IL17A and hidradenitis suppurativa: Hidradenitis suppurativa is a chronic, inflammatory, debilitating skin disease that affects hair follicles and is characterized by significant skin infiltration of CD161- and IL-17-expressing Th17 cells.188 Secukinumab has moderate efficacy in patients with hidradenitis suppurativa based on open-label pilot clinical trials, and phase III trials are currently being conducted.189 Two open-label trials of brodalumab, an IL-17 receptor antagonist, have shown that it may be effective in patients who have not benefited from multiple biologics.