Myeloid marker S100A8/A9 and lymphocyte marker, soluble interleukin 2 receptor: biomarkers of hidradenitis suppurativa disease activity?

Antimicrobial Peptide Signaling in Skin Diseases

Antimicrobial peptides (AMPs) are important innate immune molecules at microbe-host interfaces. The biophysical properties of AMPs that facilitate direct killing of microbes have been extensively reviewed. In this article, we focus on how AMPs perform immunomodulatory functions through interaction with host receptors on epithelial, immune, and neuronal cell types. We summarize the current knowledge of known AMPs in the skin, the receptors that respond to AMPs, and the downstream intracellular signaling pathways. In the end, we discuss the roles of AMP signaling systems in skin diseases.

Demographic Data, Risk Factors, and Disease Burden of HS Patients in Lithuania at a Reference Center

BACKGROUND

Hidradenitis suppurativa (HS) diagnosis often faces a global delay of 7.2 years due to factors like lack of recognition, stigma, and socioeconomic barriers. Limited effective therapies and frequent exacerbations impact patients' quality of life, posing a significant burden on healthcare systems.

METHODS

HS patients were assessed according to European Hidradenitis Suppurativa Foundation (EHSF) Registry questionnaire guidelines at various stages of the disease and treatment.

RESULTS

The study included 49 patients; 57.14% (n = 28) of them were male. The average age of the subjects was 39.91 ± 13.665 years; the average BMI was 27.84 ± 7.362. A total of 59.18% (n = 29) were active or previous smokers. There were statistically more male smokers than female (p < 0.01). Average disease onset was 25.71 ± 13.743 years; the mean time to diagnosis was 5.2 ± 7.607 years. A total of 70.2% (n = 33) were previously misdiagnosed. Subjects had 6.17 ± 6.98 painful days over the preceding 4 weeks. The average intensity of pain according to the visual analogue scale (VAS) was 5.60 ± 3.36 points. The mean dermatology life quality index (DLQI) at baseline was 8.9 ± 7.436.

CONCLUSIONS

The research revealed delayed diagnoses, especially for females. Smoking was linked to higher Hurley stages, with a prevalence among male smokers, and HS had a substantial impact on patients' quality of life.

Hidradenitis suppurativa: new insights into disease mechanisms and an evolving treatment landscape

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic disabling and debilitating inflammatory disease with a high unmet medical need. The prevalence of HS reported in most studies is 1-2%, although it is likely to be under-reported and estimates vary globally owing to variance in data collection methods, ethnicity, geographical location and under-diagnosis. HS is characterized by persistent, painful cutaneous nodules, abscesses and draining tunnels commonly affecting the axillary, anogenital, inguinal and perianal/gluteal areas. Over time, chronic uncontrolled inflammation results in irreversible tissue destruction and scarring. Although the pathophysiology of HS has not been fully elucidated, the tumour necrosis factor (TNF)-α and interleukin (IL)-17 pathways have an important role, involving multiple cytokines. Currently, treatment options include topical medications; systemic therapies, including repeated and/or rotational courses of systemic antibiotics, retinoids and hormonal therapies; and various surgical procedures. The anti-TNF-α antibody adalimumab is currently the only biologic approved by both the US Food and Drug Administration and the European Medicines Agency for HS; however, its efficacy varies, with a clinical response reported in approximately 50% of patients in phase III trials. HS is a rapidly evolving field of discovery, with a diverse range of agents with distinct mechanisms of action currently being explored in clinical trials. Several other promising therapeutic targets have recently emerged, and agents targeting the IL-17 and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways are the most advanced in ongoing or completed phase III clinical trials. Alongside limited therapeutic options, significant challenges remain in terms of diagnosis and disease management, with a need for better treatment outcomes. Other unmet needs include significant diagnostic delays, thus missing the therapeutic 'window of opportunity'; the lack of standardized outcome measures in clinical trials; and the lack of established, well-defined disease phenotypes and biomarkers.

Aberrant expression of interleukin-17A in mast cells contributes to the pathogenesis of hidradenitis suppurativa

BACKGROUND

Hidradenitis suppurativa (HS) significantly diminishes the quality of life for patients. Delayed diagnosis represents a significant challenge in effectively managing HS.

OBJECTIVES

To identify and characterize the key mediator in HS.

METHODS

Bioinformatic transcriptomic analysis was applied to identify potential candidates contributing to the disease process of HS. Skin samples from 40 patients with HS, four with psoriasis and 29 with normal skin were included. The expression of interleukin (IL)-17A was evaluated and compared among samples of normal skin, psoriatic skin and skin from different stages of HS by immunohistochemistry or dual-colour immunofluorescence. In vitro experiments and RNA sequencing analysis were also conducted to validate the expression of IL-17A and its pathogenic effect in HS.

RESULTS

Transcriptomic database analyses identified IL-17 signalling as a potential contributor to HS. In HS, the predominant IL-17A+ cell population was identified as mast cells. IL-17A+ mast-cell density was significantly elevated in HS, especially in samples with advanced Hurley stages, compared with normal skin and psoriasis samples. The close contact between IL-17A+ mast cells and IL-17 receptor A (IL-17RA)-expressing keratinocytes was demonstrated, along with the significant effects of IL-17A on keratinocyte cell proliferation and HS pathogenic gene expression. Treatment with biologics (brodalumab or adalimumab) reduced the severity of the disease and the number of IL-17A+ mast cells in affected tissues.

CONCLUSIONS

The presence of high-density IL-17A+ mast cells may serve as a valuable pathological marker for diagnosing HS. Moreover, developing therapeutic drugs targeting IL-17A+ mast cells may provide a new approach to treating HS.

New Insight into the Molecular Pathomechanism and Immunomodulatory Treatments of Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is an immune-mediated inflammatory disorder characterized by deep-seated nodules, abscesses, sinus tracts and scars localized in the intertriginous areas. It is accompanied by pain, malodourous secretion and a dramatically decreased quality of life. Although the pathogenesis has not been entirely elucidated, the primary event is follicular hyperkeratosis of the pilosebaceous apocrine unit. Since the registration of the tumor necrosis factor-alpha inhibitor Adalimumab in 2015, several cytokines have been implicated in the pathomechanism of HS and the research of novel therapeutic targets has been intensified. We provide an update on the inflammatory cytokines with a central role in HS pathogenesis and the most promising target molecules of future HS management.

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

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

Innate immunity and microbial dysbiosis in hidradenitis suppurativa - vicious cycle of chronic inflammation

Hidradenitis Suppurativa (HS) is a chronic multifactorial inflammatory skin disease with incompletely understood mechanisms of disease pathology. HS is characterized by aberrant activation of the innate immune system, resulting in activation of pathways that aim to protect against pathogenic microorganisms, and also contribute to failure to resolve inflammation. Imbalance in innate immunity is evident in deregulation of host antimicrobial peptides (AMPs) and the complement system associated with the microbiome dysbiosis. The pathology is further complicated by ability of pathogens associated with HS to overcome host immune response. Potential roles of major AMPs, cathelicidin, defensins, dermcidin, S100 proteins, RNAse 7 and complement proteins are discussed. Dysregulated expression pattern of innate immunity components in conjunction with bacterial component of the disease warrants consideration of novel treatment approaches targeting both host immunity and pathogenic microbiome in HS.

Hidradenitis Suppurativa and Comorbid Disorder Biomarkers, Druggable Genes, New Drugs and Drug Repurposing-A Molecular Meta-Analysis

Chronic inflammation and dysregulated epithelial differentiation, especially of hair follicle keratinocytes, have been suggested as the major pathogenetic pathways of hidradenitis suppurativa/acne inversa (HS). On the other hand, obesity and metabolic syndrome have additionally been considered as an important risk factor. With adalimumab, a drug has already been approved and numerous other compounds are in advanced-stage clinical studies. A systematic review was conducted to detect and corroborate HS pathogenetic mechanisms at the molecular level and identify HS molecular markers. The obtained data were used to confirm studied and off-label administered drugs and to identify additional compounds for drug repurposing. A robust, strongly associated group of HS biomarkers was detected. The triad of HS pathogenesis, namely upregulated inflammation, altered epithelial differentiation and dysregulated metabolism/hormone signaling was confirmed, the molecular association of HS with certain comorbid disorders, such as inflammatory bowel disease, arthritis, type I diabetes mellitus and lipids/atherosclerosis/adipogenesis was verified and common biomarkers were identified. The molecular suitability of compounds in clinical studies was confirmed and 31 potential HS repurposing drugs, among them 10 drugs already launched for other disorders, were detected. This systematic review provides evidence for the importance of molecular studies to advance the knowledge regarding pathogenesis, future treatment and biomarker-supported clinical course follow-up in 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.

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.

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.

Potential predictive biomarkers of adalimumab response in patients with hidradenitis suppurativa

BACKGROUND

Adalimumab provides significant efficacy for patients with hidradenitis suppurativa (HS), which was demonstrated by at least 50% of patients achieving a clinical response by week 12 that was maintained through to week 168 in the PIONEER trials.

OBJECTIVES

To identify whether there are biomarkers that could predict adalimumab response, as well as markers that differentially respond to adalimumab in patients with HS.

METHODS

Baseline and week-12 plasma samples from the PIONEER studies were used to assess the levels of circulating proteins by multiplex and enzyme-linked immunosorbent assays.

RESULTS

Analyses revealed significantly higher high-sensitivity C-reactive protein (hs-CRP) and chemokine (C-C motif) ligand (CCL) 16 (HCC-4) levels in nonresponders at baseline and identified a multivariate response signature of calprotectin, fractalkine and HCC-4, reaching an 86% predictive accuracy rate for adalimumab response. Additionally, post-treatment reduction of plasma C-X-C motif chemokine ligand (CXCL)9, CXCL8 (interleukin-8) and CCL19 (macrophage inflammatory protein 3β) were greater in adalimumab super-responders than in nonresponders (P = 0·026, P = 0·044 and P = 0·026, respectively). These cytokines are involved in the recruitment of innate and adaptive inflammatory cells, and/or stimulation of certain inflammatory responses, suggesting that these pathways could be disease drivers in adalimumab nonresponders.

CONCLUSIONS

These initial results suggest HCC-4, calprotectin and fractalkine could be potential predictive biomarkers of adalimumab response in HS and identified possible tumour necrosis factor-independent disease pathways.

The IL-23/IL-17 Pathway in Inflammatory Skin Diseases: From Bench to Bedside

Interleukin-17 (IL-17) is an essential proinflammatory cytokine, which is mainly secreted by the CD4+ helper T cells (Th17 cells) and subsets of innate lymphoid cells. IL-17A is associated with the pathogenesis of inflammatory diseases, including psoriasis, atopic dermatitis, hidradenitis suppurativa, alopecia areata, pityriasis rubra pilaris, pemphigus, and systemic sclerosis. Interleukin-23 (IL-23) plays a pivotal role in stimulating the production of IL-17 by activating the Th17 cells. The IL-23/IL-17 axis is an important pathway for targeted therapy for inflammatory diseases. Emerging evidence from clinical trials has shown that monoclonal antibodies against IL-23, IL-17, and tumor necrosis factor are effective in the treatment of patients with psoriasis, atopic dermatitis, hidradenitis suppurativa, pityriasis rubra pilaris, pemphigus, and systemic sclerosis. Here, we summarize the latest knowledge about the biology, signaling, and pathophysiological functions of the IL-23/IL-17 axis in inflammatory skin diseases. The currently available biologics targeting the axis is also discussed.

Calprotectin in acne vulgaris: A possible contributory role

BACKGROUND

Acne vulgaris (AV) is a common inflammatory skin disease involving dysfunction of the pilosebaceous unit. Many mechanisms for the pathogenesis of acne have been postulated; however, the precise pathogenesis is still uncertain.

AIM

Evaluation of the level of serum calprotectin in patients with AV and its correlation with the different clinical variables of the disease, particularly severity.

PATIENTS AND METHODS

This is a case-control study that included ninety subjects who were subdivided into two groups; group I, which included sixty patients complaining of AV with different grades of severity, and group II that included thirty apparent healthy age and sex-matched participants as a control group. Severity of AV was determined according to the Global Acne Grading System (GAGS). Serum calprotectin level was measured in both patients and controls by the enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

A highly statistically significant difference in the serum calprotectin level was found between patients with AV and control subjects. A highly significant positive correlation was found between the serum calprotectin levels and the severity of acne. Similarly, a significant positive correlation was found between serum calprotectin levels and the duration of the disease.

CONCLUSION

Serum calprotectin levels are increased in acne patients and are positively correlated with its severity.

Serum alarmin S100A8/S100A9 levels and its potential role as biomarker in myocarditis

Aims

The alarmin S100A8/S100A9 (S100A8/A9) is released by activated monocytes/macrophages and neutrophils in the setting lymphocytic myocarditis (MC). We recently demonstrated its therapeutic potential in experimental acute MC. Now, we investigated the diagnostic relevance of S100A8/A9 serum levels in patients with suspected acute and chronic MC and in patients with heart failure without cardiac inflammation.

Methods and Results

Serum S100A8/A9 levels were analysed in patients with a recent onset of MC [≤ 30 days, n = 32; ejection fraction (EF): 45.4 ± 12.9%], dilated cardiomyopathy patients with inflammation (n = 112; EF: 29.0 ± 11.4%), or without inflammation (n = 58; EF: 26.6 ± 9.3%), and controls (n = 25; EF: 68.5 ± 4.6%), by using specific ELISAs. Blood samples were collected at Time Point 1 (T1), where also endomyocardial biopsies (EMBs) were withdrawn. Patients with a recent onset of MC showed a 4.6‐fold increase in serum S100A8/A9 levels vs. controls (MC: 1948 ± 1670 ng/mL vs. controls: 426 ± 307 ng/mL; P < 0.0001). Serum S100A8/A9 correlated with the disease activity, represented by EMB‐derived counts of inflammatory cells (CD3: r = 0.486, P = 0.0047, lymphocyte function‐associated antigen‐1: r = 0.558, P = 0.0009, macrophage‐1 antigen: r = 0.434, P = 0.013), the EMB mRNA levels of S100A8, S100A9 (r = 0.541, P = 0.002), and left ventricular ejection fraction (LVEF: r = 0.498, P = 0.0043). EMB immunofluorescence co‐stainings display macrophages/monocytes and neutrophils as the main source of S100A8 and S100A9 in recent onset MC. The diagnostic value of serum alarmin levels (cut‐off 583 ng/mL) was characterized by a specificity of 92%, a sensitivity of 90.6%, positive predictive value of 93.5%, negative predictive value of 88.5%, and an accuracy of 0.949 (95% confidence interval [0.89–1]). In a subgroup of MC patients, S100A8/A9 serum levels and EMBs at T1 (n = 12) and a follow‐up visit (T2, n = 12, mean follow‐up 8.5 months) were available. A fall of serum S100A8/A9 (T1: 2208 ± 1843 ng/mL vs. T2: 888.8 ± 513.7 ng/mL; P = 0.00052) was associated with a reduced cardiac inflammation (CD3 T1: 70.02 ± 107.4 cells per square millimetre vs. T2: 59.18 ± 182.5 cells per square millimetre; P = 0.0342, lymphocyte function‐associated antigen‐1 T1: 133.5 ± 187.1 cells per square millimetre vs. T2: 74.12 ± 190.5 cells per square millimetre; P = 0.0186, and macrophage‐1 antigen T1: 132.6 ± 129.5 cells per square millimetre vs. T2: 54.41 ± 65.16 cells per square millimetre; P = 0.0015). Serum S100A8/A9 levels were only slightly increased in patients within the chronic phase of MC and in heart failure patients without inflammation vs. controls.

Conclusions

Serum S100A8/A9 might serve as an additional tool in the diagnostic workup of suspected acute MC patients.

Hidradenitis suppurativa

Hidradenitis suppurativa (HS; also designated as acne inversa) is a chronic inflammatory disorder, which affects the intertriginous skin and is associated with numerous systemic comorbidities. The estimated prevalence of HS is ~1% in most studied countries. Typically starting in early adulthood, cutaneous inflamed nodules, abscesses and pus-discharging tunnels develop in axillary, inguinal, gluteal and perianal body sites. The comorbidities of HS include metabolic and cardiovascular disorders, which contribute to reduced life expectancy. A genetic predisposition, smoking, obesity and hormonal factors are established aetiological factors for HS. Cutaneous changes seem to start around hair follicles and involve activation of cells of the innate and adaptive immune systems, with pivotal roles for pro-inflammatory cytokines such as tumour necrosis factor, IL-1β and IL-17. The unrestricted and chronic immune response eventually leads to severe pain, pus discharge, irreversible tissue destruction and scar development. HS has profound negative effects on patients' quality of life, which often culminate in social withdrawal, unemployment, depression and suicidal thoughts. The therapeutic options for HS comprise antibiotic treatment, neutralization of tumour necrosis factor and surgical intervention together with lifestyle modification. Nevertheless, there is an enormous need for awareness of HS, understanding of its pathogenesis and novel treatments.

Alterations in innate immunity and epithelial cell differentiation are the molecular pillars of hidradenitis suppurativa

BACKGROUND

The large unmet need of hidradenitis suppurativa/acne inversa (HS) therapy requires the elucidation of disease-driving mechanisms and tissue targeting.

OBJECTIVE

Robust characterization of the underlying HS mechanisms and detection of the involved skin compartments.

METHODS

Hidradenitis suppurativa/acne inversa molecular taxonomy and key signalling pathways were studied by whole transcriptome profiling. Dysregulated genes were detected by comparing lesional and non-lesional skin obtained from female HS patients and matched healthy controls using the Agilent array platform. The differential gene expression was confirmed by quantitative real-time PCR and targeted protein characterization via immunohistochemistry in another set of female patients. HS-involved skin compartments were also recognized by immunohistochemistry.

RESULTS

Alterations to key regulatory pathways involving glucocorticoid receptor, atherosclerosis, HIF1α and IL17A signalling as well as inhibition of matrix metalloproteases were detected. From a functional standpoint, cellular assembly, maintenance and movement, haematological system development and function, immune cell trafficking and antimicrobial response were key processes probably being affected in HS. Sixteen genes were found to characterize HS from a molecular standpoint (DEFB4, MMP1, GJB2, PI3, KRT16, MMP9, SERPINB4, SERPINB3, SPRR3, S100A8, S100A9, S100A12, S100A7A (15), KRT6A, TCN1, TMPRSS11D). Among the proteins strongly expressed in HS, calgranulin-A, calgranulin-B and serpin-B4 were detected in the hair root sheath, koebnerisin and connexin-32 in stratum granulosum, transcobalamin-1 in stratum spinosum/hair root sheath, small prolin-rich protein-3 in apocrine sweat gland ducts/sebaceous glands-ducts and matrix metallopeptidase-9 in resident monocytes.

CONCLUSION

Our findings highlight a panel of immune-related drivers in HS, which influence innate immunity and cell differentiation in follicular and epidermal keratinocytes as well as skin glands.

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.

North American clinical management guidelines for hidradenitis suppurativa: A publication from the United States and Canadian Hidradenitis Suppurativa Foundations: Part I: Diagnosis, evaluation, and the use of complementary and procedural management

Hidradenitis suppurativa is a chronic inflammatory disorder affecting hair follicles, with profoundly negative impact on patient quality of life. Evidence informing ideal evaluation and management of patients with hidradenitis suppurativa is still sparse in many areas, but it has grown substantially in the last decade. Part I of this evidence-based guideline is presented to support health care practitioners as they select optimal management strategies, including diagnostic testing, comorbidity screening, and both complementary and procedural treatment options. Recommendations and evidence grading based on the evidence available at the time of the review are provided.

Hidradenitis Suppurativa: Comprehensive Review of Predisposing Genetic Mutations and Changes

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disorder. A genetic component in the pathogenesis is highly likely considering that ~30% to 40% of patients with HS report a family history of the disease. The genetic mutations related to HS that have been reported to date suggest HS can be inherited as a monogenic trait because of a defect in either the Notch signaling pathway or inflammasome function, or as a polygenic disorder resulting from defects in genes regulating epidermal proliferation, ceramide production, or in immune system function. This review provides a summary of genetic mutations reported in patients diagnosed with HS and discusses the mechanisms by which these genes are involved in its pathogenesis.

Chitinase-3-like Protein 1 (YKL-40) Is Expressed in Lesional Skin in Hidradenitis Suppurativa

BACKGROUND/AIM

Hidradenitis suppurativa (HS) is a chronic disease. Recently, we suggested, chitinase-3-like protein 1 (YKL-40) as a new biomarker for HS since its serum levels were found to be elevated in patients. The objective of this study was to examine YKL-40 tissue expression in HS.

MATERIALS AND METHODS

The study was conducted on 7 patients with HS. The biopsies were obtained from lesional and non-lesional skin. The tissue expression of YKL-40 was assessed using an immunohistochemical method.

RESULTS

Inflammatory infiltrates of various grades were visible in all samples of lesional skin. The inflammatory cells within those infiltrates showed a strong cytoplasmic expression of YKL-40. In non-lesional HS skin the pattern of YKL-40 expression was similar to that observed in healthy skin.

CONCLUSION

Inflammatory infiltrates in HS skin lesions may be responsible for the elevated YKL-40 serum level. YKL-40 can be considered one of the most valuable biomarkers of HS.

Long-Wave Medical Infrared Thermography: A Clinical Biomarker of Inflammation in Hidradenitis Suppurativa/Acne Inversa

BACKGROUND

A more reliable classification of skin inflammation and severity of active disease results from ultrasound sonography and the new hidradenitis suppurativa/acne inversa (HS) classification system IHS4. However, an objective assessment of skin inflammation in a continuous mode is still the ultimate goal. Long-wave medical infrared thermography (MIT) may offer a blood flow and temperature differential assessment in inflammatory conditions.

OBJECTIVE

To evaluate the application of MIT in HS.

METHODS

Standardized photography of the areas involved or been candidates for HS involvement was performed and MIT pictures were taken simultaneously and superimposed on the photographs of 18 patients (11 female, 7 male, median age 38.75 years [95% confidence interval 28.5 and 51 years], Hurley score I 5.6%, Hurley score II 38.9%, and Hurley score III 55.5%). A modification of the Otsu's method facilitated the automatic lesion segmentation from the background, depicting the inflammation area. Moreover, MIT was administered in real-time mode during radical HS surgery.

RESULTS

A 1°C temperature difference from a corresponding symmetric body region was indicative of inflammation. MIT figures detected a gradual increase of skin temperature from 33.0°C in healthy skin on average to 35.0-36.6°C at the center of inflamma tory lesions in the axilla and to 35.4-36.9°C at the center of inflammation in the groin area. Real-time MIT assessment enabled the definition of the margins and depth of the surgical intervention during the procedure.

CONCLUSION

MIT is a promising tool for the detection of inflammation severity in HS lesions and can be used as a clinical biomarker in evaluation studies of medical and surgical HS treatment.

Apremilast for moderate hidradenitis suppurativa: no significant change in lesional skin inflammatory biomarkers

Background

Treatment with apremilast has recently demonstrated clinically meaningful improvement in moderate hidradenitis suppurativa (HS).

Objective

To evaluate the change in expression of inflammatory markers in lesional skin of HS patients receiving apremilast 30 mg twice daily (n = 15) for 16 weeks compared with placebo (n = 5).

Methods

At baseline, 5‐mm punch biopsies were obtained from an index lesion (HSL) and non‐lesional (HSN) skin in the same anatomical area. Subsequent HSL samples were taken as close as possible to the previously biopsied site at week 4 and week 16. After sampling, biopsies were split; one half was processed for in vivo mRNA analysis using real‐time quantitative PCR; the other half was cultured for ex vivo protein analysis using a proximity extension assay (Olink). Linear mixed effects models were calculated to compare the levels of inflammatory markers in HSL skin between apremilast and placebo over time.

Results

At baseline, 17 proteins with a fold change >2 in HSL vs. HSN skin were identified in 20 patients. The top five were IL‐17A (5), S100A12, CST5, IL‐12/23p40, CD6 (1) with fold changes ranging from 6.6 to 1638, respectively (FDR <0.044). Linear mixed effects models for 75 assays were calculated. Protein levels of S100A12 decreased during treatment in the apremilast group compared with the placebo group (p = 0.014, FDR = 0.186). None of the 14 genes exhibited significant changes in expression over time. However, an evident downward trend in relative mRNA expression of IL‐17A and IL‐17F was demonstrated in patients receiving apremilast.

Conclusion

We did not detect statistically significant changes in inflammatory markers in HSL skin of HS patients receiving apremilast compared with placebo, despite clinical improvement in the apremilast group. Nonetheless, S100A12 and IL‐17A were significantly elevated in HSL skin and showed a decrease in response to apremilast. The translational model in clinical trials involving HS clearly needs further improvement.

Increased interleukin (IL)-17 serum levels in patients with hidradenitis suppurativa: Implications for treatment with anti-IL-17 agents

BACKGROUND

Biologics seem to offer a promising nonsurgical approach in hidradenitis suppurativa (HS), especially in disease with highly pronounced inflammation. Recent studies revealed increased expression of a broad range of cytokines in lesional HS skin, including interleukin (IL)-17.

OBJECTIVE

This study was undertaken to determine IL-17 serum levels in this group of patients.

METHODS

Our study was conducted on a group of 86 patients between 16 and 72 years of age with HS. A total of 86 matched healthy volunteers constituted the control group. Enzyme-linked immunosorbent assay kits were used to quantify IL-17 serum concentration.

RESULTS

The mean IL-17 serum level of patients with HS was 3.68 ± 2.08 pg/mL, which was significantly elevated (P < .0001) compared with that found in healthy volunteers (2.5 ± 1.11 pg/mL). Moreover, there was a tendency toward higher serum concentrations of IL-17 in patients with more advanced disease (P = .005). Disease duration; patient sex, age, and body mass index; and smoking habits were not determining factors for IL-17 serum concentration.

LIMITATIONS

Hospital-based study population was a limitation, as was a lack of posttreatment assessment.

CONCLUSION

In light of our findings and literature on increased expression of IL-17 in HS lesions, evaluating the clinical effectiveness of using anti-IL-17 agents in the treatment of patients with HS is justified.

Diagnosing Hidradenitis Suppurativa

Three diagnostic criteria must be met for hidradenitis suppurativa: typical lesions, occurrence in one or more of the predilection areas, and that it is chronic and/or recurrent. Several outcome measures are used, including patient-reported pain and itch scales, Dermatology Life Quality Index, and Skindex. Hidradenitis suppurativa is associated with significant comorbidities that must be addressed in the evaluation of the patients.

Intrinsic Defect in Keratinocyte Function Leads to Inflammation in Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic, inflammatory, debilitating, follicular disease of the skin. Despite a high prevalence in the general population, the physiopathology of HS remains poorly understood. The use of antibiotics and immunosuppressive agents for therapy suggests a deregulated immune response to microflora. Using cellular and gene expression analyses, we found an increased number of infiltrating CD4(+) T cells secreting IL-17 and IFN-γ in perilesional and lesional skin of patients with HS. By contrast, IL-22-secreting CD4(+) T cells are not enriched in HS lesions contrasting with increased number of those cells in the blood of patients with HS. We showed that keratinocytes isolated from hair follicles of patients with HS secreted significantly more IL-1β, IP-10, and chemokine (C-C motif) ligand 5 (RANTES) either constitutively or on pattern recognition receptor stimulations. In addition, they displayed a distinct pattern of antimicrobial peptide production. These findings point out a functional defect of keratinocytes in HS leading to a balance prone to inflammatory responses. This is likely to favor a permissive environment for bacterial infections and chronic inflammation characterizing clinical outcomes in patients with HS.

Ustekinumab in hidradenitis suppurativa: clinical results and a search for potential biomarkers in serum

BACKGROUND

Treatment of hidradenitis suppurativa (HS) is difficult and the search for effective therapies continues.

OBJECTIVES

To evaluate the efficacy of ustekinumab and to discover a potential biomarker for HS.

METHODS

Seventeen patients were included in this open-label study and treated with 45 or 90 mg ustekinumab at weeks 0, 4, 16 and 28. Proteomic technology and enzyme-linked assay analysis was applied to sera.

RESULTS

Twelve patients completed the protocol. Moderate-to-marked improvement of the modified Sartorius score was achieved in 82% of patients at week 40 and the Hidradenitis Suppurativa Clinical Response 50 in 47%. With regard to the expression of 54 serum proteins, at baseline, a significant difference was observed between patients and healthy controls. Involved pathways were related to inflammation, immune cell signalling and tissue morphology/development. Good responders had milder disease and lower expression of leukotriene A4-hydrolase (LTA4H). Interleukin (IL)-2R, tumour necrosis factor-α, IL-17A and IL-17F were not elevated and did not change during treatment.

CONCLUSIONS

The majority of patients improved with ustekinumab. Although no biomarker was discovered, low LTA4H concentrations with mild disease severity may be predictive of the effectiveness of ustekinumab.

Keratinocytes and neutrophils are important sources of proinflammatory molecules in hidradenitis suppurativa

BACKGROUND

The pathogenesis of the chronic inflammatory skin disease hidradenitis suppurativa (HS, also known as acne inversa) involves epidermal alterations such as psoriasiform epidermal hyperplasia and keratin plugging. Keratinocytes are an important source of proinflammatory molecules in inflammatory skin diseases and can be stimulated by interleukin (IL)-17(+) cells.

OBJECTIVES

To explore the possible role of the epithelium in the pathogenesis of HS.

METHODS

We performed immunohistochemical stainings and Western blot experiments to investigate the localization and expression of inflammation-associated molecules, including the cytokine IL-17, components of the inflammasome including caspase-1, and the endogenous danger-associated molecular pattern molecules S100A8 and S100A9 (calprotectin). To examine a possible effect of upregulated proinflammatory cytokines on the inflammatory infiltrate, differences in the cellular composition of perifollicular and deep dermal infiltrates were analysed.

RESULTS

The number of IL-17(+) cells is increased in lesional and perilesional HS skin. The epidermis produces proinflammatory molecules and shows an upregulated expression of components of the NLRP3 inflammasome, activated caspase-1 and expression of S100A8/S100A9. Additionally, the course of the inflammatory process in HS involves influx of innate immune cells, particularly IL-17-expressing neutrophils.

CONCLUSIONS

IL-17-producing cells are present in lesional and perilesional HS skin and may contribute to the initiation of inflammatory processes. Furthermore, the epidermis is a source of proinflammatory cytokines, shows inflammasome activation and expresses S100A8/S100A9, thereby possibly contributing to the propagation of inflammation. A massive influx of IL-17-expressing neutrophils is observed in the deep infiltrate.

Correlation of inflammatory serum markers with disease severity in patients with hidradenitis suppurativa (HS)

BACKGROUND

Data regarding the association of routinely obtained serum markers of inflammation, namely C-reactive protein (CRP), white blood cell count, and neutrophil count, with disease severity of hidradenitis suppurativa (HS) according to a scoring system have not been reported to our knowledge.

OBJECTIVE

We sought to evaluate these inflammatory serum markers for assessing disease severity of HS.

METHODS

Medical files of 275 patients who were referred to the outpatient HS center of the Department of Dermatology, Venereology, and Allergology, Ruhr-University Bochum, in 2013 were evaluated retrospectively.

RESULTS

CRP levels and neutrophil count significantly differed among Hurley stages I, II and III (P < .0001, P = .0002, respectively). There were significant positive correlations among CRP levels (r = 0.496, P < .0001) and neutrophil count (r = 0.330, P = .0009) with modified Hidradenitis Suppurativa Score. CRP was a significant independent predictor for Hurley stage III (odds ratio 1.077, 95% confidence interval 1.013-1.145, P = .016). CRP and body mass index were significant independent predictors for severe disease according to modified Hidradenitis Suppurativa Score (odds ratio 1.065, 95% confidence interval 1.015-1.117, P = .009; and odds ratio 1.12, 95% confidence interval 1.009-1.243, P = .032, respectively).

LIMITATIONS

Files were analyzed retrospectively.

CONCLUSION

These inflammatory markers, especially CRP, are effective for assessing the extent of disease severity and the grade of inflammation in patients with HS.