Mast cells are upregulated in hidradenitis suppurativa tissue, associated with epithelialized tunnels and normalized by spleen tyrosine kinase antagonism.

Mast cells have traditionally been associated with allergic inflammatory responses; however, they play important roles in cutaneous innate immunity and wound healing. The Hidradenitis Suppurativa tissue transcriptome is associated with alterations in innate immunity and wound healing-associated pathways; however, the role of mast cells in the disease is unexplored. We demonstrate that mast cell-associated gene expression (using whole tissue RNAseq) is upregulated, and in-silico cellular deconvolution identifies activated mast cells upregulated and resting mast cells downregulated in lesional tissue. Tryptase/Chymase positive mast cells (identified using IHC) localize adjacent to epithelialized tunnels, fibrotic regions of the dermis and at perivascular sites associated with Neutrophil Extracellular Trap formation and TNF-alpha production. Treatment with Spleen Tyrosine Kinase antagonist (Fostamatinib) reduces the expression of mast cell-associated gene transcripts, associated biochemical pathways and the number of tryptase/chymase positive mast cells in lesional hidradenitis suppurativa tissue. This data indicates that although mast cells are not the most abundant cell type in Hidradenitis Suppurativa tissue, the dysregulation of mast cells is paralleled with B cell/plasma cell inflammation, inflammatory epithelialized tunnels and epithelial budding. This provides an explanation as to the mixed inflammatory activation signature seen in HS, the correlation with dysregulated wound healing and potential pathways involved in the development of epithelialized tunnels.

Baseline clinical, hormonal and molecular markers associated with clinical response to IL-23 antagonism in hidradenitis suppurativa: A prospective cohort study.

Hidradenitis suppurativa is a complex inflammatory disease in which predicting therapeutic response remains challenging. IL-23 interacts with sex hormones but the relationships between the two in HS remains uninvestigated. To assess whether baseline clinical, hormonal or molecular markers are associated with clinical response to IL-23 antagonism with risankizumab in hidradenitis suppurativa. Twenty six individuals with Hurley stage 2/3 disease were administered risankizumab 150 mg Week 0, 4, 12. Baseline sex hormones and skin biopsies were taken. Clinical response at Week 16 assessed by the HiSCR, and differences between responders and non-responders assessed. Eighteen of 26 participants achieved HiSCR50 at week 16 (69.2%). Clinical response to IL-23 antagonism was associated with male gender, elevated total serum testosterone and decreased levels of FSH. Stratification by clinical responders/nonresponders identified differentially expressed genes including PLPP4 and MAPK10. Immunohistochemistry identified elevated numbers of CD11c, IL-17A and IL-17F positive cells compared to nonresponders. CD11c + cells significantly correlated with serum levels of total testosterone and inversely correlated with serum FSH. Clinical response to IL-23 antagonism in HS is associated with serum sex hormones, Th17 polarized inflammation in lesional tissue and CD11c + cells. These potential therapeutic biomarkers require further validation in larger cohorts but may suggest potential targeted HS therapy.

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 ß-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.

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, 1536 serum proteins were assessed using the Olink Explore (Proximity Extension Assay) high-throughput panel in patients with moderate-to-severe HS (n = 11), patients with psoriasis (n = 10) and age- and body mass index-matched healthy controls (n = 10). RESULTS: HS displayed an overall greater dysregulation of circulating proteins, with 434 differentially expressed proteins (absolute fold change ≥ 1·2; P ≤ 0·05) in patients with HS vs. controls, 138 in patients with psoriasis vs. controls and 503 between patients with HS and patients with psoriasis. Interleukin (IL)-17A levels and T helper (Th)1/Th17 pathway enrichment were comparable between diseases, while HS presented greater tumour necrosis factor- and IL-1ß-related signalling. The Th17-associated markers peptidase inhibitor 3 (PI3) and lipocalin 2 (LCN2) were able to differentiate psoriasis from HS accurately. 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. Despite the greater body surface area involved in psoriasis, HS presents a greater serum inflammatory burden.

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.

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.

Malignancy and infection risk during adalimumab therapy in hidradenitis suppurativa.

BACKGROUND: The association of adalimumab therapy with malignancy and infection is established in other inflammatory diseases; however, rates of hidradenitis suppurativa (HS) are based on case reports or retrospective healthcare data and the effect of adalimumab therapy on these rates is unknown. Previously reported rates in the PIONEER OLE Phase 3 study reported on rates only in a subpopulation of 88 participants rather than the entire cohort. AIM: To quantify rates of malignancy and serious infection in all patients with HS treated with adalimumab 40 mg weekly. METHODS: Reanalysis was undertaken of individual patient data from the PIONEER 1, PIONEER 2 and PIONEER open-label extension Phase 3 trial data encompassing 591 unique patients with HS administered adalimumab 40 mg weekly without concurrent antibiotic exposure. Incidence rates of serious infection and malignancy were calculated. RESULTS: Incidence rates of serious infection and malignancy were 2.14 and 0.46 per 100 patient-years, respectively. Rates of infection and malignancy were comparable to those in other inflammatory conditions examined. CONCLUSION: Incidence of serious infection in patients with HS on adalimumab is comparable to those with psoriasis and inflammatory arthropathies, but the incidence of malignancy is increased. This may reflect disease-specific malignancy risk rather than an effect of adalimumab.

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.

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.

A systematic review and critical evaluation of reported pathogenic sequence variants in hidradenitis suppurativa.

Hidradenitis suppurativa (HS) is a severe chronic inflammatory disorder characterized by recurrent painful deep-seated nodules with a predilection to the apocrine-bearing areas of skin. A minority of cases of HS are due to mutations in the γ-secretase complex. Contention exists surrounding the pathogenicity of sequence variants and their effects upon Notch signalling. This systematic review was registered with PROSPERO (CRD42016041425) and was conducted in line with the PRISMA statement. Eligibility criteria for this review included published case reports, case series and reviews that identified sequence variants or protein or functional studies from patients with HS. Sixty-two articles were identified reporting a total of 41 sequence variants - heterozygous missense (nine), splice site (nine), insertion resulting in frameshift (one), premature termination codon (19) and promoter region PSTPIP1 (three) - with 18 associated protein or functional studies. The American College of Medical Genetics and Genomics standards and guidelines on the interpretation of sequence variants were applied to each identified variant to assess evidence for pathogenicity. Twenty-three variants were assessed as likely pathogenic, 17 of uncertain significance and one benign. The large number of variants of 'uncertain significance' is largely due to the variable number of functional studies. Four studies used Notch as a proxy for γ-secretase function, with conclusions of nonpathogenicity based on the assumption of Notch signalling as the sole pathogenic process. The role of Notch-independent signalling mechanisms requires further research. Limitations to this study include identification of variants of Mendelian inheritance and not complex polygenic traits.