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.

Antimicrobial peptides in hidradenitis suppurativa: a systematic review

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease of the hair follicle defined by recurrent nodules, tunnels and scarring involving the intertriginous regions. HS is associated with microbial dysbiosis and immune dysregulation. In HS, an increasing number of studies have investigated antimicrobial peptides (AMPs).

OBJECTIVES

To provide an overview of the literature on AMPs in HS, and to discuss the potential role of AMPs in the pathogenesis of HS.

METHODS

PubMed, Embase and the Cochrane Library were searched. The titles, abstracts and full texts of all articles were manually screened. Additionally, the reference lists of the included articles were screened and hand searched for relevant studies.

RESULTS

The final literature sample comprised 18 retrospective and prospective studies (no reviews or commentaries) published between 2009 and 2020.

CONCLUSIONS

This review demonstrates the multitude of AMPs in HS. Although the methodology of the studies varied, the included studies indicate a consistent overexpression of human β-defensin (hBD)-2, S100A7, S100A8 and S100A9 at both the mRNA and protein levels, and a decreased expression of hBD-1. Overall, the studies point to a dysregulation of AMPs in both lesional and nonlesional HS skin.

Quantifying the natural variation in lesion counts over time in untreated hidradenitis suppurativa: Implications for outcome measures and trial design

Background

Hidradenitis suppurativa (HS) demonstrates high placebo response rates in clinical trials, possibly due to the natural variability of the disease. No quantification of variability in lesion counts of untreated disease has been undertaken.

Objective

To quantify the variability of untreated HS.

Methods

Deidentified individual patient data from the placebo arms of PIONEER studies were analyzed, and measurements of within-subject coefficients of variation were examined. Variability was stratified by disease-associated variables (Hurley stage, BMI, sex, smoking, family history) and body site.

Results

Analysis of within-subject coefficients of variation demonstrated that half of the participants had a middle spread [difference between 75^th and 25^th percentiles of the subject's abscess and nodule counts] greater than 33% and 40% of their median abscess and nodule counts, and 25% of the subjects had a middle spread greater than 70% and 78% of their median abscess and nodule counts in PIONEER I and II, respectively. Hurley stage 2 participants had significantly greater within-subject variation than Hurley stage 3 patients. Variation was greater in the axillary and groin regions than in other anatomical locations.

Limitations

Limitations include the use of precollected clinical trial data.

Conclusion

The within-subject variability of the lesion counts in untreated HS was greater than previously appreciated. This has profound effects on outcome measures and the conduct of future clinical trials of HS.

Large-scale serum analysis identifies unique systemic biomarkers in psoriasis and hidradenitis suppurativa

BACKGROUND

Hidradenitis Suppurativa (HS) is now recognized as a systemic inflammatory disease, sharing molecular similarities with psoriasis. Direct comparison of the systemic inflammation in HS with psoriasis is lacking.

OBJECTIVES

To evaluate the serum proteome of HS and psoriasis, and to identify biomarkers associated with disease severity.

METHODS

In this cross-sectional study, 1,536 serum proteins were assessed using the Olink Explore (Proximity Extension Assay/PEA) high-throughput panel in moderate-to-severe HS (n=11), psoriasis (n=10) and age- and BMI-matched healthy controls (n=10).

RESULTS

HS displayed an overall greater dysregulation of circulating proteins, with 434 differentially expressed proteins (|FCH|≥1.2, p-value≤0.05) in HS versus controls, 138 in psoriasis versus controls, and 503 between HS and psoriasis. IL-17A levels and Th1/Th17 pathway enrichment were comparable between diseases, while HS presented greater TNF and IL-1β-related signaling. Th17-associated markers, PI3 and LCN2, were able to accurately differentiate psoriasis from HS. Both diseases presented increases of atherosclerosis-related proteins. Robust correlations between clinical severity scores and immune and atherosclerosis-related proteins were observed across both diseases.

CONCLUSIONS

HS and psoriasis share significant Th1/Th17 enrichment and upregulation of atherosclerosis-related proteins. Nevertheless, despite the greater body surface area involved in psoriasis, HS presents a greater serum inflammatory burden.

The Impact of Body Mass Index Upon the Efficacy of Adalimumab in Hidradenitis Suppurativa

Elevated BMI in Hidradenitis Suppurativa is associated with decreased response to Adalimumab therapy. BMI is proposed to segregate distinct disease subtypes. It remains unresolved whether a threshold BMI exists above which increased dosages may provide clinical benefit. Individual patient data from 578 PIONEER Phase 3 participants were analyzed. Descriptive, multivariable regression analysis and receiver operating characteristic (ROC) curves were calculated to assess the relationship between BMI and clinical outcome measures using R v3.5.3. Participants in the overweight and obese BMI category had reduced odds (58 and 67%, respectively) of achieving HiSCR [OR = 0.42 (95%CI −0.19, 0.91) p = 0.03], [OR = 0.33 (95%CI 0.16, 0.67) p = 0.002] compared to participants with BMI < 25. Reduction in AN count and IHS4 score was not significantly associated. ROC analysis did not reveal any cut off value predictive of treatment outcome. No correlation between BMI and baseline disease activity or covariate interactions were identified. These findings suggest BMI is a significant covariate in the setting of lower baseline disease activity, supporting the concept of disease heterogeneity and differential therapeutic response to Adalimumab.

Target molecules for future hidradenitis suppurativa treatment

The registration of the tumour necrosis factor-α inhibitor adalimumab in 2015 was a major step forward in the treatment of hidradenitis suppurativa/acne inversa (HS). However, it soon became evident that the effectiveness of adalimumab in daily practice was highly variable. A significant unmet medical need of HS patients remained, and the search for novel therapeutic targets was intensified. During the 10th European Hidradenitis Suppurativa Foundation (EHSF) e.V. Conference, reknown international HS investigators virtually presented and discussed the published data on these potential target molecules for future HS treatment. This article addresses the most promising molecules currently under investigation from a pathophysiological and clinical point of view. With phase III trials ongoing, the anti- interleukin (IL)-17 biologics bimekizumab and secukinumab are in the most advanced stage of clinical development showing promising results. In addition, targeting IL-1α with bermekimab has shown encouraging results in two clinical trials. Directing treatment at neutrophil recruitment and activation by targeting IL-36 with spesolimab fits well in the pathogenic concept of HS and clinical phase II trial results are pending. In contrast to in situ evidence, Complement 5a (C5a) and C5a receptor blockade have only shown greater clinical benefit in patients with severe HS. Inhibition of Janus kinase (JAK) 1 signalling in HS showed clinical efficacy only in the highest dosage, highlighting that careful surveillance of the balance between safety and efficacy of JAK inhibition is warranted. Overall, clinical efficacies of all novel treatments reported so far are modest. To guide drug development, more and better-defined translational data on the pathogenesis of this severe and enigmatic inflammatory skin disease are required.

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.

High inflammation in hidradenitis suppurativa extends to perilesional skin and can be subdivided by lipocalin-2 expression

BACKGROUND

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease presenting with diverse manifestations ranging from nodules and abscesses to draining tunnels. Whether the underlying inflammation from lesions extends to relatively healthy-appearing adjacent perilesional and distant nonlesional skin has not been systematically evaluated.

OBJECTIVE

We sought to characterize lesional, perilesional, and nonlesional skin in patients with HS.

METHODS

Skin biopsy samples were collected under ultrasound guidance from patients with active, untreated moderate-to-severe HS. Site-matched control biopsy samples from healthy volunteers were used for comparison.

RESULTS

RNA sequencing demonstrated that HS skin clustered separately from healthy control skin, with perilesional and lesion skin clustering together and away from nonlesional skin. Immunohistochemistry analysis identified psoriasiform hyperplasia with keratin 16 positivity in both perilesional and lesional skin, with comparable levels of CD3⁺, CD11c⁺, and neutrophil elastase-positive cellular infiltration. There was a marked upregulation of IL-17 signaling in perilesional and lesional skin. HS samples clustered on the basis of expression of lipocalin-2 (LCN2), with samples characterized by high LCN2 expression in the skin exhibiting a differing transcriptomic profile with significantly higher overall inflammation than that of skin characterized by low LCN2 levels.

CONCLUSIONS

Perilesional HS skin has a transcriptomic and molecular profile comparable to that of lesional skin. HS can be grouped into 2 distinct subtypes based on molecular levels of LCN2 in the skin, with the LCN2-high subtype exhibiting an overall higher inflammatory burden and an upregulation of targetable cytokines. To our knowledge, this is the first study to characterize a unique HS subtype (and a potential endotype) that may guide future therapeutic targets.

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.

Global Harmonization of Morphological Definitions in Hidradenitis Suppurativa for a Proposed Glossary

Importance

Standard morphological terminology and definitions are vital for identification of lesion types in the clinical trial setting and communication about the condition. For hidradenitis suppurativa (HS), morphological definitions have been proposed by different groups, representing various regions of the world, but no international consensus has been reached regarding such definitions. A lack of globally harmonized terminology and definitions may contribute to poor-quality data collection in clinical trials as well as poor communication among clinicians, investigators, and patients.

Objective

To establish and validate consensus definitions for typical morphological findings for HS lesions.

Methods

This study was conducted from August 2019 to August 2020. A Delphi study technique was used to assess agreement and then resolve disagreement on HS terminology among international experts. After an initial preparation phase, the process consisted of 3 rounds. In each round, participants reviewed preliminary definitions and rated them as "keep, with no changes," "keep, with changes," or "remove." Eight HS primary lesions, including papule, pustule, nodule, plaque, ulcer, abscess, comedo, and tunnel, were selected because they are most frequently used in HS clinician-reported outcome measures. The initial definitions were based on extant literature, and modifications were made between rounds based on qualitative thematic analysis of open-ended responses or discussion. Consensus was defined as greater than 70% to accept a definition. Consensus stability across rounds was defined as less than 15% change in agreement. Reliability was evaluated using the Gwet agreement coefficient. Validation was based on assessment of face validity and stability across rounds.

Results

A total of 31 experts participated. All 8 HS primary lesion definitions achieved greater than 70% consensus by Delphi round 3. Stability was achieved for papule, pustule, and abscess. The Gwet agreement coefficient increased from 0.49 (95% CI, 0.26-0.71) in round 1 to 0.78 (95% CI, 0.64-0.92) in round 3. Face validity was supported by expert endorsement to keep terms in survey responses. Previously unmeasured variation among clinicians' definition of tunnels was identified, and consensus was achieved.

Conclusions and Relevance

An international group of experts agreed on definitions for morphological features of HS lesions frequently included in HS clinical trials. These international consensus terms and definitions are needed to support consistency of lesion identification and quantification in clinical trials.

In-Depth Analysis of the Hidradenitis Suppurativa Serum Proteome Identifies Distinct Inflammatory Subtypes

Hidradenitis suppurativa is a chronic inflammatory dermatosis with presentations ranging from painful nodules and abscesses to draining tunnels. Using an unbiased proteomics approach, we assessed cardiovascular-, cardiometabolic-, and inflammation-related biomarkers in the serum of patients with moderate-to-severe hidradenitis suppurativa. The serum of patients with hidradenitis suppurativa clustered separately from that of healthy controls and had an upregulation of neutrophil-related markers (Cathepsin D, IL-17A, CXCL1). Patients with histologically diagnosed dermal tunnels had higher serum lipocalin-2 levels compared with those without tunnels. Consistent with this, patients with tunnels had a more neutrophilic-rich serum signature, marked by Cathepsin D, IL-17A, and IL-17D alterations. There was a significant serum‒skin correlation between proteins in the serum and the corresponding mRNA expression in skin biopsies, with healthy-appearing perilesional skin demonstrating a significant correlation with neutrophil-related proteins in the serum. CSF3 mRNA levels in lesional skin significantly correlated with neutrophil-related proteins in the serum, suggesting that CFS3 in the skin may be a driver of neutrophilic inflammation. Clinical significantly correlated with the levels of lipocalin-2 and IL-17A in the serum. Using an unbiased, large-scale proteomic approach, we demonstrate that hidradenitis suppurativa is a systemic neutrophilic dermatosis, with a specific molecular signature associated with the presence of dermal tunnels.

Ex Vivo Models and Interpretation of Mechanistic Studies in Hidradenitis Suppurativa

Current ex vivo and animal models of hidradenitis suppurativa (HS) display issues with fidelity and validity to human disease. Vossen et al.'s Transwell culture system holds potential to reliably assess mechanistic pathways in HS. Consideration of the sites of control tissue and comparison of the Transwell model against skin explant models would increase the validity of this method of inquiry.

Dermal tunnels influence time to clinical response and family history influences time to loss of clinical response in patients with hidradenitis suppurativa treated with adalimumab

BACKGROUND

Clinical response in hidradenitis suppurativa (HS) is most commonly assessed using the Hidradenitis Suppurativa Clinical Response (HiSCR) measure. Dermal tunnels, increased body mass index, smoking and antibiotic use significantly decrease the odds of achieving HiSCR. However, there are few data exploring if clinical features are also associated with length of time to achieve clinical response and/or time to lose clinical response.

AIM

To explore whether variables associated with achievement of HiSCR are associated with time to achieve HiSCR and time to loss of HiSCR in patients with HS treated with adalimumab 40 mg weekly in the PIONEER open-label extension study.

METHODS

Time-to-event analyses were performed to estimate time to achieve HiSCR and time to loss of HiSCR. The log rank test was used to compare cumulative incidence curves for a priori patient- and disease-associated factors. Cox regression analysis was performed to compare time-to-event outcomes in the presence of a priori variables. All statistical analyses were completed with R software (V3.5.3).

RESULTS

Presence of dermal tunnels significantly increased the time to achieve HiSCR (median 32.6 vs. 14.3 weeks, P = 0.02) and the hazard ratio (HR) was significant after controlling for patient and disease factors (HR = 0.70, 95% CI 0.51-0.96, P = 0.03). A positive family history of HS significantly decreased the time to loss of HiSCR (median 11.4 vs. 18 weeks, P < 0.001) and remained significant in Cox regression analysis (HR = 2.01, 95% CI 1.40-2.88, P < 0.001).

CONCLUSION

The presence of dermal tunnels significantly influences the odds of achieving HiSCR and the time to achieve HiSCR, while family history influences time to loss of HiSCR.

Doppler ultrasound-based noninvasive biomarkers in hidradenitis suppurativa: evaluation of analytical and clinical validity

BACKGROUND

There is a need for valid and reliable biomarkers in hidradenitis suppurativa (HS) for diagnosis and disease activity monitoring. Imaging-based biomarkers have the potential to fulfil this unmet need but no evaluation of analytical or clinical validity has yet been undertaken.

OBJECTIVES

To evaluate the analytical and clinical validity of sonographic epidermal thickness, Doppler ultrasound and dermal tunnel diameter in patients with HS.

METHODS

Twenty-two participants with HS were recruited and underwent a total of 65 matched ultrasound and skin biopsies of lesional, perilesional and unaffected tissue. Ultrasound measurements were performed in triplicate with mean values used. Skin biopsies underwent immunohistochemistry as per previously published methods. Analytical validity was assessed in individual ultrasound-biopsy pairs (n = 65) by comparisons of sonographic variables with histological correlates. Clinical validity was assessed in individual patients (n = 22) by comparing measures of overall disease activity with sonographic outcomes.

RESULTS

Epidermal thickness, dermal tunnel diameter and power Doppler intensity were assessed. Sonographic epidermal thickness and dermal tunnel diameter have high analytical validity with corresponding histological measurements. Power Doppler intensity demonstrated high correlation with dermal CD3⁺ and CD11c⁺ cell counts but not neutrophil elastase-positive cells. Power Doppler ultrasound has significant correlation with pain scores, abscess and nodule count, International HS Severity Scoring System score and number of draining tunnels.

CONCLUSIONS

Sonographic epidermal thickness and dermal tunnel diameter have acceptable levels of analytical validity in the assessment of HS lesions. Power Doppler intensity demonstrates acceptable clinical and analytical validity, suggesting it is a valid imaging-based biomarker in HS.

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.

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.

Clinical response rates, placebo response rates, and significantly associated covariates are dependent on choice of outcome measure in hidradenitis suppurativa: A post hoc analysis of PIONEER 1 and 2 individual patient data

BACKGROUND

The hidradenitis suppurativa clinical response (HiSCR) is the gold standard primary outcome measure for hidradenitis suppurativa clinical trials; however, it does not assess the presence of draining tunnels, a common finding in advanced disease. It is unclear what the effect of the presence or absence of draining tunnels has on the efficacy of adalimumab therapy in moderate and advanced disease.

OBJECTIVES

We evaluated the efficacy of adalimumab versus placebo using the International Hidradenitis Suppurativa Severity Scoring System (IHS4). Additionally, we assessed the effect of draining tunnels on therapeutic response as measured by both the HiSCR and change in nodule counts.

METHODS

Reanalysis was conducted with the IHS4 and PIONEER 1 and 2 individual patient data. Both binary outcomes (achieving HiSCR and achieving change in IHS4 severity category) and continuous outcomes (nodule counts and IHS4 score) were calculated with R. Regression modeling was undertaken to assess the effect of draining tunnels and other variables. P < .05 was considered statistically significant.

RESULTS

The significance of adalimumab therapy depended on the outcome measure used. Placebo response rates were highest when binary outcome measures were used. Draining tunnels, smoking, antibiotics, and body mass index influenced HiSCR response in PIONEER 2. Significant differences in disease severity were observed between PIONEER 1 and 2 data sets.

CONCLUSIONS

Elevated placebo response rates in PIONEER 1 and 2 are partially attributable to the use of binary outcome measures. Draining tunnels influence clinical response as measured by HiSCR and nodule counts in PIONEER 2. Further investigation into the effect of body mass index on clinical response is required.

Integrating complement into the molecular pathogenesis of Hidradenitis Suppurativa

Complement inhibition has been identified as a potential therapeutic target for multiple inflammatory disorders including Hidradenitis Suppurativa (HS). It is currently unclear how complement integrates into our current model of molecular pathogenesis in HS and whether it represents a central component of pathogenesis, or a neutrophil-associated bystander. Levels of C5a in serum and tissue correlate with disease activity and degree of neutrophilic infiltrates in HS. C5a has been associated with Th17 immune axis activation in psoriasis, rheumatoid arthritis and Crohn's disease with strong similarities to TH17 activation in HS. Porphyromonas species (which are identified in the HS microbiome) are able to cleave inactive C5 into C5a implicating the cutaneous microbiome as an activator of complement. C3a and C5a are associated with activation of the NLRP3 inflammasome, implicated in the inflammatory drive in HS. Complement receptors are present upon dendritic cells, monocytes, fibroblasts and adipocytes, which may broaden the potential contribution of complement to multiple aspects of HS pathogenesis. Dysregulation of complement receptor pathways has been documented in obesity, insulin resistance and polycystic ovarian syndrome leading to the possibility that complement may explain the epidemiological associations between these conditions and HS. The therapeutic potential of complement inhibitors in HS may be related to the therapeutic target (complement receptor or complement subunit) and the presence of alternate receptors (such as C5aR2) or ligands (including C3a, PAMPs and DAMPs). Integrating complement into the known pathogenesis of HS may aid in explaining the contradictory results between Phase 2 studies of C5a antagonists. It also allows for the identification of existing knowledge gaps to target further clinical investigation and research.

A Scoping Review of Non-invasive Imaging Modalities in Dermatological Disease: Potential Novel Biomarkers in Hidradenitis Suppurativa

Background: The development of imaging-based biomarkers has the potential to overcome major challenges in the accurate and reproducible assessment of disease severity and response to novel therapies in Hidradenitis Suppurativa (HS). Understanding the advantages and limitations of existing non-invasive imaging modalities in dermatological disease will aid in the development of hypotheses and inform the design of future studies. Methods: A scoping review was performed using Medline, Embase, Web of Science Databases and evaluation of "gray literature" until June 30, 2019. Citations were examined according to pre-defined inclusion and exclusion criteria. Citations were reviewed by two independent reviewers. Narrative Synthesis was used to summarize data, structured by imaging modality. Results: Non-invasive imaging modalities, such as ultrasound, MRI, RCM, EIS, OCT, and MIT, were identified. Only ultrasound, MRI and MIT have been used in HS. Image modalities vary in image depth, resolution, cost, accessibility and correlation with known aspects of disease activity in HS. Discussion and Conclusion: The benefits and limitations of each imaging modality are products of cost, accessibility, validity and reliability. An additional hurdle to the development of image-based biomarkers in HS is a lack of established analytical benchmarks that can be correlated with existing biological, inflammatory and clinical parameters. This review has identified potential imaging biomarkers, as well as relevant analytical benchmarks that reflect the presence or absence of disease. Further investigation work is needed to analytically and clinically validate these imaging variables in order to identify potential imaging biomarkers in HS.

In silico Analysis of Gamma-Secretase-Complex Mutations in Hidradenitis Suppurativa Demonstrates Disease-Specific Substrate Recognition and Cleavage Alterations

Background: Familial Hidradenitis Suppurativa and Familial Alzheimer's Disease are both associated with Gamma-Secretase Complex mutations; however, the two diseases are not epidemiologically associated. Understanding the molecular differences between the two diseases may aid in the development of hypotheses for differing pathogenesis and ultimately, targets for detection. Aims: To characterize the in silico structural and functional alterations to the Gamma Secretase Complex in documented mutations in Familial Hidradenitis Suppurativa, along with comparison of downstream substrate recognition and cleavage. Methods: In silico analysis of publicly available genomic data, assessment of protein structure and binding affinity using Swiss-model and Dynamut was undertaken. Differential Expression was expressed using Log Fold Change using the general framework for linear models in R. Differentially expressed genes (DEGs) were defined by FCH ≥1.5 or ≤-1.5 and false discovery rate (FDR ≤ 0.05). Results: Twenty three of 39 mutations in HS are degraded via nonsense mediated decay with altered substrate and binding affinity of substrates identified in the remaining mutations. Significant differential expression of ErbB4, SCNB1, and Tie1 in lesional skin was specific to Hidradenitis Suppurativa and EphB2, EPHB4, KCNE1, LRP6, MUSK, SDC3, Sortilin1 in blood specific to Familial Alzheimer's Disease. Discussion and Conclusions: We present the first in silico evidence as to the impact of documented mutations in Familial Hidradenitis Suppurativa. We also demonstrate unique substrate recognition and cleavage between Hidradenitis Suppurativa and Familial Alzheimer's Disease, providing a potential explanation as to why the two diseases do not occur within the same pedigree. These proteomic signatures may be a first step in identifying reliable biomarkers for Familial Hidradenitis Suppurativa.

Specimen Collection for Translational Studies in Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic inflammatory disorder characterized by painful nodules, sinus tracts, and scars occurring predominantly in intertriginous regions. The prevalence of HS is currently 0.053-4%, with a predominance in African-American women and has been linked to low socioeconomic status. The majority of the reported literature is  retrospective, population based, epidemiologic studies. In this regard, there is a need to establish a repository of biospecimens, which represent appropriate gender and racial demographics amongst HS patients. These efforts will diminish knowledge gaps in understanding the disease pathophysiology. Hence, we sought to outline a step-by-step protocol detailing how we established our HS biobank to facilitate the formation of other HS tissue banks. Equipping researchers with carefully detailed processes for collection of HS specimens would accelerate the accumulation of well-organized human biological material. Over time, the scientific community will have access to a broad range of HS tissue biospecimens, ultimately leading to more rigorous basic and translational research. Moreover, an improved understanding of the pathophysiology is necessary for the discovery of novel therapies for this debilitating disease. We aim to provide high impact translational research methodology for cutaneous biology research and foster multidisciplinary collaboration and advancement of our understanding of cutaneous 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.

A systematic review of reported cases of pachyonychia congenita tarda

Pachyonychia congenita (PC) describes a group of genodermatoses manifesting as thickened nails, palmoplantar keratoderma (PPK) and increased risk of cutaneous infections. PC tarda (PCT) describes late-onset PC, and associated genetic polymorphisms have been identified. There has been discussion that PCT may not be a distinct entity but rather misdiagnosed ectodermal dysplasia (ED) or PPK. Clarification of this is important for appropriate diagnosis, management and patient and genetic counselling. We aimed to conduct a systematic review of all reported cases of PCT in the published literature and collate evidence of genetic polymorphisms and clinical features to compare with known features of PC, ED and PPK. PubMed (1946 to 1 July 2018), Scopus (1955 to 1 July 2018) and Web of Science (1990 to 1 July 2018) databases were searched for case reports of PCT with no search restrictions on date or language. The search strategy included the terms pachyonychia congenita tarda OR pachyonychia congenita AND (late onset OR delayed OR PCT). In total, 13 reports describing 19 individual cases of PCT were identified. Of the three identified genetic polymorphisms, the earliest identified has been shown to be highly probably pathogenic, with the second likely to result in a benign amino acid change, while the third has since been shown to be nonpathogenic,. No epigenetic studies have been performed on any reported cases. Previous authors have suggested that a number of cases of PCT may be misdiagnosed ED or PPK. The findings of our review cannot refute this suggestion, and highlight the need for thorough clinical documentation of suspected cases of PCT and thorough genetic screening of kindred to identify causative genetic polymorphisms. Further high-quality datasets and reporting are needed to give further insight into the nature of PCT as a unique entity.

Inter-rater reliability of phenotypes and exploratory genotype-phenotype analysis in inherited hidradenitis suppurativa

BACKGROUND

Genotype-phenotype correlation measures the correlation between the presence of a physical trait with a group of similar mutations but is dependent on reliable phenotyping. It can provide information on disease pathogenesis, future disease progression, severity or activity. Such indicators would be valuable in hidradenitis suppurativa (HS).

OBJECTIVES

To assess inter-rater reliability (IRR) of HS clinical phenotypes and perform exploratory genotype-phenotype correlation in cases of HS with identified sequence variants.

METHODS

Linkage disequilibrium between variants was assessed. Genotype-phenotype correlations were explored using Spearman correlation coefficients. IRR was calculated using Cohen's κ. Correlation between phenotype classifications was assessed using the χ² statistic.

RESULTS

Forty-three sequence variants with clinical information were identified. Clinical phenotypes were classified as LC2 (n = 29; 67%), scarring folliculitis (n = 18; 42%), atypical (n = 38; 88%) and nodular (n = 26; 60%). LC1 phenotype was associated with regular (χ² = 41·289, P < 0·001) and typical (χ² = 29·013, P < 0·001) phenotypes. Cohen's κ was highest for van der Zee and Jemec (0·815), followed by Martorell-Calatayud et al. (0·813), Naasan and Affleck (0·774) and Canoui-Poitrine et al. (0·435) classifications. High linkage disequilibrium was seen between variants of Han Chinese pedigrees. No significant genotype-phenotype correlations were identified.

CONCLUSIONS

These findings may be influenced by selection, publication bias and the assumption that HS is a monogenic disorder. The poor IRR of existing phenotype measures suggests limited utility of existing measures. Further investigations into the correlation of clinical phenotypes with inflammatory biomarkers may aid in prognostic efforts for this disease. What's already known about this topic? Genotype-phenotype correlation can provide information regarding disease pathogenesis and predictions for future disease progression, severity or activity. The identification of such indicators in hidradenitis suppurativa (HS) would be valuable for patients and clinicians alike, given the lack of biomarkers or clinical predictors of disease. What does this study add? Sixty-five sequence variants across 20 separate genes were identified. There was no significant correlation between phenotype classification in four separate classification schema and gene, mutation type or impact on Notch signalling. Utility of current phenotype measurements are limited. The lack of genotype-phenotype correlation in HS is suggestive that the underlying assumption of inherited HS as a monogenic disorder may need revision.

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.

Proceeding report of the Second Symposium on Hidradenitis Suppurativa Advances (SHSA) 2017

The 2nd Annual Symposium on Hidradenitis Suppurativa Advances (SHSA) took place on 03-05 November 2017 in Detroit, Michigan, USA. This symposium was a joint meeting of the Hidradenitis Suppurativa Foundation (HSF Inc.) founded in the USA, and the Canadian Hidradenitis Suppurativa Foundation (CHSF). This was the second annual meeting of the SHSA with experts from different disciplines arriving from North America, Europe and Australia, in a joint aim to discuss most recent innovations, practical challenges and potential solutions to issues related in the management and care of Hidradenitis Suppurativa patients. The last session involved clinicians, patients and their families in an effort to educate them more about the disease.

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.