The Roles of Keratinocytes in the Initiation, Progression and Maintenance of Hidradenitis Suppurativa.

Hidradenitis suppurativa (HS) is an autoinflammatory skin disease characterised by deep-seated and painful nodules, abscesses and draining tunnels that extensively penetrate the dermis in the axillae, inguinal and gluteal areas. The exact aetiology remains unclear. However, current evidence suggests that HS originates from an intrinsic defect within the hair follicle, leading to follicular obstruction, cyst development and eventual rupture, which triggers an inflammatory reaction. The initiation, progression and maintenance of the disease may involve functional abnormalities in keratinocytes (KCs), significantly contributing to the production of proinflammatory cytokines within and around the affected tissue and increased infiltration of immune cells. This review synthesises current evidence on KCs in HS, emphasising their genetic background and metabolic dysregulation. It comprehensively evaluates the cytokine milieu influenced by KCs within affected tissues. Notably, it highlights the diverse phenotypes of KCs within draining tunnels, underscoring their heterogeneity and implications for disease progression.