Hidradenitis suppurativa (HS), known as acne inversa, is a chronic inflammatory skin disorder characterized by recurrent nodules, abscesses, and sinus tracts. HS most commonly affects the axillary, inguinal, and anogenital regions. The course of the disease can persist for decades.
The chronic and recurrent inflammation of HS, which is similar to that in Crohn’s disease (CD), finally leads to fistula and sinus tracts. Ostlere et al[1] first noticed a high risk of HS in patients with CD in the 1990s. Subsequently, several reported cases indicated similar pathologic features[2,3] and genetic susceptibility[4] between HS and CD. Later, patients with HS with simultaneous CD symptoms were significantly relieved by treatment with anti-tumor necrosis factor-alpha inhibitors (anti-TNF-α). Anti-TNF-α therapy not only promoted great progress in the treatment of HS but also manifested the possible common pathogenesis of HS and CD[5]. In addition, some studies found that both HS and CD shared the same immune dysregulation mechanism, such as significantly increased interleukin-1 (IL-1), IL-6, IL-17, IL-23, and TNF[6,7]. According to similar clinical and histological characteristics, as well as the intersections of pathogenesis and treatment, it is widely accepted that there may be a strong association between CD and HS. In this review, we summarize the recent studies focused on the association between HS and CD.