Long-standing refractory hidradenitis suppurativa responded to a brodalumab monotherapy in a patient with psoriasis: A possible involvement of Th17 across the spectrum of both diseases

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic inflammatory skin disease mainly affecting apocrine gland-rich areas of the body with painful nodules, persisted abscess, sinus tracts, and scarring. The etiopathology of HS remains unclearly understood, but the disease is considered as a polygenic autoinflammation condition originating from follicular hyperkeratosis and occlusion. Recent advances concerning the substantial roles of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-17, and IL-23 have accelerated in developing a repertoire of therapeutic biologics in HS. Currently five biologics antagonistic for these different cytokines, adalimumab, anakinra, etanercept, infliximab, and ustekinumab, have been explored in the treatment setting of HS; however, only limited evidence is available for the therapeutic advantage of IL-17 pathway blockade. We present a 47-year-old Japanese man who had a long-standing, debilitating HS complicated with psoriasis, both of which were refractory to a series of the standard treatment. Not only psoriatic skin but also HS lesions responded dramatically to brodalumab, an IL-17 receptor antagonist, accompanied with decrease of validated assessments, namely the Hurley's staging classification and modified Sartorius score. Brodalumab was well tolerated with rapid improvement and no adverse reaction, and finally gave a satisfactory maintenance of disease remission. To our best knowledge, this is the first successful use of anti-IL-17 receptor antibody in a Japanese case with coexistence of HS and psoriasis. We also discuss extending understanding of the potential benefit and current limitation of brodalumab in the treatment of HS.