NOD2 signalling in hidradenitis suppurativa

Cytokine-Mediated Molecular Pathophysiology of Hidradenitis Suppurativa: A Narrative Review

Background

Hidradenitis suppurativa (HS) is a chronic inflammatory condition of the skin that mainly affects the apocrine gland-rich intertriginous areas. The disease manifests as painful nodules, abscesses, and pus-filled tunnels, which can severely impact patient's quality of life. While diagnosis is clinical, successful treatment options for this condition are limited. There has been an increase in research and clinical trials focusing on biomarkers and cytokines for clinical use. Understanding the potential biomarkers and cytokines implicated in HS pathogenesis may allow efficacious and safe treatment options.

Summary

A literature review was conducted on nine biomarkers and cytokines. IL-1, IL-10, IL-17, IL-23, TNF-α, YKL-40, G-CSF, NOD2, and the complement system were identified due to their potential clinical utilization and pathophysiological involvement in HS.

Key Messages

With further research expanding our understanding of the pathophysiology of HS and the roles these cytokines and biomarkers play, there is potential for utilization as diagnostic markers or development of antagonists against these specific agents for HS management.

The genetic aspects of hidradenitis suppurativa

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

Anemia and Systemic Inflammatory Markers in Patients with Perianal Disease: Hidradenitis Suppurativa and Inflammatory Bowel Disease

BACKGROUND

Hidradenitis suppurativa (HS) and inflammatory bowel disease (IBD) have been reported to have a wide variety of overlaps in their pathogenesis, laboratory findings, and histopathology. These two diseases can form draining tunnels and are difficult to differentiate, particularly from fistulizing lesions in the perianal area.

OBJECTIVE

This retrospective study of HS and IBD patients with perianal lesions sought to analyze the anemia and systemic inflammation biomarkers in these disease groups.

METHODS

A retrospective chart review was conducted on the laboratory findings of a total of 212 patients with perianal disease - 72 with HS, 78 with IBD, and 62 with both HS and IBD - who were evaluated at Mayo Clinic between 1998 and 2021.

RESULTS

In the HS group, 45.8% of males and females were anemic, compared to 58.1% of males and 73.5% of females in the IBD group. The HS + IBD group had the highest prevalence of anemia and the lowest hemoglobin levels. The odds ratio for being anemic was 2.19 for the IBD group and 4.05 for the IBD + HS group compared to the HS group. Monocyte/lymphocyte ratio (MLR) and platelet/lymphocyte ratio (PLR) were significantly higher in the IBD group, whereas neutrophil/lymphocyte ratio (NLR) was significantly higher in the IBD + HS group.

CONCLUSION

Our data show for the first time the prevalence of anemia in patients with HS and IBD who have perianal lesions. In addition, noninvasive biomarkers using complete blood counts such as MLR, PLR, and NLR could be useful not only in differentiating perianal HS from fistulizing perianal IBD but also in selecting treatment.

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.