining skin homeostasis by controlling inflammation, providing immune education and maintaining host defense. However, in many inflammatory skin disorders the skin microbiome is disrupted. This dysbiotic community may contribute to disease initiation or exacerbation through the induction of aberrant immune responses in the absence of infection. Hidradenitis suppurativa (HS) is a complex, multifaceted disease involving the skin, innate and adaptive immunity, microbiota and environmental stimuli. Herein, we discuss the current state of HS skin microbiome research and how microbiome components may activate pattern recognition receptor (PRR) pathways, metabolite sensing pathways and antigenic receptors to drive antimicrobial peptide, cytokine, miRNA and adaptive immune cell responses in HS. We highlight the major open questions that remain to be addressed and how antibiotic therapies for HS likely influence both microbial burden and inflammation. Ultimately, we hypothesize that the two-way communication between the skin microbiome and host immune response in HS skin generates a chronic positive feed-forward loop that perpetuates chronic inflammation, tissue destruction and disease exacerbation.

Long-standing refractory hidradenitis suppurativa responded to a brodalumab monotherapy in a patient with psoriasis: A possible involvement of Th17 across the spectrum of both diseases

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic inflammatory skin disease mainly affecting apocrine gland-rich areas of the body with painful nodules, persisted abscess, sinus tracts, and scarring. The etiopathology of HS remains unclearly understood, but the disease is considered as a polygenic autoinflammation condition originating from follicular hyperkeratosis and occlusion. Recent advances concerning the substantial roles of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-17, and IL-23 have accelerated in developing a repertoire of therapeutic biologics in HS. Currently five biologics antagonistic for these different cytokines, adalimumab, anakinra, etanercept, infliximab, and ustekinumab, have been explored in the treatment setting of HS; however, only limited evidence is available for the therapeutic advantage of IL-17 pathway blockade. We present a 47-year-old Japanese man who had a long-standing, debilitating HS complicated with psoriasis, both of which were refractory to a series of the standard treatment. Not only psoriatic skin but also HS lesions responded dramatically to brodalumab, an IL-17 receptor antagonist, accompanied with decrease of validated assessments, namely the Hurley's staging classification and modified Sartorius score. Brodalumab was well tolerated with rapid improvement and no adverse reaction, and finally gave a satisfactory maintenance of disease remission. To our best knowledge, this is the first successful use of anti-IL-17 receptor antibody in a Japanese case with coexistence of HS and psoriasis. We also discuss extending understanding of the potential benefit and current limitation of brodalumab in the treatment of HS.

Association of Birth Weight, Childhood Body Mass Index, and Height With Risk of Hidradenitis Suppurativa

Importance

There is a lack of evidence on the association of birth weight, childhood body mass index (BMI), change in BMI during childhood, and childhood height with subsequent risks of hidradenitis suppurativa (HS) in adulthood.

Objective

To investigate the association of birth weight, childhood BMI, change in BMI during childhood, and childhood height with subsequent risks of HS in adulthood in a large Danish population-based cohort.

Design, Setting, and Participants

This cohort study included 347 200 schoolchildren from the Copenhagen School Health Records Register born from 1930 to 1996 who were linked to the Danish National Patient Register of hospital discharge diagnoses to identify cases of HS. Birth weight was reported by parents or guardians, whereas childhood weight and height were measured by school physicians or nurses at ages 7 through 13 years. Cox proportional hazards regressions were used to estimate hazard ratios (HRs) and 95% CIs. Statistical analysis was performed from February 20, 2019, to May 15, 2019.

Main Outcomes and Measures

A diagnosis of HS as recorded in the Danish National Patient Register.

Results

Among the 347 200 children included in the study (175 750 boys) during the follow-up period from 1977 to 2017, 1037 individuals (677 females; median age at diagnosis, 39 years [range, 15-73 years]) received a diagnosis of HS. A nonlinear (U-shaped) association was found between birth weight and HS, such that both the lightest (2.00-2.75 kg; HR, 1.36 [95% CI, 1.10-1.68]) and the heaviest babies (4.26-5.50 kg; HR, 1.39 [95% CI, 1.01-1.93]) had increased risks of HS compared with normal-weight babies (3.26-3.75 kg; P = .04 for deviation from linearity). The risk of HS increased significantly with increasing BMI z score at each age from 7 to 13 years, from an HR of 1.32 (95% CI, 1.24-1.40) per BMI z score at 7 years of age to an HR of 1.50 (95% CI, 1.40-1.61) per BMI z score at 13 years of age. Compared with children with a normal weight at 7 and 13 years of age, those with a normal weight at 7 years of age and overweight at 13 years of age had a significantly increased risk of HS (HR, 2.11 [95% CI, 1.63-2.74]) and children with persistent overweight at both ages also had an increased risk of HS (HR, 2.61 [95% CI, 2.02-3.38]). Children with overweight at 7 years of age but with normal weight at 13 years of age did not have a significantly increased risk of HS (HR, 1.05 [95% CI, 0.67-1.67]). Childhood height at all ages was not associated with risk of HS (children at 7 years had an HR of 1.00 [95% CI, 0.94-1.07], and those 13 years had an HR of 1.06 [95% CI, 0.99-1.13], per z score).

Conclusions and Relevance

This cohort study found that both the lightest and heaviest babies had increased risks of HS. Childhood BMI was positively and significantly associated with risk of HS development in adulthood. These findings suggest that returning to normal weight before puberty reduces risks of HS to levels observed in children who were never overweight. Childhood height was not associated with risk of HS.

The Microbiome in Hidradenitis Suppurativa: A Review

INTRODUCTION

Hidradenitis suppurativa (HS) is a chronic autoinflammatory skin disease. It is characterised by the development of abscesses and nodules in intertriginous anatomical sites. Whilst it is now recognised as an autoinflammatory condition rather than an infective disease, bacteria are implicated in disease pathogenesis.

METHODS

We performed a search of the literature from inception to 12 August 2020 using the search terms "hidradenitis suppurativa", "Verneuil's disease", "acne inversa", "microbiome", "bacteriology" and "microbiology". Studies were included if they assessed the cutaneous, gut or oral bacteria, bacteriology or microbiome in hidradenitis suppurativa.

RESULTS

Twenty-one studies examining the cutaneous microbiome and two studies examining the gastrointestinal microbiome in HS were identified. No studies examining the oral microbiome in HS were identified. A total of 972 patients and 46 healthy controls were included across studies examining the cutaneous microbiome. A total of 100 patients and 36 controls were included across both gut microbiome studies. Coagulase-negative Staphylococcus, anaerobes such as Porphyromonas and Prevotella, and Staphylococcus aureus species were commonly encountered organisms across the included cutaneous microbiome studies. The studies examining the gut microbiome were limited, with one small study demonstrating an alteration in the gut microbiome composition compared to controls. The other study found no alteration to the gut microbiome in patients with HS compared to those with inflammatory bowel disease (IBD) and HS, and IBD and/or psoriasis.

CONCLUSION

Research should be undertaken into the oral microbiome in HS. Further research should be undertaken examining the cutaneous and gut microbiome in HS, and its relationship with documented co-morbidities. Additionally, metagenomics-focused studies may help identify the relationship between microorganisms and host, and this may shed light on new pathways of disease pathogenesis. This may help identify potential future therapeutic targets.

A Systematic Review of Promising Therapeutic Targets in Hidradenitis Suppurativa: A Critical Evaluation of Mechanistic and Clinical Relevance

This systematic review identifies and critically evaluates the mechanistic and clinical evidence of new promising therapeutic targets in hidradenitis suppurativa (HS). Evidence for these targets is largely based on observational data with limited ex vivo and translational data from clinical trials. A number of placebo-controlled studies have been completed or are underway utilizing IL-1, IL-23, IL-17, complement, and Jak inhibition, although there is concern regarding elevated placebo response rates and the questionable validity of clinical scores in some participant subsets. Knowledge gaps are identified suggesting a direction for future mechanistic studies in HS, including more comprehensive inflammatory endotype profiling of disease.

Histologic progression of acne inversa/hidradenitis suppurativa: Implications for future investigations and therapeutic intervention

Since first recognized in 1839, the pathogenesis of acne inversa (AI) has undergone repeated revisions. Although there is agreement that AI involves occlusion of hair follicles with subsequent inflammation and the formation of tracts, the histologic progression of this disease still requires refinement. The objective of this study was to examine the histologic progression of AI based on the examination of a large cohort of punch biopsies and excisional samples that were examined first by hematoxylin and eosin staining. The most informative of these samples were step‐sectioned and stained by immunohistochemistry for epithelial and inflammatory markers. Based on this examination, the following observations were made: 1) AI arises from the epithelium of the infundibulum of terminal and vellus hairs; 2) These form cysts and epithelial tendrils that extend into soft tissue; 3) Immunohistochemical staining demonstrates the epithelium of AI is disordered with infundibular and isthmic differentiation and de novo expression of stem cell markers; 4) The inflammatory response in AI is heterogeneous and largely due to cyst rupture. The conclusions of this investigation were that AI is an epithelial‐driven disease caused by infiltrative, cyst forming tendrils and most of the inflammation is due to cyst rupture and release of cornified debris and bacteria. Cyst rupture often occurs below the depths of punch biopsy samples indicating their use for analysis may give an incomplete picture of the disease. Finally, our data suggest that unless therapies inhibit tendril development, it is unlikely they will cause prolonged treatment‐induced remission in AI.

Cytokine Pathways and Investigational Target Therapies in Hidradenitis Suppurativa

Background: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease affecting areas with a high density of apocrine glands and characterized by subcutaneous nodules that may evolve into fistulas with pus secretion. Methods: The aim of this review is to investigate all current knowledge on cytokine regulation in the pathogenesis of HS. A systematic literature research using the words “cytokine”, “interleukin”, “pathway”, and “hidradenitis suppurativa” was performed in PubMed/Medline and Scopus/Embase databases. A search of the clinicaltrials.gov website for interventional recruiting and completed trials including the term “hidradenitis suppurativa” was also performed up to August 2020. We will discuss the pathogenetic role of various cytokines in HS and potential therapeutic targets for this debilitating disease. Results: The pathophysiology underlying this complex condition has not been clearly defined. An upregulation of various cytokines, such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-1, IL-17, IL-23, and other molecules seems to be related to this inflammatory condition. Various cells, such as lymphocytes T Helper 1 and 17 and keratinocytes seem to be involved in the genesis of this condition. Conclusions: Several future studies and clinical trials are necessary in order to have new knowledge about HS and to properly treat this complex condition.

A systematic review and critical appraisal of metagenomic and culture studies in hidradenitis suppurativa

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic inflammatory skin disease with still largely unknown pathogenesis. While infectious organisms have been identified in lesions of the disease since the 1980s, questions remain over the role that bacteria and microbiome play. Recent studies using 16S ribosomal RNA gene sequencing and larger culture-based studies have begun to paint a clearer picture of the microbial world of HS. With this systematic review, we summarize all the work that has been done to date in HS bacteriology, analyse potential pitfalls and limitations of the current studies, and address future directions of investigation. This systematic review attempted to collate and analyse all bacteriology studies done to date. This review was prospectively registered with PROSPERO (1670769) performed in line with the PRISMA checklist. Twenty two studies were identified comprising 862 individual HS patients for culture studies and 206 HS patients for 16S rRNA gene sequencing studies. Methodology tended to be varied, with different sampling, culturing and sequencing methods as well as amount of analysis and stratification of patients. Bacteria identified as elevated in HS lesions in sequencing studies as well as grown from HS lesions in culture studies are identified and discussed. These primarily included the anerobic Gram-negative bacilli Prevotella, Porphyromonas and Fusibacterium, the Gram-positive bacilli Corynebacterium, and the Gram-positive cocci Staphylococcus, Streptococcus and Parvimonas. Potential interactions, as well as work in other disease models with related bacteria are also discussed. Areas of further investigation include in vitro studies of interactions between bacteria and keratinocytes, gut and oral microbiome studies and deep sequencing studies for virulence and phage factors.

Hidradenitis suppurativa is an autoinflammatory keratinization disease: A review of the clinical, histologic, and molecular evidence

The pathogenic model of hidradenitis suppurativa is in the midst of a paradigm shift away from a disorder of primary follicular occlusion to an autoinflammatory keratinization disease. Observational, experimental, and therapeutic evidence supports the concept of hidradenitis suppurativa as a primarily inflammatory disorder, a disorder of autoimmunity, or both, in contrast to the current prevailing paradigm of primary follicular occlusion. The lack of reliable and high-fidelity disease models has limited the available experimental and mechanistic evidence to support or refute one pathogenic model over another. This scholarly review synthesizes the existing clinical, histologic, and molecular data to evaluate the extant evidence supporting the autoinflammatory paradigm and further informing the molecular mechanisms of hidradenitis suppurativa pathogenesis. Follicular hyperkeratosis/occlusion and perifollicular inflammation coexist in histologic specimens, with interleukin 1α demonstrated to stimulate comedogenesis in the infundibulum. pH elevation in occluded body sites alters the microbiome and amplifies existing T-helper cell type 17 immunoresponses. Known metabolic comorbidities and smoking are known to upregulate interleukin 1α in follicular keratinocytes. Identified genetic variants may alter epidermal growth factor receptor signaling, leading to upregulated keratinocyte inflammatory responses. The process of follicular rupture and dermal tunnel formation can be explained as secondary responses to inflammatory activation of fibroblasts and epithelial-mesenchymal transition, with antibody production associated with inflammatory amplification in advanced disease. This review aims to reevaluate and integrate the current clinical, histologic, and molecular data into a pathogenic model of hidradenitis suppurativa. This is essential to advance our understanding of the disease and identify novel therapeutic targets and approaches.

Risk of connective tissue disease, morphoea and systemic vasculitis in patients with hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) has been associated with auto-inflammatory conditions, yet the risk of developing connective tissue disease (CTD), morphoea and systemic vasculitis has not been well-characterized.

OBJECTIVES

We sought to evaluate the risk of developing CTD, morphoea and systemic vasculitis in patients with HS.

METHODS

Using claims data, we identified patients with HS and used 2 : 1 risk-set sampling to identify patients without HS. Patients with existing CTD were excluded. Patient follow-up lasted until first occurrence of the following events: the occurrence of outcome (i.e. systemic lupus erythematosus, morphoea, systemic sclerosis, Sjogren's Syndrome and systemic vasculitis), death, disenrolment or end of data stream. Hazard ratios (HR) of developing CTD, morphoea and systemic vasculitis were computed after 1 : 1 propensity score (PS) matching.

RESULTS

After 2 : 1 risk-set sampling, we identified 78 122 HS patients and 156 247 non-HS comparators. The mean follow-up was 540 days. After PS matching, HS patients had an increased risk of systemic lupus erythematosus HR = 1.63 (1.31-2.03) and morphoea HR = 2.02 (1.32-3.11), compared to non-HS patients. We did not observe an increased risk for systemic sclerosis HR = 0.90 (0.59-1.44), Sjogren's Syndrome HR = 0.91 (0.73-1.14) or systemic vasculitis HR = 0.87 (0.64-1.20).

CONCLUSION

In this population-based study, we observed an increased risk of developing systemic lupus erythematous and morphoea subsequent to a first-recorded diagnosis of hidradenitis suppurativa.

Medical and Surgical Management of Hidradenitis Suppurativa: A Review of International Treatment Guidelines and Implementation in General Dermatology Practice

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic painful skin disease that severely impairs patients' quality of life. While high-quality trials of HS therapies remain limited, medical knowledge of best treatment practices is rapidly evolving, leading to the recent publication of multiple international treatment guidelines for HS.

SUMMARY

This review compares international HS treatment guidelines, describes evidence for effectiveness of common and emerging HS therapies, and provides guidance for integrating evidence-based HS care into practice. Although over 50 medical and procedural treatments are mentioned across international HS guidelines, only adalimumab and infliximab have grade B/weak recommendation or higher across all major guidelines. This review describes the appropriate patient selection and effectiveness of the most commonly used medical and procedural treatments for HS. It also includes recommendations for counseling, dosing, and duration of medical therapies as well as procedure videos for the practicing dermatologist.

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.

Beyond antibodies: B cells in Hidradenitis Suppurativa: Bystanders, contributors or therapeutic targets?

Hidradenitis Suppurativa (HS) is a chronic inflammatory dermatosis in which B cells play a prominent but unclear role. Our understanding of the role of B cells in innate and adaptive immunity (including antibody production, antigen presentation and effector functions) is rapidly evolving; and these novel findings require integration into the pathophysiologic model of HS. B cells are transiently present in normal human skin and have functions in the maintenance of innate cutaneous immunity. Recruitment and trafficking of B cells in significant numbers to skin is mediated via B cell-specific chemokines as well as shared signalling with T-cells. The evidence suggests that the presence of antibody-secreting B cells is not sufficient to induce clinical disease and T-cell interaction is required to induce clinical disease. Such interactions can occur in secondary lymphoid organs adjacent to involved tissue or in tertiary lymphoid organs which develop in response to the HS inflammatory milieu. This milieu directly mediates the types of antibodies produced by B cells, given the role of cytokines in B-cell class switching. Identified antibodies in HS (IgG, IgM, ASCA, ACPA) currently demonstrate no evidence of pathogenicity, but may be novel biomarkers for disease severity. B cells also have anti-inflammatory properties through production of IL-10 and IL-35 which require experimental validation. Overall, B cells in HS are likely to be involved in amplification of a pre-existing inflammatory response; but it remains unclear whether they may be directly pathogenic.

Biologic therapies for the treatment of hidradenitis suppurativa

Introduction: Hidradenitis suppurativa (HS) is a chronic skin disorder characterized by inflammatory nodules, abscesses, and fistulae. Patients tend to present in young adulthood and are predominantly female. The pathogenesis of HS involves apopilosebaceous gland follicle occlusion and affected areas often occur where this type of gland predominates. Treatment selection depends on HS severity, which is included in different scoring systems. In recent years, biological therapies have been evaluated and used with increasing frequency in moderate-to-severe HS disease.Areas covered: This review focuses on biological therapies for HS as assessed in case reports, case series, and clinical trials. The efficacy, hidradenitis suppurativa scoring systems, and long-term results of these therapies are discussed depending on the studies' endpoints.Expert opinion: Adalimumab is currently the only FDA-approved HS biological therapy. Some patients do not experience treatment efficacy with adalimumab at 40 mg/week, which may result in increasing the dose or seeking other treatments. Infliximab is the next line of HS treatment with demonstrated efficacy. Other biological therapies being studied have demonstrated efficacy in small patient groups, but lack study power. Further studies may provide answers to seeking treatment options for patients who fail to improve on current standard HS treatment.

Hidradenitis Suppurativa: Current Understanding of Pathogenic Mechanisms and Suggestion for Treatment Algorithm

Hidradenitis suppurativa is one of the most distressing dermatological conditions and has a significant negative impact on patients' quality of life. However, the exact pathogenic mechanisms remain incompletely understood and-therefore-efficient therapies are still lacking. The current manuscript focuses on new findings on its pathogenic mechanisms and aims to provide practical therapy recommendations.

Role of the Complement Pathway in Inflammatory Skin Diseases: A Focus on Hidradenitis Suppurativa

Although the role of immune dysregulation in hidradenitis suppurativa (HS) has yet to be elucidated, recent studies identified several complement abnormalities in patients with HS. The complement system serves a critical role in the modulation of immune response and regulation of cutaneous commensal bacteria. Complement is implicated in several inflammatory skin diseases including systemic lupus erythematosus, angioedema, pemphigus, bullous pemphigoid, and HS. A model of HS pathogenesis is proposed, integrating the role of commensal bacteria, cutaneous immune responses, and complement dysregulation. The role of complement in disease pathogenesis has led to the development of novel anticomplement agents and clinical trials investigating the efficacy of such treatments in HS.

Case report: Treating a co-existence of hidradenitis suppurativa and psoriasis with different therapeutic approaches

Hidradenitis suppurativa and psoriasis are considered chronic inflammatory diseases suggesting the existence of common pathogenetic pathways. We present two cases of comorbid psoriasis and hidradenitis suppurativa, treated with certolizumab pegol and brodalumab due to failure of response to other conventional therapies. Monoclonal antibody therapies have revolutionized the treatment of chronic inflammatory disorders such as psoriasis and hidradenitis suppurativa. Given the good clinical response to anti-IL-17 and anti-tumor necrosis factor agents in patients undergoing psoriasis and hidradenitis treatment, investigations on this direction could represent the starting point in new therapeutic approach for revolutionary treatment in these difficult-to-treat diseases.

Contribution of fibroblasts to tunnel formation and inflammation in hidradenitis suppurativa/ acne inversa

The precise pathogenic mechanisms in the development, persistence and worsening of hidradenitis suppurativa (HS) remain ill-defined. This chronic inflammatory dermatosis displays a strong Th1 and Th17 inflammatory signature with elevated levels of TNF-α, IL-1β, IL-17 and IFNγ in lesional and perilesional tissue. HS significantly differs to other chronic inflammatory dermatoses due to the development of hypertrophic scarring and dermal tunnels. The development of scarring and tunnels suggests that fibroblastic stromal cells (including myofibroblasts, fibroblasts, pericytes etc) may be involved in the development and progression of disease. Heterogeneous populations of fibroblasts have been identified in other inflammatory disorders and malignancy which contribute to inflammation and present novel therapeutic targets for fibrotic disorders. Findings in HS are consistent with these fibroblast subpopulations and may contribute to tunnel formation, aggressive squamous cell carcinoma and the phenotypic presentation of familial HS variants. We describe the existing knowledge regarding these mechanistic pathways and methods to confirm their involvement in the pathogenesis of HS.

The contradictory inefficacy of methotrexate in hidradenitis suppurativa: a need to revise pathogenesis or acknowledge disease heterogeneity?

The pathogenesis of hidradenitis suppurativa (HS) centers around Th17/Treg dysfunction illustrated by lesional elevation of IL-17A, IL-6, and other inflammatory mediators resulting in a chronic feed-forward inflammatory cascade. Similar inflammatory mechanisms have been identified in psoriasis and rheumatoid arthritis (RA) in which traditional immunosuppressants (including methotrexate) are routinely used with reasonable levels of disease control. Methotrexate's mechanism of action in these instances includes downregulation of the Th17 axis via alterations in dendritic cell and T-cell activity and maturation. Published data suggest methotrexate in an ineffective therapy in HS, which does not pair with our current understanding of the mechanisms of disease. The reasons behind this, including are discussed. Some HS patients may benefit from drugs such as methotrexate, and acknowledgment of the potential of disease heterogeneity will allow exploration of which factors may enable identification of such individuals.

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.

A systematic review and critical evaluation of inflammatory cytokine associations in hidradenitis suppurativa

Background: The pathogenesis of hidradenitis suppurativa (HS) remains unclear. In order to develop effective treatment strategies, a deeper understanding of pathophysiology is needed. This is impaired by multiple small studies with inconsistent methodologies and the impact of co-occurring pro-inflammatory conditions such as smoking and obesity.

Methods: This systematic review aimed to collate all published reports of cytokine studies in tissue, blood, serum and exudate. It was registered with PROSPERO (Registration number CRD42018104664) performed in line with the PRISMA checklist.

Results: 19 studies were identified comprising 564 individual HS patients and 198 control patients examining 81 discrete cytokines. Methodology was highly varied and the quality of studies was generally low. There was a large degree of variance between the measured levels of cytokines. 78.2% of cytokines demonstrated heterogeneity by the chi-squared test for homogeneity and hence meta-analysis was not deemed appropriate. However, a strong and significant IL-17 signalling component was identified.

Conclusions: Cytokines consistently elevated in lesional, peri-lesional and unaffected tissue are identified and discussed. Areas for further investigation include the role of dendritic cells in HS; the contribution of obesity, smoking, diabetes and the microbiome to cytokine profiles in HS; and examining the natural history of this disease through longitudinal measurements of cytokines over time.