Dynamic Leukocyte Populations Are Associated With Early- and Late-stage Lesions in Hidradenitis Suppurativa

Biology of Interleukin-17 and Novel Therapies for Hidradenitis Suppurativa

Skin disorders affect ∼40% of the human population. One of the most debilitating cutaneous disorders is Hidradenitis suppurativa (HS), a noncommunicable chronic inflammatory disease with an estimated global prevalence of 0.4% to 2.5%. In January 2011, high levels of IL-17 were discovered in skin lesions of HS patients. In the following years, translational and clinical research led to a better understanding of the pathogenesis of HS. In June 2023, more than 12 years after the initial note, secukinumab, an anti-IL-17A monoclonal antibody, was approved for the treatment of moderate to severe HS. This is the next milestone in improving the treatment of these patients after the approval of the anti-TNF-α monoclonal antibody adalimumab in 2015. In this review article, we present the IL-17 pathway in HS and discuss the use of secukinumab as a therapeutic option for this disease. Our review starts with a description of the epidemiology, clinical features, etiology, and pathogenesis of HS. An overview of the IL-17/IL-17 receptor system in general and a detailed description of the known facts about the expression and action of IL-17 in HS follow. Afterward, we consider the results of clinical trials evaluating the safety and efficacy of IL-17 inhibitors in HS. Finally, a comparison is made between secukinumab and adalimumab and the characteristics of the patients that may be particularly suitable for each of these biologics are described.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Serum Immunoglobulin G Is a Marker of Hidradenitis Suppurativa Disease Severity

Hidradenitis suppurativa (HS) is a chronic inflammatory condition of the skin that is brought about by autoinflammation and hyperkeratosis at the pilosebaceous unit. The clinical severity of HS can be measured using static (Hurley Severity Scoring (HSS)) and/or dynamic (International HS Severity Scoring System (IHS4)) severity scoring instruments. However, few clinically available serological parameters have been found to correlate with disease severity. In this study, we sought to investigate the role of serum immunoglobulin (Ig) G, M and A levels as biomarkers of disease severity and to compare them with other, more conventional inflammatory indices, such as the erythrocyte sedimentation rate, C-reactive protein, the neutrophil-lymphocyte ratio, the platelet-lymphocyte ratio and the systemic immune-inflammation index. In this cross-sectional study, patients were recruited from the only dermatology referral centre in Malta, Europe, and subjected to clinical examination and the assessment of inflammatory and immunologic parameters. Serum IgG, M and A levels were assessed using the Atellica^® NEPH 630 System (SIEMENS-Healthineers AF, Erlangen, Germany) nephelometric analyser. Serum IgG, M and A levels correlate with both dynamic and static HS severity scoring systems. Serum IgG behaves as a marker of severe HS disease as categorised by HSS and the IHS4. Our findings suggest that the serum IgG level can be used in the clinical setting as a biomarker of disease severity and, therefore, as an adjunct to clinical severity scoring.

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.