Case Presentation: A 52-year-old woman with hidradenitis suppurativa (HS), previously unresponsive to multiple topical and oral antibiotics, was escalated to Secukinumab. Shortly after initiation, she developed five weeks of progressively worsening bloody diarrhea. A colonoscopy at an outside hospital showed findings concerning for ulcerative colitis (UC), and she was started on prednisone 60 mg daily, but her symptoms worsened during taper. On presentation, laboratory studies showed Hemoglobin 8.7 g/dL, Sodium 134 mmol/L, Creatinine 0.6 mg/dL, BUN 3 mg/dL, and a markedly elevated CRP 164.4 mg/L. CT abdomen and pelvis revealed diffuse, persistent colitis. Considering the growing evidence that Secukinumab may precipitate or exacerbate UC, the medication was promptly discontinued. She was started on IV steroids and mesalamine suppositories. Repeat colonoscopy demonstrated continuous erythema, loss of vascularity, and deep ulcerations from rectum to cecum, confirming severe pancolitis. She remained refractory to Infliximab, despite dose intensification, and to Upadacitinib, with persistent hematochezia and abdominal pain. Due to failure of maximal medical therapy, she underwent total abdominal colectomy with end ileostomy and was initiated on TPN, leading to postoperative improvement.
Discussion: HS is a chronic inflammatory skin disorder typically treated first with antibiotics; biologic therapy is reserved for moderate to severe disease. Secukinumab, an IL-17A inhibitor, has demonstrated efficacy in HS, but may disrupt gastrointestinal mucosal immunity. IL-17 plays a key protective role in epithelial repair and barrier maintenance; thus, its inhibition has been linked to new-onset or worsened Inflammatory Bowel Disease (IBD). This case highlights a dramatic and rapidly progressive course of UC following initiation of Secukinumab. Despite treatment with high-dose corticosteroids, anti-TNF therapy, and JAK inhibition, the disease remained fulminant, ultimately requiring surgical intervention. The clinical trajectory underscores the importance of early recognition of biologic-associated colitis in HS patients receiving IL-17 blockade.
Conclusions: This case highlights a rare but clinically significant association between Secukinumab and the onset of IBD including severe, medically refractory Ulcerative Colitis. Although IL-17A inhibitors offer meaningful benefit for moderate to severe HS, current evidence is limited to a small number of reported cases, suggesting a potential risk of inducing or unmasking IBD. Early recognition is critical and clinicians should maintain vigilance for new gastrointestinal symptoms, ensure appropriate baseline screening, and promptly discontinue secukinumab if IBD is suspected. Larger studies and robust post-marketing surveillance are needed to better define this emerging safety signal and guide optimal biologic selection in high-risk patients.