Different HS phenotypes and their management – Joana Cabete (Portugal)

Hidradenitis suppurativa (HS) is a heterogenous disease, exhibiting high variability in clinical morphology, involved areas, and response to medical treatment. This has prompted the search for clinical patterns, or phenotypes, in an effort to improve disease management and to better predict outcomes.
In 2013 Canoui-Poitrine et al. first proposed a phenotypic HS classification. Since then, other clinical classifications have been suggested. However, most proposed phenotypes do not translate into prognosis or different disease management. Additionally, inter-rater reliability of these phenotypes appears to be unsatisfactory, therefore limiting its interest in daily practice.
More recently, the genotype-endotype-phenotype relationships have been explored. The Frew et al. analysis showed the lack of correlation between existing phenotypic classifications and the few genetic mutations currently associated with HS. Conversely, González-Manso et al., in 2021, were able to describe two clusters or HS endotypes, connecting clinical presentation to serum interleukins and gamma-secretase mutations.
While there are still many gaps in our understanding of HS pathophysiology, the investigation into the relationships between polymorphisms, molecular endotypes, and phenotypes is our present and future, and appears fundamental to the identification of variables / biomarkers of disease activity and of response to medical treatment.

Microbiota and biofilm – Aude Nassif (France)

A specific microbiome and the presence of biofilms have been recently identified in Hidradenitis Suppurativa (HS) lesional skin. A few studies also looked into unaffected skin folds and gut microbiota in hidradenitis suppurativa patients. 
The lecture on microbiota and biofilm will give the latest information about HS lesional, non lesional skin and gut microbiota, including biofilms, as well as focus on the microbiota isolated in some inflammatory diseases generally associated with HS, demonstrating some unexpected similarities.

Antibiotic therapy in HS – Luca Bianchi (Italy)

Hidradenitis Suppurativa (HS) is a chronic, inflammatory, debilitating skin disease of the terminal follicles in apocrine gland-rich areas. The role of skin dysbiosis, biofilm-associated-bacteria, bacterial infections or superinfections is still debated. They could alter the host inflammatory response, release DAMPs, PAMPs and pro-inflammatory cytokines, promote autoinflammation and participate the HS progression, localization and clinical manifestations. Effectiveness of antibiotics, due to antimicrobial, anti-inflammatory and immunomodulatory properties, suggest the role of triggering microbial factors. Antibiotics exert direct and indirect actions against bacterial load and counteract inflammosome, angiogenesis, chemiotaxis and granuloma formation. This lecture will review topical and systemic antibiotics in HS, long-term safety and risk factors related to response to treatment and number of flares.
Duration and frequency of antibiotic use should balance the benefit with the risk of antibiotic resistance. 
Considering the significant risk of further increase in resistance rates, acquisition of bacterial antibiotic sensitivity profiles should be recommended when HS purulent material is available. Future prospective studies on antibiotic resistance patterns, microbiome characteristics and their relationships with different HS therapies, including antibiotics, immunomodulatory drugs and biological therapies are awaited.

Management of severe HS – Simon Francis Thomsen (Denmark)

HS has a substantial negative impact on the quality of life, and until recently, only few treatments and surgical procedures had the potential to fundamentally change the outlook of patients with HS. However, recent advances in the understanding of HS pathophysiology, and in particular, the advent of biologic drugs and small molecule inhibitors, has improved the therapeutic perspective for patients with HS. 
This lecture will offer insights on the link between pathophysiology and choice of treatment and an overview of the therapeutic options. Moreover, it will also focus on the patient journey and treatment ladder, on the strategies for immunoinflammatory treatments and on novel treatment targets.