Risk Factors for Developing Hidradenitis Suppurativa in Patients With Inflammatory Bowel Disease: A Retrospective Case–Control Study

BACKGROUND: Hidradenitis suppurativa (HS) is associated with inflammatory bowel disease (IBD), though risk factors remain to be determined. AIM: To characterize HS among a cohort of IBD patients and identify risk factors for its development. METHODS: This was a retrospective case–control study at the ambulatory IBD centre at Mount Sinai Hospital from inception to May 2019. Patients with IBD who developed HS were included. Cases were matched 5:1 by age, gender (male versus female) and IBD type (ulcerative colitis [UC] or Crohn’s disease [CD]) to controls who had IBD without HS. Conditional logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (95% CIs). RESULTS: Twenty-nine cases of HS (19 CD and 10 UC) and 145 controls were included. Of the 29 patients with HS, 11 (37.9%) were male and 18 (62.1%) were female. The severity of HS was mild in 10 (34.5%), moderate in 16 (55.2%) and severe in 3 (10.3%) patients. Patients with HS and IBD were more likely to be active (OR 10.3, 95% CI 2.0 to 54.0, P = 0.006) or past (OR 8.4, 95% CI 2.7 to 25.8, P < 0.005) smokers. Patients with HS and IBD were also more likely to have active endoscopic disease (OR 3.8, 95% CI 1.2 to 12.2, P = 0.022). Furthermore, those with HS and CD were more likely to have active perianal disease (OR 21.1, 95% CI 6.2 to 71.9, P < 0.005). CONCLUSIONS: Active IBD, perianal disease and smoking may be associated with HS in IBD. Larger studies are needed to better characterize this morbid condition.