Hidradenitis Suppurativa: Where We Are and Where We Are Going

Abstract

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease primarily affecting apocrine gland-rich areas of the body. It is a multifactorial disease in which genetic and environmental factors play a key role. The primary defect in HS pathophysiology involves follicular occlusion of the folliculopilosebaceous unit, followed by follicular rupture and immune responses. Innate pro-inflammatory cytokines (e.g., IL-1β, and TNF-α); mediators of activated T helper (Th)1 and Th17 cells (e.g., IFN-γ, and IL-17); and effector mechanisms of neutrophilic granulocytes, macrophages, and plasma cells are involved. On the other hand, HS lesions contain anti-inflammatory mediators (e.g., IL-10) and show limited activity of Th22 cells. The inflammatory vicious circle finally results in pain, purulence, tissue destruction, and scarring. HS pathogenesis is still enigmatic, and a valid animal model for HS is currently not available. All these aspects represent a challenge for the development of therapeutic approaches, which are urgently needed for this debilitating disease. Available treatments are limited, mostly off-label, and surgical interventions are often required to achieve remission. In this paper, we provide an overview of the current knowledge surrounding HS, including the diagnosis, pathogenesis, treatments, and existing translational studies.

Keywords: diagnosis; hidradenitis suppurativa; pathogenesis; translational studies; treatments.

Figure 1

Clinical images of typical HS lesions in groin (A), and axilla (B,C). Superficial papules, small abscesses without scarring or sinus tracts, Hurley stage I (A). Multiple, recurrent abscesses with initial sinus tracts and cicatrization, Hurley stage II (B). Diffuse involvement of the axillary region with large abscesses, interconnected tracts, and scarring, Hurley stage III (C).

Figure 2

Typical histological features of HS. Sample acquired by punch biopsy from gluteal region. Hyperparakeratosis and papillomatosis (1), follicular hyperkeratosis and perifolliculitis (2), fibrosis (3), abscess-like accumulation of neutrophils and spotted infiltrate of lymphocytes/plasma cells (4), epithelialized sinus tract with surrounding inflammatory reaction (5).

Figure 3

Pathophysiology of HS: a schematic overview.